<%BANNER%>

New Apparatus Simplifies Design of Modified Atmosphere Packaging Using Perforated Films

Permanent Link: http://ufdc.ufl.edu/UFE0021858/00001

Material Information

Title: New Apparatus Simplifies Design of Modified Atmosphere Packaging Using Perforated Films
Physical Description: 1 online resource (93 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: atmosphere, fiber, films, modified, optic, oxygen, packaging, perforated, respiration, sensor
Agricultural and Biological Engineering -- Dissertations, Academic -- UF
Genre: Agricultural and Biological Engineering thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The overall objective of this project was to design a modified atmosphere package for respiring produce using perforated films. Respiration was measured for sliced rutabaga, sweet potato, squash, squash and zucchini mixture, and turnips. Samples were stored in closed jars at 1, 8, and 15 degrees C. Rutabaga consistently followed a hyperbolic decay trend at all three temperatures. The other products showed hyperbolic decay at the highest temperature but shifted to a linear trend at lower temperatures. Oxygen transmission rate of the commercial package of each product was measured and respiration rate of each product was determined at the recommended temperature and atmosphere of storage to assess the necessity of perforations to the package. It was determined that turnips were the only product that did not require perforations in its packaging. A new apparatus using a fiber optic oxygen sensor was developed to measure OTR of perforated films. OTR of holes of 100, 153, 205, and 249 microns were measured at 15, 23, and 30 degrees C. As diameter increased OTR increased and as temperature increased OTR decreased for a particular diameter. Consistent and reproducible measurements using precision orifices provided confidence that the device could be applied to perforations in plastic films, which are not as easily characterized. Packages of broccoli were designed using polyethylene film (2.5 mil thick) with an area of 1050 cm2. A 13.5 gage drill tool was used to perforate packages. Unsteady state methods were used to measure respiration rate of broccoli at 4 degrees C. Ten packages were stored at 4 degrees C and allowed to reach steady state. Required OTR to maintain package at average steady state O2 concentration was calculated using experimentally derived respiration rate and literature values, which were of similar orders of magnitude. Package OTR was measured in two parts, a non-perforated portion and a perforated portion. Non-perforated OTR was measured in the typical way at 20 and 30 degrees C. OTR at 4 degrees C was determined by extrapolation of the Arrhenius temperature sensitivity relationship. Perforated film OTR was measured at 4 degrees C using our new apparatus. Total measured OTR was calculated by adding perforated OTR and non-perforated OTR. Perforation region accounted for the majority of the OTR. Measured OTR agreed well with required calculated values of OTR suggesting the new apparatus is a valuable tool for designing modified atmosphere packaging of fresh produce using perforated films.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.E.)--University of Florida, 2008.
Local: Adviser: Welt, Bruce A.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0021858:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021858/00001

Material Information

Title: New Apparatus Simplifies Design of Modified Atmosphere Packaging Using Perforated Films
Physical Description: 1 online resource (93 p.)
Language: english
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: atmosphere, fiber, films, modified, optic, oxygen, packaging, perforated, respiration, sensor
Agricultural and Biological Engineering -- Dissertations, Academic -- UF
Genre: Agricultural and Biological Engineering thesis, M.E.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: The overall objective of this project was to design a modified atmosphere package for respiring produce using perforated films. Respiration was measured for sliced rutabaga, sweet potato, squash, squash and zucchini mixture, and turnips. Samples were stored in closed jars at 1, 8, and 15 degrees C. Rutabaga consistently followed a hyperbolic decay trend at all three temperatures. The other products showed hyperbolic decay at the highest temperature but shifted to a linear trend at lower temperatures. Oxygen transmission rate of the commercial package of each product was measured and respiration rate of each product was determined at the recommended temperature and atmosphere of storage to assess the necessity of perforations to the package. It was determined that turnips were the only product that did not require perforations in its packaging. A new apparatus using a fiber optic oxygen sensor was developed to measure OTR of perforated films. OTR of holes of 100, 153, 205, and 249 microns were measured at 15, 23, and 30 degrees C. As diameter increased OTR increased and as temperature increased OTR decreased for a particular diameter. Consistent and reproducible measurements using precision orifices provided confidence that the device could be applied to perforations in plastic films, which are not as easily characterized. Packages of broccoli were designed using polyethylene film (2.5 mil thick) with an area of 1050 cm2. A 13.5 gage drill tool was used to perforate packages. Unsteady state methods were used to measure respiration rate of broccoli at 4 degrees C. Ten packages were stored at 4 degrees C and allowed to reach steady state. Required OTR to maintain package at average steady state O2 concentration was calculated using experimentally derived respiration rate and literature values, which were of similar orders of magnitude. Package OTR was measured in two parts, a non-perforated portion and a perforated portion. Non-perforated OTR was measured in the typical way at 20 and 30 degrees C. OTR at 4 degrees C was determined by extrapolation of the Arrhenius temperature sensitivity relationship. Perforated film OTR was measured at 4 degrees C using our new apparatus. Total measured OTR was calculated by adding perforated OTR and non-perforated OTR. Perforation region accounted for the majority of the OTR. Measured OTR agreed well with required calculated values of OTR suggesting the new apparatus is a valuable tool for designing modified atmosphere packaging of fresh produce using perforated films.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis: Thesis (M.E.)--University of Florida, 2008.
Local: Adviser: Welt, Bruce A.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-05-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0021858:00001


This item has the following downloads:


Full Text

PAGE 1

1 NEW APPARATUS SIMPLIFIES DESIGN OF MODIFIED ATMOSPHERE PACKAGING USING PERFORATED FILMS By AYMAN ABDELLATIEF A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2007

PAGE 2

2 2007 Ayman Abdellatief

PAGE 3

3 To my friends and family whose support helped made this possible

PAGE 4

4 ACKNOWLEDGMENTS I show my appreciation to my advisor Dr Bruce Welt whose support made this project possible. I am grateful to my committee members Dr. Murat O Balaban for his guidance and Dr. David W Hahn and his graduate st udent Leia Coffey for their assistance. I thank my colleague Fernando Vargas for his guidance and friendship. I express my gratitude to Steve Feagle whose technical expertise was very valu able for this research.I show my sincere appreciation to the University of Florida and the Agricultural a nd Biological Engineering Department for their funding and support.

PAGE 5

5 TABLE OF CONTENTS Page ACKNOWLEDGMENTS...............................................................................................................4 LIST OF TABLES................................................................................................................. ..........7 LIST OF FIGURES................................................................................................................ .........9 NOMENCLATURE................................................................................................................... ...12 ABSTRACT....................................................................................................................... ............14 CHAPTER 1 INTRODUCTION..................................................................................................................16 Modified Atmosphere Packaging...........................................................................................16 Mathematical Modeling of Modified Atmosphere Packaging...............................................16 Permeation Theory..........................................................................................................16 Modeling of Modified Atmosphere Packaging...............................................................18 2 DETERMINING THE NECESSITY OF PE RFORATIONS FOR COMMERCIALLY PACKAGED PRODUCE.......................................................................................................21 Introduction................................................................................................................... ..........21 Respiration.................................................................................................................... ...21 Permeation..................................................................................................................... ..22 Ideal Storage Conditions.................................................................................................23 Objectives..................................................................................................................... ...24 Materials and Methods.......................................................................................................... .24 Headspace Analysis.........................................................................................................24 Oxygen Transmission Rates of the Package...................................................................25 Product Respiration Rates...............................................................................................25 Results and Discussion......................................................................................................... ..26 Headspace...................................................................................................................... ..26 Respiration and Package Oxygen Transmission Rate.....................................................26 Example of How to Calculate Respir ation Rate from Respiration Data.........................29 3 METHOD FOR MEASURING THE OXY GEN TRANSMISSION RATE OF PERFORATED FILMS..........................................................................................................31 Introduction................................................................................................................... ..........31 Theory......................................................................................................................... .....32 Oxygen Transmission Rate (OTR) Measurements..........................................................35 Non-perforated films................................................................................................35 Perforated films........................................................................................................36

PAGE 6

6 Fiber optic oxygen sensor........................................................................................36 Materials and Methods.......................................................................................................... .37 Measurement of Samples................................................................................................38 Recalculating Diffusion Coefficients..............................................................................39 Results and Discussion....................................................................................................39 4 NEW APPARATUS SIMPLIFIES DE SIGN OF MODIFIED ATMOSPHERE PACKAGING WITH PERFORATED FILMS......................................................................42 Introduction................................................................................................................... ..........42 Materials and Methods.......................................................................................................... .42 Broccoli Package OTR....................................................................................................43 Modified Atmosphere Package Design with Perforations..............................................43 Results and Discussion......................................................................................................... ..44 Headspace of Commercially Packaged Broccoli............................................................44 Respiration of Broccoli....................................................................................................44 Broccoli Package OTR....................................................................................................46 Broccoli Package Performance Data...............................................................................46 Prediction of OTR Package using Design Equation........................................................48 5 CONCLUSIONS....................................................................................................................49 APPENDIX A RESPIRATION DATA FOR THE FIVE RESPIRING PRODUCTS...................................52 B OXYGEN TRANSMISSION RATE OF PRECISION ORIFICES.......................................82 C BROCCOLI PACKAGE DATA............................................................................................88 REFERENCES..................................................................................................................... .........90 BIOGRAPHICAL SKETCH.........................................................................................................93

PAGE 7

7 LIST OF TABLES Table page 1-1 Gas Permeabilities of various polymers used in Modified Atmosphere Packaging (Robertson 1993)...............................................................................................................18 2-1 Headspace data from bagged samples...............................................................................26 2-2 Oxygen respiration coefficients.........................................................................................28 2-3 Required OTR at design temp erature and desired O2 level..............................................29 3-1 Oxygen diffusion coefficient in air calc ulated from precision orifices and Perrys Chemical Engineering Handbook......................................................................................40 4-1 Respiration coefficients for oxygen and carbon dioxide for broccoli................................46 A-1 Rutabaga respiration data 15C..........................................................................................52 A-2 Rutabaga respiration data 8C............................................................................................54 A-3 Rutabaga respiration data 1C............................................................................................56 A-4 Sweet Potato respiration data 15C....................................................................................58 A-5 Sweet Potato respiration data 8C......................................................................................60 A-6 Sweet Potato respiration data 1C......................................................................................62 A-7 Squash respiration data 15C.............................................................................................64 A-8 Squash respiration data 8C...............................................................................................66 A-9 Squash respiration data 1C...............................................................................................68 A-10 Squash and Zucchini respiration data 15C.......................................................................70 A-11 Squash and Zucchini respiration data 8C.........................................................................72 A-12 Squash and Zucchini respiration data 1C...........................................................................74 A-13 Turnip respiration data 15C..............................................................................................76 A-14 Turnip respiration data 8C............................................................................................... .78 A-15 Turnip respiration data 1C............................................................................................... .80 B-1 OTR of precision orifices at 15, 23, and 30C...................................................................82

PAGE 8

8 C-1 Commercially Packaged Broccoli Head Space Samples...................................................88 C-2 Broccoli Respiration Data..................................................................................................89

PAGE 9

9 LIST OF FIGURES Figure page 1-2 Atmosphere of packaged tomatoes over time. The top curve indicates the CO2 concentration while the bottom curve indi cates the oxygen concentration over time.......20 2-1 Actual data logger results for sample shipment from commercial producer to University of Florida..........................................................................................................24 2-2 Unsteady state respirati on data for Rutabaga at 15 C, % vs time.....................................27 2-3 Unsteady state respirati on data for Rutabaga at 15 C, cc/g vs time..................................27 3-1 Typical apparatus for measuring OTR using coulometric method....................................32 3-2 Unsteady state measurement of headspace over time........................................................33 3-3 Schematic Profile of OTR chamber...................................................................................38 3-4 Plot used to determine OTR of hole/perforation 249m hole at 300C..............................39 3-5 OTR of holes vs. temperature............................................................................................40 4-1 Unsteady state respirati on data for Broccoli at 4 C % vs time..........................................45 4-2 Unsteady state respirati on data for Broccoli at 4 C cc/g...................................................45 4-2 Plot used to determine OT R of hole/perforation at 40C....................................................47 4-3 Broccoli packages reaching steady state............................................................................47 A-1 Rutabaga 15C, % vs time.................................................................................................53 A-2 Rutabaga 15C, cc/g vs time..............................................................................................53 A-3 Rutabaga 8C, % vs time....................................................................................................55 A-4 Rutabaga 8C cc/g vs time.................................................................................................55 A-5 Rutabaga 1C, % vs time....................................................................................................57 A-6 Rutabaga 1C, cc/g vs time................................................................................................57 A-7 Sweet Potato 15C, % vs time............................................................................................59 A-8 Sweet Potato 15C, cc/g vs time........................................................................................59 A-9 Sweet Potato 8C, % vs time..............................................................................................61

PAGE 10

10 A-10 Sweet Potato 8C, cc/g vs time..........................................................................................61 A-11 Sweet Potato 1C, % vs time..............................................................................................63 A-12 Sweet Potato 1C, cc/g vs time..........................................................................................63 A-13 Squash 15C, % vs time.................................................................................................... .65 A-14 Squash 15C, cc/g vs time................................................................................................. .65 A-15 Squash 8C, % vs time..................................................................................................... ..67 A-16 Squash 8C, cc/g vs time.................................................................................................. ..67 A-17 Squash 1C, % vs time..................................................................................................... ..69 A-18 Squash 1C, cc/g vs time.................................................................................................. ..69 A-19 Squash and Zuchini 15C, % vs time.................................................................................71 A-20 Squash and Zuchini 15C, cc/g vs time..............................................................................71 A-21 Squash and Zuchini 8C, % vs time...................................................................................73 A-22 Squash and Zuchini 8C, cc/g vs time................................................................................73 A-23 Squash and Zuchini 1C, % vs time...................................................................................75 A-24 Squash and Zuchini 1C, cc/g vs time................................................................................75 A-25 Turnips 15C, % vs time................................................................................................... .77 A-26 Turnips 15C, cc/g vs time................................................................................................ .77 A-27 Turnips 8C, % vs time.................................................................................................... ..79 A-28 Turnips 8C, cc/g vs time................................................................................................. ..79 A-29 Turnips 1C, % vs time.................................................................................................... ..81 A-30 Turnips 1C, cc/g vs time................................................................................................. ..81 B-1 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 15C............................................................82 B-2 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 15C............................................................82 B-3 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 15C............................................................83 B-4 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 15C............................................................83

PAGE 11

11 B-5 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 23C............................................................84 B-6 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 23C............................................................84 B-7 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 23C............................................................85 B-8 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 23C............................................................85 B-9 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 30C............................................................86 B-10 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 30C............................................................86 B-11 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 30C............................................................87 B-7 -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 30C............................................................87

PAGE 12

12 NOMENCLATURE A area of package (cm2) Ah .area of hole (cm2) c1 gas concentration inside package c2 gas concentration outside package J diffusive flux of gas through package (cm3/cm2/s) Jh diffusive flux of gas through perforation (cm3/cm2/s) L package thickness (mil) Lh perforation thickness (cm) OTRnon perf oxygen transmission rate (cc/cm2/day) for non-perforated package OTR perf oxygen transmission rate (cc/da y) for perforated package 2inOp partial pressure of oxygen inside package 2outOp partial pressure of oxygen outside package 2inCOp partial pressure of carbo n dioxide inside package 2outCOp partial pressure of carbo n dioxide outside package 2inNp partial pressure of nitrogen inside package 2outNp partial pressure of nitrogen outside package p1 partial pressure of gas inside package p2 partial pressure of gas outside package P gas permeability coefficient (cc-mil/cm2/day) 2OP oxygen permeability coefficient (cc-mil/cm2/day)

PAGE 13

13 2COP carbon dioxide permeability coefficient (cc-mil/cm2/day) 2NP nitrogen permeability coefficient (cc-mil/cm2/day) Rh radius of perforation (cm) 2OR respiration rate of oxygen (cc/g/day) 2COR respiration rate of car bon dioxide (cc/g/day) S Henrys Law gas solubility coefficient t time (days) V volume of package (cc) W weight of product in package (g)

PAGE 14

14 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering NEW APPARATUS SIMPLIFIES DESIGN OF MODIFIED ATMOSPHERE PACKAGING USING PERFORATED FILMS By Ayman Abdellatief May 2008 Chair: Bruce Welt Major: Agricultural and Biological Engineering The overall objective of this project was to design a modified atmosphere package for respiring produce using perforated films. Respir ation was measured for sliced rutabaga, sweet potato, squash, squash and zucchini mixture, and turnips. Samples were stored in closed jars at 1, 8, and 15C. Rutabaga consistently followed a h yperbolic decay trend at all three temperatures. The other products showed hyperbolic decay at th e highest temperature but shifted to a linear trend at lower temperatures. Oxygen transmission rate of the commerci al package of each product was measured and respiration rate of each product was determined at the recommended temperature and atmosphere of storage to assess th e necessity of perforations to the package. It was determined that turnips we re the only product that did not require perforations in its packaging. A new apparatus using a fibe r optic oxygen sensor was developed to measure OTR of perforated films. OTR of holes of 100, 153, 205, and 249 m were measured at 15, 23, and 30C. As diameter increased OTR increased and as temperature increased OTR decreased for a particular diameter. Consistent and reproducible measurements us ing precision orifices provided confidence that the device could be applied to perforations in plastic f ilms, which are not as easily characterized.

PAGE 15

15 Packages of broccoli were designed using polye thylene film (2.5 mil thick) with an area of 1050 cm2. A 13.5 gage drill tool was used to perf orate packages. Unsteady state methods were used to measure respiration rate of broccoli at 4C. Ten packages were stored at 4C and allowed to reach steady state. Required OTR to ma intain package at average steady state O2 concentration was calculated using experimentally derived respirati on rate and literature values, which were of similar orders of magnitude. Package OTR was measured in two parts, a nonperforated portion and a perforat ed portion. Non-perforated OT R was measured in the typical way at 20 and 30C. OTR at 4C was determined by extrapolation of the Arrhenius temperature sensitivity relationship. Perfor ated film OTR was measured at 4C using our new apparatus. Total measured OTR was calculated by adding perforated OTR and non-perforated OTR. Perforation region accounted for the majority of the OTR. Measured OTR agreed well with required calculated values of OT R suggesting the new apparatus is a valuable tool for designing modified atmosphere packaging of fresh produce using perforated films.

PAGE 16

16 CHAPTER 1 INTRODUCTION Modified Atmosphere Packaging Consumer demand for fresh and convenient f oods has led to the growth of modified atmosphere packaging (MAP) as a technique to improve product image, reduce waste, and extend the shelf life of a wide ra nge of foods (Martinez-Ferrer et al., 2002). Many fresh products reduce respiration rate due to reduced oxygen concentrati on and increased carbon dioxide concentration, which increases shelf life (Lee et al., 1991). Modifi ed atmospheres must not be too deficient in oxygen in order to avoid anaerobic respiration that can rapidly damage plant tissue, cause fermentation, and produce off flavors (Kader et al., 1989). Additionally, high concentrations of CO2 can also injure pl ant tissues. Therefore, packaging with oxygen transmission rates that match desired respirati on requirements are necessary in order to achieve optimal shelf-life results. Recommended atmosphere s for various fruits and vegetables can be found in the literature (Mannapperuma et al., 1989, Saltveit, 1985). Mathematical Modeling of Modified Atmosphere Packaging Permeation Theory Permeation of a gas through a polymer film is a combination of di ffusion and solubility. A gas will diffuse through a polymer film at a constant rate if a constant concentration gradient is maintained across the film. The di ffusive flux, J, of a gas in a polymer is the amount (Q) passing through a surface of area (A) normal to the direction to the direction of flow during time (t), i.e. A t Q J (1-1) The diffusive flux of a gas through a film is directly proportional to the concentration gradient, L c across a surface of thickness L) ( and is given by Ficks first law:

PAGE 17

17 L c -D J (1-2) Once steady state is achieved equation (1-2) ca n be integrated from the concentration of one surface c1 to the opposite surface c2 across a film of thickness X and is given by: ) c (c D L J2 1 (1-3) which can be re-arranged to L ) c (c D J1 2 (1-4) The right hand side of equation (1-1) can be substituted for the diffusive flux J which yields. L ) c (c D A t Q1 2 (1-5) At sufficiently low concentra tions Henrys law can be a pplied and is expressed as p S c (1-6) Where S is the solubility coefficient and p is the partial pressure of the gas. Equation 6 can be substituted into equation (1-5) which gives. L ) p (p S D A t Q1 2 (1-7) The product D S is the permeability coefficien t and is represented by the symbol P. Yielding L p) ( P A t Q__ (1-8) Which can be rearranged to p) ( A t L Q P__ (1-9)

PAGE 18

18 Four assumptions were made in the deriva tion of the permeability coefficient. The assumptions are that diffusion is at steady state, the concentration gradie nt is linear though the polymer, diffusion takes place in only one di rection, and D and S are independent of concentration (Robertson 1993). The gas permeabil ity of various polymers used in modified atmosphere packaging is shown in Table (1-1) (Robertson 1993).. Table 1-1. Gas Permeabilities of various polym ers used in Modified Atmosphere Packaging Polymer N2O2CO2(P_O2/P_N2)(P_CO2/P_O2)(P_CO2/P_N2) 30C 30C30C Low Density Polyethylene491014200910002.96.418.5 High Density Polyethylene698274090403.93.313.0 Polypropylene-----594023800-----4.0----Poly( vinyl chloride)10331025803.08.325.0 Polystyrene7492840227003.88.030.3 Nylon 625.898.24133.84.216.0 Poly( ethylene terephthlate)12.956.83954.47.030.6 Poly( vinylidene chloride)2.4313.774.95.65.530.9 Mean3.95.823.5 (cc-mil)/(m2day-atm) Modeling of Modified Atmosphere Packaging To maintain a desired atmosphere within a package, rates of gas permeation for a particular gas through the package must match the respiration rate of that gas for that product. At any time the rates of changes in the concentrations of O2, CO2, and N2 per unit volume of free gas space can be expressed as (Wiley, 1994): V W R LV p p A P d t dp2 2out 2in 2 2O O O O O (1-10) V W R LV p p A P d t dp2 2out 2in 2 2CO CO CO CO CO (1-11) LV p p A P dt dp2out 2in 2 2N N N N (1-12) Where [O2], [CO2], and [N2] are the concentrations of O2, CO2, and N2 respectively; 2OP 2COP and 2NP are the permeabilities of the film to O2, CO2, and N2; A is the area of the film; L

PAGE 19

19 is the thickness of the film 2OR, and2COR, the rates of consumption of O2 and production of CO2 respectively; W is the weight of the produce; and V is the headspace volume of the package. When the system reaches steady state, the c oncentration of the gases do not change with time, equations (1), (2), and (3) simplify to L p p A P W R2out 2in 2 2O O O O (1-13) L p p A P W R2out 2in 2 2CO CO CO CO (1-14) 2out 2inN Np p (1-15) Many attempts have been made to mathem atically model the gas atmosphere in a modified atmosphere package. Equations (1-10, 1-11) were simulated numerically by Henig and Gilbert (1975) for packaged tomatoes while Haya kawa et. al. (1975) solved them analytically using Laplace Transforms (Figure 1-2) also for tomatoes. Many respiring products have re spirations rates too high fo r the oxygen transmission rates of most commercially available packaging ma terial. For these products it is necessary to perforate the packages to increase oxygen transm ission rate to a suffici ent level. Diffusion of oxygen through air is about six orders of magnitude greater than permeation through polyethylene films commonly used in packaging. Even a small hole can greatly increase oxygen transmission rate of packaging material. To be able to design a modified atmosphere package for respiring pr oduce, respiration rate of the product must be known at the desired gas composition and storage temperature. Once respiration rate is known, a suitable packagi ng material must be selected. If there is no commercially available packaging material with sufficient oxygen transmission rate, then it becomes necessary to incorporate perforations Therefore it becomes necessary to measure

PAGE 20

20 oxygen transmission rate of the perforated material Unfortunately most of the methods used to measure oxygen transmission rate of packaging materials are not suitable for films with perforations. Figure 1-2. Atmosphere of packaged tomato es over time. The top curve indicates the CO2 concentration while the bottom curve indi cates the oxygen concentration over time The objectives of this work were threefold. The first was to determine the respiration rates of sliced Rutabaga, Sweet Potato, Squash, Squash and Zucchini, and Turnips at optimal storage conditions and to assess the necessity of value added perforations to the commercial packaging for each product. The second was to develop a method to determine the oxygen transmission rates (OTR) of perforated pack aging films. The third was to demonstrate the design of a modified atmosphere package with perforations using the new method and apparatus developed to measure the OTR of perforated films.

PAGE 21

21 CHAPTER 2 DETERMINING THE NECESSITY OF PE RFORATIONS FOR COMMERCIALLY PACKAGED PRODUCE Introduction Fresh produce is particularly challenging to package because products contain living tissues that require adequate gas exchange to remain fresh. Produ ce respiration rate is one of the best measures for prediction of shelf life. Generall y, lower respiration rate translates into longer shelf life. Rate of respirati on typically varies with oxygen c oncentration and inversely with carbon dioxide concentration. The goal of MAP is to design a package that provides an optimal level of oxygen and carbon dioxide transmission to match reduced respiration rate requirements of the produce. Respiration Respiration in fruits and ve getables can be described by the following chemical reaction (Ryall and Pentzer, 1979; 1982): C6H12O6 + 6O2 6CO2 + 6H2O + Energy (2-1) Attempts have been made to model respiration of fruits and vegetables with Michaelis Menten type kinetics with competitive inhib ition of oxygen consumption by the production of carbon dioxide (Lee et al., 1991; Hagger et al., 1992). Lowering the O2 level around fresh fruits and vegetables reduces their respiration rate in proportion to the O2 concentration, but a minimum of about 1-3% O2 is required depending on the commodity. Otherwise respiration will shift from aerobic to anaerobic. The glycolytic pathway replaces the Krebs cycle as the main s ource of energy for the plant tissues. Byproducts such as acetaldehyde and ethanol are formed which give off flavor s and spoil the product (Kader,

PAGE 22

22 1986). Injuring fruit and vegetable ti ssue by slicing generally increas e the respiration rate 3 to 5 fold. The respiration rate also increases 2 to 3 fold as the product ages. (Laties, 1978). Permeation To maintain a desired atmosphere within a package, rates of gas permeation through the package must match respiration demands of products This steady state re lationship is described by Equation (2-2) (Robertson, 1993). L p A P WR (2-2) where W is the weight of produce, R is the respir ation rate of produce (am ount of gas)/(weight of produce x time)), P is the gas permeation coefficient for the gas of interest through the particular plastic at a specifie d temperature (amount of gas x f ilm thickness/(area of film x gas partial pressure difference on either side of the film x time), A is the area of the plastic package, p is partial pressure difference and L is film thickness. Oxygen transmission rate (OTR) is often measured for particular films. OTR is related to permeability, P, via Equation (2-3). L p P OTRperf non (2-3) OTR is often measured using 100% oxygen as th e test gas, which provides the maximum driving force for oxygen transmission (1 atm) and higher analytical resolution. OTR requirements may be predicted for air by combin ing Equations (2-2) and (2-3) by rearranging to form Equation (2-4). 20.9 100 ) p A(0.21 RW OTRinside (2-4)

PAGE 23

23 Where R is respiration rate of produce, W is the weight of th e produce in the package, A is package area, and pinside is the desired partial pressure of oxygen inside the package. Ideal Storage Conditions Determination of ideal storage conditions (tem perature and gas compositions) for products requires extensive experimentation under controll ed conditions. Often, ideal conditions vary considerably for any particular product and may be a function of produce size, geometry, cultivar, season, etc. Theref ore, ideal conditions are better described as ideal ranges of conditions and therefore, package designs tend to be conservative. The following conditions for produce items related to those studied here were found in the literature: Rutabagas. Rutabagas should be stored in an atmosphere of approximately 5% CO2 and > 5% O2 between 1 and 3 C for maximum shelf life (Gorny, 1997). Sweet Potato. Sweet Potatoes should be stored in an atmosphere of approximately 6.5% CO2 and > 12% O2 between 0 and 4 C for maximum shelf life (http://usna.usda.gov/hb66/147f reshcutvegetables.pdf). Squash Squash is highly perishable and should not be stored for more than 2 weeks. Optimal storage conditions are 5 to 10C at 95% RH (Hardenburg et al., 1986). Lower oxygen atmospheres are of no beneficial use for Squash (Leshuk and Saltveit, 1990; Mencarelli et al., 1983). Squash is susceptible to chilli ng injury at temperatures below 50C. (Ryall and Lipton, 1979). Zucchini. Sliced zucchini develops water so aked areas (chilling injury) at 0C and brown discoloration between 5 and 10C, which increases with storage duration. Zucchini slices can be dipped in solutions of CaCl2 alone or with NaOCl. Calcium treatments reduce development of

PAGE 24

24 decay and total microbial growth, and ascorbate loss. Optimal storage conditions for zucchini are 0.25% to 1% oxygen at 0 to 5C (Gorny, 1997). Turnips. Turnips can be held 4 to 5 mo at 0 C (32 F) with 90 to 95% RH. An ideal atmosphere has not been determined for turnips 6 (http://usna.usda.gov/hb66/140turnip.pdf ). Objectives The objectives of this work were to veri fy performance of commercially produced MAP packages and to assess necessity for cost-adding film perforations used to produce certain freshcut product packages. Materials and Methods Headspace Analysis Bagged product samples were shipped to the Univ ersity of Florida vi a overnight delivery in insulated packaging equipped with two freeze r cold packs. Several shipments contained temperature recorders that show ed product enroute approximately 18 hours with temperatures generally between 4 and 10C (Figure 2-1). Figure 2-1. Actual data logge r results for sample shipment from commercial producer to University of Florida. Upon arrival at our laboratory, products were placed in a 1-3C controlled environmental chamber for about 24 to 48 hours prior to use. A dab of silicone sealant was applied to each bag upon arrival in order to create a septum through which a needle was inserted to sample achieved headspace gas compositions of product samples. A headspace analyzer (Pack Check, Mocon,

PAGE 25

25 Inc., Minneapolis, MN) was used to determin e oxygen and carbon dioxide concentrations in sample headspaces. Table 2-1 shows results of headspace measurements. Oxygen Transmission Rates of the Package Two samples from the front panel of the pack age of each product were prepared by cutting a 100 cm2 sample films using a standard cutting die and razor knife. Film sample were then mounted into the oxygen transmission rate analy zer (Oxtran 2/20, Mocon, Inc., Minneapolis, MN). Product Respiration Rates Product respiration rates were measured usi ng an unsteady-state method (Lee et al., 1991; Hagger et al., 1992). Briefly, a given amount of produc t is placed in hermetic ally sealed jars and changes in headspace gas compositions are monitore d over time. Empirical curves are fitted to gas versus time data and mathematical derivative s of these curves (instantaneous slopes), provide respiration rates as a function of gas composition. One liter mason jars were used for unsteady-state respiration experiments. Holes were drilled (about inch) into mason jar lids to accommodate a rubber septum. Prior to conducting respiration experiments, product densities were measured via water displacement in the jars (Table 1). Product densities were used to calc ulate head space gas volume from the difference between container volume and sample volume. Nine Samples of each product (ca. 125 g) we re placed in each jar. For Squash and Zucchini samples, about half was squash and half was zucchini, by weight. Lids were placed firmly on jars and holes were sealed with r ubber septa. Three samples of each product were placed in controlled environmental chambers set at 1, 8, and 15C. Oxygen and carbon dioxide concentrations were measured periodically us ing the headspace analyzer (Pac-Check, Mocon,

PAGE 26

26 Inc., Minneapolis, MN). Samples stored at 15, 8 and 1C were measured about every 2 hours, 4 hours, and 12 hours, respectively. Results and Discussion Headspace Sample headspace data proved to be highly vari able, as seen by relatively large standard deviations in Table 2-1. However, da ta appear to be in desirable ranges. Table 2-1. Headspace data from bagged samples. ItemMeanS.D.MeanS.D.(g/cm3)S.D. Rutabaga8.303.1610.812.221.000.001 Sweet Potato11.175.889.415.340.950.015 Squash15.511.207.511.220.880.008 Squash and Zucchini13.451.388.711.190.900.040 Turnips7.462.6911.322.100.900.012 O2 (%)CO2 (%)DensityMeans and standard deviations for headspace data are from 10 samples. Average density values and standard deviations calculated from 3 samples. Respiration and Package O xygen Transmission Rate Changes in carbon dioxide and oxygen concentra tions with time showed approximately linear or hyperbolic trends. Squash and Zucchini at 15C, Rutabaga at 15 and 8C and Turnips at 15 and 8C showed nonlinear behavior. For oxygen, a hyperbolic decay function was used to fit data using non-linear regression (Equation 2-5): t b ab y y 0 (2-5) Where y is oxygen concentration, t is time and y0, a, and b are coefficients. For carbon dioxide, a hyperbolic function was used to fit da ta using a non-linear re gression (Equation 2-6): t b at y y 0 (2-6)

PAGE 27

27 Where y is carbon dioxide concentration, t is time and y0, a, and b are coefficients. Figure 2-2 shows changes in gas compositions for Rutabaga at 15C. Measured data and fitted curves are shown in Figure 2-6 and fitted curve coefficients are provided in Table 2-2. Figure 2-2. Unsteady state respir ation data for Rutabaga at 15C, % vs time. Figure 2-3. Unsteady state respir ation data for Rutabaga at 15C, cc/g vs time.

PAGE 28

28 Some products could be reas onably approximated as linear for changes in oxygen and carbon dioxide with time. These data were fitted with Equation 2-8. b at y (2-7) Where y is either oxygen or carbon dioxide c oncentration, x is time and a, and b are coefficients. Table 2-2 provides coefficients for a ll products at all temperatures for oxygen. Data fitted with Equation 2-8 are indicate d with the term, Linear in the yo column of Table (2-2). Table 2-2. Oxygen resp iration coefficients Tempyo (0C)cc/gabR2Rutabaga15-1.09162.43051.99850.9895 8-0.73732.07993.65450.9907 1-2.84464.116238.01570.9899 Sweet Potato15-2.70404.03572.12000.9908 8-3.84335.17095.44680.9958 1Linear-0.31741.33130.9958 Squash15-2.68894.00523.70000.9961 8Linear-0.49571.33980.9877 1Linear-0.17331.35360.9839 Squash and Zuchinni15-0.55431.8991.36090.9921 8Linear-0.45891.34030.9952 1Linear-0.15951.34560.9934 Turnips15-1.29612.54583.36360.9708 8-0.74431.95456.57620.9832 1Linear-0.06181.11300.9704 Rates of respiration for both oxygen and carbon dioxide were calculated from the mathematical derivatives of the non-linear regr ession functions. Cases where gas compositions changed linearly with time suggested that re spiration rate was not a strong function of gas composition under the specific test conditions and th ese were considered to be a constant equal to the slope of the fitted curv e. Rates of oxygen consumption were similar to carbon dioxide evolution, suggesting respiration quotients, RQ, of about unity for all products. Therefore, further calculations were base d solely on oxygen consumption. Table (2-3) provides additional

PAGE 29

29 data used to estimate average rates of oxygen c onsumption at apparently desirable package oxygen levels for each product at each temperature. Table 2-3. Required OTR at design temperature and desired O2 level Product weightOTR Design T Desired O2Film Areain packageFilm OTRRequired Item0C(%)(cm2/bag)(g)(cc/day/bag)(cc/day/bag) Rutabaga3.08.0817.484542544 Sweet Potato3.012.0794.2956839232 Squash5.010.0719.7834038100 Squash and Zuchinni5.010.0752.0034038100 Turnips3.07.5785.973402924 The respiration rates were then calculat ed at the desired temperature and oxygen concentration and compared to the OTR of the film at the desired temperature. Table 2-3 indicates that the packages fo r all the products except for turn ips do not have a high enough OTR to meet the respiration requirements at the design temperature and desired O2 level and therefore perforations are necessary. Example of How to Calculate Respir ation Rate from Respiration Data For rutabaga, design temperature is 3C and desired O2 level is 8%. It would be ideal to conduct respiration studies at de sign temperature, but if data are not available they may be inferred from the Arrhenius temperature sensitivity relationship. Oxygen respiration rate at 8% headspace oxygen must be calculated at 1, 8 an d 15C. Then, oxygen respiration rate at 3C may be calculated from the Arrhenius relationship. Using 15C for demonstration, time to reach the desired O2 level may be estimated from the O2% time curve (Figure 2-2). The Figure shows that it takes approximately 1 day to reach 8% O2 at 15C. Time can be substituted into the math ematical derivative of equation (2-6), which is given by 2t b ab dt dy (2-8)

PAGE 30

30 Substituting time and coefficients given in Table 2-2 yields day g cc 54025 0 1 9985 1 9985 1 4305 22 dt dy Following the same procedure for 8 and 1C gives oxygen respiration rates of -0.20067 and -0.07155 cc/g/day, respectively. Arrh enius temperature sensitivity is given by Equation 2-9 T 11047 O38.969 R2 e (2-9) where T is the absolute temperature in Kelvin. Substituting design temperature 276.15 K into Equation 2-9 gives day g cc 09650 0 R2O Multiplying 2OR by the weight of the product in the package from Table 2-3 gives 44 cc/day. An OTR of 44 cc/day is required to maintain a 454 g package of rutabaga at 3C and 8% O2. OTR of commercial package for Rutabaga measured in this experiment is 25 cc/day from Table 2-3.

PAGE 31

31 CHAPTER 3 METHOD FOR MEASURING THE OXYGEN TR ANSMISSION RATE OF PERFORATED FILMS Introduction Few commercially available films have su fficiently high oxygen transmission rates for packaging of respiring products. Many fruits and vegetables, such as st rawberries and mangos have high respiration rates which makes it di fficult to supply sufficient oxygen through packaging films without perforations. Films with perforations on the or der of 40 to 250 m are generally referred to as micro-perforated films. Design of packages using micro-perforated films has been difficult due to lack of methods cap able of properly measuring OTR of films with perforations. OTR of micro-perf orated film depends on temperat ure dependant factors including permeability of the film, perforation geometry, film thickness, and number of perforations in a given area of film. Difficulties measuring OTR of perforated films with traditional approaches is evident. Figure 3-1 shows the coulometric approach that is the basis of instrumentation supplied by Mocon, Inc. (Minneapolis, MN). The figure shows a test where oxygen would permeate from right to left through the sample film mounted in the middle. Test films split the test chamber into two ha lves. An oxygen containing gas (test gas) flows on one side while an oxygen free gas (carrier gas) flows on the other. This system works well for film samples without perfor ations since slight variations of pressure on either side of the sample do not significantly alter measurements. Howe ver, when perforations exist, variations in pressure cause gas to flow freely from one side to the other, which directly affects measurements. It is difficult to imagine how this approach could be designed to work reliably for perforated films.

PAGE 32

32 Figure 3-1. Typical apparatus for m easuring OTR using coulometric method. Figure 3-2 shows an alternative method fo r measuring OTR, which requires headspace sampling over time. Actual experiments often require removal of multiple samples from a single test specimen. Without perforations, each sa mpling changes headspace volume, which affects the measurement. With perforations, each samp le draws new gas into the headspace, changing gas compositions, thus affecting subsequent samples To overcome these difficulties, a new appro ach was developed using a fluorescence based fiber optic sensor that is capable of continuously measuring gas within th e test apparatus without removing or consuming gas and without a need for continuously flowing gases. Theory Attempts to predict transmission rates of gase s through perforated films have been made. Emond et al., (1991) and Fonseca et al., (1996) used empirical mode ls to describe diffusion of gases through perforated films. Fishman et al., (1996) modele d transmission rates of gases using

PAGE 33

33 Ficks law of diffusion, while Hira ta et al., (1996) used Grahams law of diffusion. Renault et al., (1994a) modeled diffusion of gas through perforated films with Maxwell St efans law. Ghosh and Anantheswaran (1998) determined that models based on Ficks law were in closest agreement with experimental data. Figure 3-2. Unsteady state m easurement of headspace over time Oxygen transfer rate of perforated f ilm depends on two mechanisms including permeation of oxygen through the base film a nd diffusion of oxygen through the perforation. Total flow through the film was described by Fishman et al. (1996) as: h hA J JA F (3-1) Where A is the total area of the film, J is the flux of oxygen through the film, Ah is the total area of the holes, and Jh is the flux of gas through a unit area of a hole. Permeation of gas through the film is given by: L ) p (p P J2 1 (3-2) Ai r Film Perforation

PAGE 34

34 Where P is the permeability of the film, L is film thickness, pi is partial pressure of oxygen inside the package and pA is partial pressure of oxygen in the atmosphere surrounding the package. Diffusion of oxygen through perforat ions should obey Ficks Law: h 2 1 hL ) p D(p J (3-3) Where D is the diffusion coefficient of ga s in air through the perforation and Lh is the diffusion path length. If the distance be tween perforations is much gr eater than the radius of the perforation than Lh can be approximated by the model employed by Meidner and Mansfield (1968) and Nobel (1974) fo r stomatal resistance. h hR L L (3-4) Where Rh is the radius of the hole. Combining equati ons (3-1), (3-2), (3-3), and (3-4) yields h h AR L D A L P A p) (p F (3-5) To achieve a stable, steady state gas composition in packaged produce gas transfer must equal respiration rate at the desired gas composition. Unsteady state methods as described by Lee et al., (1991) can be used to determine the respirati on rate at the desired gas composition. Once the respiration rate is known the area of the pack age, the number and size perforations, and the weight of the product can be dete rmined. Setting the respiration ra te of the produc t equal to the gas transmission rate through the film (3-5) yields h h O AR L D A L P A ) p (p wR2in (3-6)

PAGE 35

35 The term h hR L D A L P A is the total OTR of the package a nd (3-6) reduces to the steady state design equation for a modified atmosphere package of fresh produce. perf O A)OTR p (p wR2in (3-7) Oxygen Transmission Rate (OTR) Measurements Non-perforated films Ghosh and Anantheswaran (1998) reviewed four methods used to determine OTR. These methods include (1) manometric (ASTM D 1434, 1995), (2) volume (ASTM D1434, 1995), (3) coulometric sensor method (ASTM D3985, 1995) and (4) concentration increase methods (Landrock and Procter 1952; Moyls et al., 1992). Both manometric and volume methods rely on the same type of apparatus. Neither approach is appropriate for perfor ated films, so these are only briefly described here. A sample is mounted in a gas transmission cell to form a sealed semibarrier between two chambers. One chamber contains test gas at a specific high pres sure, and the other chambe r at a lower pressure receives the permeating gas. In the Manometric method the lower pressure chamber is evacuated and transmission of the gas through the film is indicated by an increase in pressure. In the volume method the lower pressure chamber is main tained at atmospheric pressure and the gas transmission is indicated by a change in volume. The coulometric method Figure 3-1 involves mounting a specimen as a sealed semibarrier between two chambers at atmospheric pressure. One chamber is purged with a nonoxygen containing carrier gas such as nitrogen, and the other chamber is purged with oxygen containing test gas, which is typically air (21% oxygen) or 100% oxygen. Oxygen permeates through the film into the carrier gas, which is th en transported to a coulometric sensor. Oxygen

PAGE 36

36 is consumed in a process that generates an el ectric current proportiona l to the amount of oxygen flowing to the sensor in a given time period. The concentration increase method is an unsteady state method whereby the chamber is sealed with a semi-barrier and is initially pur ged with an oxygen free gas such as nitrogen. Oxygen diffuses through the barrier and the conc entration of oxygen is measured over time. The most common method used to measure the oxygen concentration is a gas chromatograph, which requires removal of gas samples from the test chamber (Figure 3-2). Perforated films The volume and manometric methods invol ve a pressure differential which would cause gas to flow through perforations, rendering thes e methods unsuitable for OTR measurements of perforated films. The coulumetric method has basic physical limitations (Johnson and Demorest 1997) and becomes impractical for very high OTRs even without perforations due to costly sensor consumption. Perforati ons create additional challenges due to practical difficulties of avoiding non-diffusional gas flow through perforations. The approach developed in this work is an enhancement of the typical concentration increase method. This approach is superior to other methods since the measurement does not rapidly consume the sensor, the sensor does not consume gases involved in the measurement, the apparatus does not require consum ption of constantly flowing gases, and the approach does not create or rely upon pressure differentials. Fiber optic oxygen sensor Sensors based on oxygen quenching fluorophores are commercially available. Typically fluorophores are suspended in sol gel complex a nd mounted at the tip of a fiber optic probe. Oxygen probes available from Ocean Optics Inc. (Dunedin, Fl) use a fluorescing ruthenium complex. For durability, probes ma y be mounted in steel shafts of varying diameter in a manner

PAGE 37

37 that resembles hypodermic needles. For this work 18 gauge probes were used (Model FOXY 18G, Ocean Optics Inc, Dunedin, Fl). A pulsed bl ue LED sends light, at 475 nm, onto an optical fiber. The optical fiber carries the light to th e probe tip, which excites the flourophore causing an emission at ~600 nm. Excitation energy is also tr ansferred to oxygen molecu les in non-radiative transfers. Therefore oxygen decreases or quenches the fluorescence signal (Kautsky 1939). Florescent energy is collected by the probe and carri ed through the optical fiber to spectrometer. Degree of fluorescence quenching relates to th e frequency of collis ions, and therefore concentration, pressure and temperature of the oxygen-containing media. A fluorescence quenching based sensor was selected for use in this method primarily because it can measure oxygen concentration without consuming oxygen. Ot her methods require removal of gas from the system or consumption of oxygen, wh ich directly affects the measurement. Materials and Methods The apparatus for measuring OTR was divided into in three parts, which, in this case, were fabricated mainly from magnesium metal, wh ich was readily available in our machine shop (Figure 3-3). The bottom incorporates a transp arent plastic window in order to allow for a magnetic stir bar in the test chamber. The hei ght of the middle section is 5 cm and is a hollow cylinder with four ports for flushing with nitr ogen and compressed air, mounting the fiber optic oxygen probe, and to provide for a gas outlet va lve. The middle also accommodated o-rings for gas tight seals with top and bottom. The t op is a ring with a pr ecise open area of 50 cm2 to accommodate film samples. Figure 3-3 shows a diagram of the OTR measurement chamber.

PAGE 38

38 air probe N2tightening screw O-ring Groove Outlet Stream PlexiGlass PlateMagnetic Stir Bar Figure 3-3. Schematic Profile of OTR chamber Measurement of Samples Stainless steel disks 0.02 inches thick with precision orifices were procured (FSS-318-cal100, 150, 200, 250, Lenox Laser, Glen Arm, MD) a nd used to test the apparatus since we found it difficult to repeatedly produce consistent holes with desired ge ometry in our laboratory. Hole diameters were 100, 153, 205, and 249m. Oxygen pa rtial pressure in the chamber was recorded every 10 seconds using the average of four m easurements with the fiber optic oxygen sensing system. Measurements were made at 150C, 230C, and 300C inside a computer controlled environmental chamber. From the change in oxyge n partial pressure over time, OTR of holes can be determined with the following Ficks law based equation for a well stirred volume (Emond, 1992). V ) p (p OTR dt dp2 2 2O air O perf O (3-8) This can be integrated from initial time 0 to t and from initial partial pressure 0 O2p to 2Opyielding:

PAGE 39

39 t V OTR p p p p lnperf 0 O air O O air O2 2 2 2 (3-9) Recalculating Diffusion Coefficients Diffusion coefficient of oxygen in air was calcu lated from OTR of the precision orifices by setting the term h hR L D A in equation (3-6) equal to OTR and solving for D, which yields h hA R L OTR D (3-10) Values calculated from equation 3-10 were comp ared to the Fuller, Schettler, and Giddings relation from Perrys Chemical Engineeri ng Handbook, (Perry and Green 1984) Table 3-1. Results and Discussion A plot was made from equation (3-9) and th e OTR was calculated by multiplying the slope by the volume of the chamber. An example of this plot is provided in Figure 3-4 for the case of the 249m hole at 30 0C. y = 2.2701x 0.0062 R2 = 0.9993 0 0.05 0.1 0.15 0.2 0.25 0.3 00.020.040.060.080.10.12 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure 3-4. Plot used to determine OTR of hole/perforation 249m hole at 300C.

PAGE 40

40 Figure 3-5 shows OTR data, at least in duplicat e, for all holes at all temperatures. The figure primarily shows that the apparatus is capable of providing consistent and reliable measurements. Additionally, the figure shows a surprising tendency for OTR to decrease with increasing temperature, despite the fact that ga s diffusion coefficients are generally known to increase with temperature. It is likely that reduced gas density at higher temperatures more than offset increases in gas diffusion coefficients 0 100 200 300 400 500 600 700 100153205249 hole diameter (microns)OTR (cc/day) 15 C 23 C 30 C Figure 3-5. OTR of holes vs. temperature Table 3-1. Oxygen diffusion coe fficient in air calculated from precision orifices and Perrys Chemical Engineering Handbook D_O2cm2/s152330 Perry's0.1860.1960.204 100 m0.4530.3740.282 150 m0.3310.2830.304 200 m0.3110.2410.214 250 m0.2570.2340.231 Temperature 0C Table 3-1 shows that the di fference between oxygen diffusion coefficients estimated from Perrys and the precision orifi ce decreases with increasing temperature and with increasing diameter. However, for most modified atmosphere packaging applications, temperatures tend to be low and temperature variations are much less pronounced, reducing the potential value of this observed trend. Most importantly however, OTR measurements with precision holes proved to

PAGE 41

41 be consistent and reproducible. This provides confidence that th is approach can be used to accurately measure OTR in microperforated packag ing films where such microperforations tend to be dimensionally irregular.

PAGE 42

42 CHAPTER 4 NEW APPARATUS SIMPLIFIES DESIGN OF MODIFIED ATMOSPHERE PACKAGING WITH PERFORATED FILMS Introduction In previous chapters respiration rates were measured on five respiring products and a new method was developed to determine the Oxygen Tr ansmission Rate (OTR) of perforated films. In this experiment respiration rates on brocco li were measured using the unsteady state method described in chapter 2. OTR of perforated and non perforated portions of the package were measured. Non-perforated portions of the packag e were measured using the Oxtran 2/20 (Mocon Inc., Minneapolis, MN.) Perforated portions were measured using the method developed in Chapter 3. Perforated packages of broccoli we re designed and gas composition inside packages was measured periodically until each package reached steady state. OTR was calculated from equation (3-7) using measured respiration rates and as well as rates from the literature. Predicted OTR was found to agree well with measured OTR. Materials and Methods Head Space Analysis of Commercially Packaged Broccoli A headspace analyzer (Pack Check, Mocon, Inc., Minneapolis, MN) was used to determine oxygen and carbon dioxide concentrations in sample headspaces of the prepackaged broccoli. Headspace gas composition of 14 bags of commerci ally packaged broccoli was measured. Respiration Rate of Broccoli Product respiration rates were measured usi ng an unsteady-state method (Lee et al., 1991; Hagger et al., 1992). Briefly, a given amount of br occoli was placed in herm etically sealed jars and changes in headspace gas compositions are monitored over time. Empirical curves are fitted to gas versus time data and mathematical deriva tives of these curves (instantaneous slopes), provide respiration rates as a f unction of headspace composition.

PAGE 43

43 One liter mason jars were used for unsteady-state respiration experiments. Holes were drilled (about inch diameter) into mason jar lids to accommodate rubber septa. Prior to conducting respiration experiments, broccoli de nsity was measured via water displacement. Broccoli density was used to calculate head space gas volume from the difference between the container volume and sample volume. Five Samples of broccoli (ca. 100 g) were placed in each jar. Lids were placed firmly on jars and holes and were sealed with rubber septa. Samples of broccoli were placed in a controlled environmental chamber set at 4C. Oxygen and carbon dioxide concentrations were measured periodically using the headspace analyzer (Pac-Check, Mocon, Inc., Minneapolis, MN). Broccoli Package OTR Broccoli packages were made from polyethylene with a thickness of 2.5 mil (Paragon Film Inc. Broken Arrow, OK). Oxygen transmission rates of two non-perforated samples 100 cm2 each were measured using the Oxtran 2/20 (Mocon, Inc., Minneapolis, MN) at 200C and 300C. The Arrhenius Temperature Sensitivity Relati onship was used to determine the OTR at 40C. Total area of the non-perforated region of the package was 1000 cm2. One perforated portion of the package with an area of 50 cm2 was measured using a device employing a fiber optic oxygen sensor as described in chapter 3 at 40C. Modified Atmosphere Package Design with Perforations Ten bags were designed using polyethylene film with a thickn ess of 2.5 mil (Paragon Film Inc. Broken Arrow, OK) and an area of 1050 cm2 (30 cm x 35 cm). Bags were sealed using a heat sealing machine (Sencorp Systems, Inc. Hyannis, MA). Approximately 110 grams 1 gram of broccoli florets were added to each bag. All ba gs were perforated once with a 13.5 gage tool. A headspace analyzer (Pack Check, Mocon, Inc., Minneapolis, MN) was used to determine oxygen and carbon dioxide concentrations in the headspace of the packaged broccoli.

PAGE 44

44 Measurements were made approximately ever y 12 hours until gas compositions reached steady state. Results and Discussion Headspace of Commercially Packaged Broccoli Broccoli was found to have a density of 0.815 g/cm3. Fourteen samples were taken with an average of 5.18 2.41% O2 ranging from 1.32% O2 to 9.06% O2 and 5.86 1.29% CO2 ranging from 8.4% CO2 to 4.1% CO2. Respiration of Broccoli Changes in carbon dioxide and oxygen concentr ations with time for broccoli showed hyperbolic trends. For oxygen, a hyperbolic decay function was used to f it data using non-linear regression (Equation 4-1): t b ab y y 0 (4-1) Where y is oxygen concentration, x is time and y0, a, and b are coefficients. For carbon dioxide, a hyperbolic function was used to fit da ta using a non-linear re gression (Equation 4-2): t b at y y 0 (4-2) Where y is carbon dioxide concentration, x is time and y0, a, and b are coefficients. Figure 2 shows changes in gas compositions for Broccoli at 4C. Measured data and fitted curves are shown in Figures (4-1) and (4-2) and fitted curv e coefficients are provided in Table (4-1).

PAGE 45

45 Figure 4-1. Unsteady state resp iration data for Broccoli at 4C % vs time Figure 4-2. Unsteady state resp iration data for Broccoli at 4C cc/g

PAGE 46

46 Table 4-1. Respiration coefficients for oxygen and carbon dioxide for broccoli y0ab cc/gcc/gdaysR2O2-1.71033.35384.08330.9881 CO20.04902.86005.85230.9789 Broccoli Package OTR Non-perforated portions of the p ackage had an average OTR of 3900 cc/m2/day at 200C and 6600 cc/m2/day at 300C. The Arrhenius temperature sensi tivity relationship equation (4-3) suggests an OTR of about 1500 cc/m2/day at 40C. T 4734 1010 3.99 OTR e (4-3) Non-perforated portion of the package ha d a total oxygen transmission rate of 150 ccO2/day. OTR of the perforated region was 570 cc/ day calculated from measured data as described in Chapter 3 as shown in (Figure 42). The total OTR of the package was 720cc/day. Perforated region accounted for about 80% of OTR de spite having an area slightly less than 5% of the package area. This result is expected sinc e the diffusion coefficient is about six orders of magnitude greater than the permeability coeffici ent in equation (3-5) for polyethylene. When total area of all perforations is large enough compared to total package area the permeation term in equation (3-5) becomes negligible compared to the diffusion term and practically all OTR comes from the perforations. Broccoli Package Performance Data Packages reached an average steady state of 11.6% O2 with a standard deviation of 3.04% O2 ranging from 6.54% O2 to 14.5% O2. Average CO2 concentration was 4.4% CO2 with a standard deviation of 0.684% CO2 ranging from 5.5% CO2 to 3.6% CO2. Figure (4-3) shows broccoli packages reaching steady state.

PAGE 47

47 y = 2.3235x + 0.0255 R2 = 0.9934 -0.2 0 0.2 0.4 0.6 0.8 1 00.10.20.30.4time (days)-ln((pO2a-pO2)/(pO2ai-pO2i)) Figure 4-2. Plot used to determ ine OTR of hole/perforation at 40C. 0 5 10 15 20 25 0.0020.0040.0060.0080.00100.00120.00 time (hour)%O2, %CO2O2CO2 Figure 4-3. Broccoli packages reaching steady state Calculation of Broccoli oxygen consumption rate Broccoli oxygen consumption rate was calculated at average steady state values and storage temperature. Figure 1 show that it takes approximately 1.1 days to reach 11.6% O2 at 4C. Time can be substituted into the mathemati cal derivative of equati on (4-1), which is given by

PAGE 48

48 2t b ab dt dy (4-4) Substituting time and coefficien ts given in Table 4-1 yields day g cc 510 0 1 1 0833 4 0833 4 3538 32 dt dy Multiplying this value by the weight of the pr oduct in the package (110 g) gives a total oxygen consumption rate of 56 cc/day. Prediction of OTR Package using Design Equation Respiration rates calculated from this expe riment using the same method described in Chapter 2 and from the literature (Hagger et al., 1992) were used to estimate actual OTR of the package. Experimental respiration rate at 4C and average steady state concentrations was 0.530 ccO2/g/day and the respiration rate deri ved from the literature was 0.820 ccO2/g/day. Equation 37 suggests OTR values of 630 cc/day and 970 cc/da y using our experimental and literature values respectively. Measured OTR using our ne w apparatus was 720 cc/day, which agreed well with predicted values.

PAGE 49

49 CHAPTER 5 CONCLUSIONS Modified atmosphere packaging is a simple and inexpensive way to extend the shelf life of minimally processed produce. Lower oxygen e nvironments at lower temperatures can significantly reduce the respir ation rate of produc e. Headspace oxygen concentration of packaged produce is dependent on two main f actors: the oxygen tran smission rate of the packaging material and the oxygen consumption by the product due to respiration. Oxygen consumption of the produce at the storage temp erature and desired oxyge n concentration must match the oxygen transmission rate of the packag e to maintain the desired atmosphere. When designing a modified atmosphere package it is necessary to m easure the OTR of the packaging material selected and the resp iration rate of the product. The unsteady state method is an effective way to measure respiration rates at a specified temperature over a range of O2 and CO2 concentrations. A hyperbolic decay function fit many of the products including rutabaga and broccoli indi cating a more dramatic decrease in respiration rates at higher O2 levels. Some products shift from a hyperbolic decay function to a linear function at lower temperatures suggesting that respiration is not a strong function of oxygen concentration at these temperatures. This be havior was observed in sweet potato, squash, zucchini, and turnips. Once respir ation rate has been measured at the specified conditions, OTR necessary to maintain desired O2 level can be calculate d from equation (3-7). Most of the oxygen consumpti on rates of products measured in this work at the recommended temperature and O2 level exceeds the oxygen transmission rate of commercially available packaging material. Perforations in th e package are necessary to maintain the desired O2 level at the storage temperature. Currently the methods commonly used to measure OTR of packaging material have deficiencies that make them unsuitable for measuring OTR of

PAGE 50

50 perforated packages. A new apparatus was deve loped to overcome these deficiencies. This method is a variation of the con centration increase method and i nvolves the use of a fiber optic oxygen sensor to measure oxygen concentration over time. From oxygen concentration data OTR can be calculated. The new apparatus was us ed to measure OTR of four calibrated holes with diameters of 100, 153, 205, and 249 m, each hole measured at 15, 23, and 30C. OTR increased with increasing diameter and decrea sed with increasing temperature which was not expected. Decreased OTR with increasing temper ature could be due to decreasing gas density offsetting increase in diffusion coefficients. This trend is not important fo r modified atmosphere packaging applications which occur at lower te mperatures with less te mperature variation. Consistent and reproducible measurements with precision orifices provide confidence that the apparatus can be used to measure OTR of micro-perforated films. A modified atmosphere package was desi gned for broccoli using the new apparatus. Broccoli respiration rates were measured usi ng the unsteady state met hod at 4C, the optimal storage temperature for broccoli. Perforated packag es were designed for broccoli. Packages were perforated with a 13.5 gage tool. Package OTR c onsisted of two parts a perforated portion and a non perforated portion. Non-perf orated OTR was measured using the Oxtran 2/20 (Mocon Inc., Minneapolis, MN) at 20C and 30C. Arrhenius temp erature sensitivity relationship was used to infer OTR at 4C. Perforated OTR was measured using the new apparatus. Total OTR was calculated by adding non-perforated OTR to pe rforated OTR. Perforated OTR accounted for 80% of total OTR despite having an area twenty times less than the nonperforated region. Packaged broccoli was then stored at 4C and headspace composition was allowed to reach steady state. OTR necessary to maintain the average steady state O2 level was calculated using both measured respiration rate and respiration rate from the literature and compared. Both

PAGE 51

51 calculated OTRs were the same order of magnit ude and measured OTR was in between the two. This suggests the new apparatus is a useful tool for designing a modified atmosphere package for respiring produce.

PAGE 52

52 APPENDIX A RESPIRATION DATA FOR THE FIVE RESPIRING PRODUCTS Table A-1. Rutabaga respiration data 15C time (hours)time (days)%O2% CO2 ccO2/gccCO2/g 0.000.0021.0 0.0 1.330.00 0.000.0021.0 0.0 1.300.00 0.000.0021.0 0.0 1.310.00 0.720.0320.6 1.1 1.300.07 0.730.0320.7 1.1 1.290.07 0.750.0320.6 1.3 1.290.08 2.680.1119.7 2.4 1.240.15 2.680.1119.7 2.3 1.220.14 2.700.1119.1 3.0 1.190.19 4.400.1818.4 3.7 1.160.23 4.420.1818.7 3.4 1.160.21 4.430.1817.8 4.3 1.110.27 6.000.2517.4 4.7 1.100.30 6.000.2517.7 4.4 1.100.27 6.020.2516.6 5.6 1.040.35 7.750.3216.6 5.8 1.050.37 7.770.3216.8 5.1 1.040.32 7.780.3215.6 6.8 0.980.43 9.030.3815.6 6.0 0.990.38 9.050.3816.0 5.6 0.990.35 9.070.3814.6 6.9 0.910.43 10.580.4414.7 6.7 0.930.42 10.580.4415.2 6.4 0.940.40 10.600.4413.5 7.8 0.840.49 17.370.7211.6 8.9 0.720.55 17.380.729.89 10.3 0.620.64 20.370.8510.1 9.9 0.640.63 20.420.8510.2 9.9 0.630.61 20.430.858.95 11.2 0.560.70 22.820.959.26 10.6 0.580.67 22.820.959.28 10.6 0.580.66 22.830.957.54 12.0 0.470.75 25.521.068.22 11.4 0.520.72 25.521.068.2411.3 0.510.70 25.531.066.61 12.8 0.410.80 26.831.127.83 11.8 0.490.73 26.871.126.42 13.1 0.400.82 29.901.257.21 12.2 0.450.76 29.921.255.43 13.6 0.340.85 34.821.455.36 13.4 0.330.83 35.821.495.98 13.1 0.380.83 37.451.564.70 13.8 0.290.86 37.471.563.13 15.0 0.200.94 46.001.922.79 16.1 0.171.00 46.021.923.23 15.0 0.200.95 46.021.921.86 17.1 0.121.07 51.182.131.74 16.4 0.111.02 51.232.131.04 18.1 0.071.13 53.072.212.2 16.8 0.141.06 54.272.260.358 18.2 0.021.15 60.282.510.276 17.5 0.021.09

PAGE 53

53 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.002.503.00 time (days)% CO2, O2 %O2 %CO2 Figure A-1. Rutabaga 15C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.000.501.001.502.002.503.0 0 time dayscc/g ccO2/g ccCO2/g Figure A-2. Rutabaga 15C, cc/g vs time

PAGE 54

54 Table A-2. Rutabaga respiration data 8C times (hours)times (days)%O2% CO2 ccO2/gccCO2/g 0.000.0021.00.01.310.00 0.000.0021.00.01.310.00 0.000.0021.00.01.320.00 4.000.1719.82.11.230.13 4.000.1720.31.71.260.11 4.020.1720.01.91.260.12 7.520.3119.22.81.190.17 7.570.3218.83.31.170.21 7.570.3219.03.01.200.19 9.300.3918.93.11.180.19 9.320.3918.13.91.130.24 9.330.3918.53.51.160.22 17.720.7415.75.60.980.35 17.720.7416.84.71.040.29 17.730.7416.35.41.030.34 20.820.8714.76.50.910.40 20.830.8715.95.80.990.36 20.850.8715.55.90.980.37 30.201.2612.38.40.760.52 30.201.2614.07.10.870.44 30.221.2613.37.60.840.48 37.731.5710.59.60.650.60 37.731.5712.48.00.770.50 37.751.5711.68.70.730.55 46.321.939.210.50.570.65 46.321.9310.98.90.680.55 46.331.9310.09.90.630.62 54.552.277.9311.10.490.69 54.552.275.612.700.350.79 54.582.277.0912.40.450.78 72.933.046.8612.00.430.75 72.933.046.2410.300.390.64 72.953.045.7713.00.360.82 81.003.383.514.200.220.88 81.023.384.5713.80.290.87 81.053.386.1812.60.380.78 115.834.832.1515.10.130.94 115.884.835.6213.000.350.81 115.924.832.8914.70.180.93 121.235.051.8415.30.120.96 162.656.780.58116.60.041.03 162.656.782.4015.000.150.93 162.676.780.13916.90.011.06

PAGE 55

55 0.0 5.0 10.0 15.0 20.0 25.0 0.001.002.003.004.005.006.007.008.00 time (days)% CO2, O2 %O2 %CO2 Figure A-3. Rutabaga 8C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.001.002.003.004.005.006.007.008.00 time dayscc/g ccO2/g ccCO2/g Figure A-4. Rutabaga 8C cc/g vs time

PAGE 56

56 Table A-3. Rutabaga respiration data 1C times (hours)times (days)%O2% CO2 ccO2/gccCO2/g 0.000.0021.00.01.330.00 0.000.0021.00.01.300.00 0.000.0021.00.01.320.00 11.170.4719.72.31.240.15 11.200.4719.82.11.230.13 11.220.4719.91.91.250.12 30.551.2717.94.01.130.25 30.551.2718.13.81.120.24 30.571.2718.43.51.150.22 46.731.9516.75.21.050.33 46.731.9516.45.11.020.32 46.751.9516.74.71.050.29 66.952.7915.16.60.950.42 66.952.7915.06.20.930.39 66.982.7915.06.00.940.38 92.223.8413.58.00.850.51 92.223.8413.18.10.810.50 92.233.8413.27.40.830.46 138.975.7912.39.10.780.57 138.985.7911.98.20.750.51 163.986.8310.59.30.650.58 164.006.8311.010.10.690.64 164.026.8310.79.30.670.58 189.887.919.1010.20.570.63 189.907.919.6811.60.610.73 189.907.919.1910.00.580.63 216.939.048.4912.50.540.79 216.979.047.7011.00.480.68 216.989.047.7311.00.480.69 240.2310.016.4311.70.400.73 240.2510.017.4513.40.470.85 240.2510.016.9211.50.430.72 258.2010.766.6514.20.420.90 258.2010.765.3812.30.330.76 258.2210.765.5312.30.350.77 286.5811.945.3415.50.340.98 286.6211.944.0013.20.250.83 286.7211.954.1013.30.250.83 380.6815.860.55418.80.031.19 380.7215.860.59117.30.041.07 380.7715.870.48916.90.031.06

PAGE 57

57 0.0 5.0 10.0 15.0 20.0 25.0 0.005.0010.0015.0020.00 time (days)% CO2, O2 %O2 %CO2 Figure A-5. Rutabaga 1C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.005.0010.0015.0020.00 time dayscc/g ccO2/g ccCO2/g Figure A-6. Rutabaga 1C, cc/g vs time

PAGE 58

58 Table A-4. Sweet Potato respiration data 15C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 2.280.1019.23.11.190.19 2.280.1019.43.01.200.19 2.320.1018.64.01.150.25 4.370.1817.05.61.050.35 4.370.1817.35.41.070.33 4.380.1816.07.20.990.45 6.830.2814.28.80.880.54 6.830.2814.88.40.920.52 6.870.2912.910.90.800.68 9.000.3811.811.60.730.72 9.000.3812.510.90.770.67 9.030.3810.114.10.630.87 12.070.509.3814.50.580.90 12.070.508.4615.40.520.95 12.100.506.6818.40.411.14 13.800.576.7517.10.421.06 13.800.577.7015.30.480.95 13.830.585.0120.70.311.28 21.330.892.0923.60.131.46 21.330.891.4724.60.091.52 21.370.890.39128.30.021.76 23.850.991.0225.90.061.60 23.850.990.59526.90.041.66 25.821.080.4627.20.031.68

PAGE 59

59 0.0 5.0 10.0 15.0 20.0 25.0 30.0 0.000.200.400.600.801.001.20 time (days)%O2, %CO 2 %O2 %CO2 Figure A-7. Sweet Potato 15C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 0.000.200.400.600.801.001.20 time (days)cc/g ccO2/g ccCO2/g Figure A-8. Sweet Potato 15C, cc/g vs time

PAGE 60

60 Table A-5. Sweet Potato respiration data 8C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 4.820.2019.13.11.180.19 4.830.2018.63.71.150.23 4.830.2018.83.51.170.22 9.450.3916.45.81.010.36 9.470.3915.76.80.970.42 9.480.4016.26.41.010.40 12.550.5214.77.50.910.46 12.580.5213.78.80.850.54 12.580.5214.48.40.890.52 21.830.919.6212.40.590.77 21.850.918.0414.70.500.91 21.870.919.2813.50.580.84 26.651.117.0515.00.440.93 26.671.115.3817.70.331.09 26.671.116.7516.30.421.01 31.271.304.8217.50.301.08 31.281.302.9120.90.181.29 31.301.304.6418.90.291.17 45.271.890.38522.40.021.38 45.281.890.40723.80.031.48

PAGE 61

61 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.00 time (days)%O2, %CO 2 %O2 %CO2 Figure A-9. Sweet Potato 8C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 0.000.501.001.502.00 time (days)cc/g ccO2/g ccCO2/g Figure A-10. Sweet Potato 8C, cc/g vs time

PAGE 62

62 Table A-6. Sweet Potato respiration data 1C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 0.000.0021.00.01.300.00 9.880.4119.52.41.210.15 9.900.4119.32.61.200.16 9.900.4119.22.71.190.17 24.531.0217.14.81.060.30 24.551.0216.35.51.010.34 24.551.0217.24.91.070.30 45.681.9012.98.80.800.54 45.701.9011.89.80.730.61 45.701.9011.89.90.730.61 68.402.857.7013.50.480.84 68.422.856.6814.40.410.89 68.422.856.7514.50.420.90 79.383.315.1216.00.320.99 79.403.313.8217.00.241.05 79.403.313.7917.30.241.07 94.683.951.8318.90.111.17 94.703.951.4419.90.091.23 94.703.951.1719.80.071.23

PAGE 63

63 0.0 5.0 10.0 15.0 20.0 25.0 0.001.002.003.004.005.00 time (days)%O2, %CO 2 %O2 %CO2 Figure A-11. Sweet Potato 1C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.001.002.003.004.005.00 time (days)cc/g ccO2/g ccCO2/g Figure A-12. Sweet Potato 1C, cc/g vs time

PAGE 64

64 Table A-7. Squash respiration data 15C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.280.00 0.000.0021.00.01.280.00 0.000.0021.00.01.290.00 2.230.0920.31.61.240.10 2.230.0920.21.81.240.11 2.250.0920.51.51.250.09 4.330.1818.83.01.150.18 4.350.1819.32.71.180.16 4.350.1819.32.61.180.16 6.780.2817.14.71.050.29 6.780.2818.04.11.100.25 6.800.2818.24.01.110.24 8.970.3715.66.30.960.39 8.970.3717.54.81.070.29 8.970.3717.25.21.050.32 12.020.5013.88.10.850.50 12.020.5016.06.40.980.39 12.020.5016.36.40.990.39 13.780.5712.79.20.780.56 13.780.5715.57.20.950.44 13.780.5715.97.10.970.43 21.280.898.713.30.540.82 21.300.8914.09.70.850.59 21.300.8914.79.10.900.56 25.781.076.3015.00.390.92 25.801.0813.410.20.820.62 25.801.0814.210.10.870.62 30.901.293.9417.90.241.10 30.901.2913.810.60.840.65 44.921.870.099221.50.011.32 44.921.8712.112.20.740.74 44.921.8713.7011.20.840.68 53.082.2111.812.80.720.78

PAGE 65

65 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.002.50 time (days)%O2, %CO2 %O2 %CO2 Figure A-13. Squash 15C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.000.501.001.502.002.50 time (days)cc/g ccO2/g ccCO2/g Figure A-14. Squash 15C, cc/g vs time

PAGE 66

66 Table A-8. Squash respiration data 8C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 4.750.2020.21.61.240.10 4.750.2020.21.51.240.09 4.770.2020.41.61.250.10 9.400.3919.02.81.170.17 9.400.3919.02.61.160.16 9.420.3918.72.91.150.18 12.430.5218.33.61.120.22 12.450.5217.93.71.100.23 12.530.5217.93.71.100.23 21.750.9116.05.60.980.34 21.770.9115.55.80.950.36 21.780.9115.06.40.920.39 26.571.1114.77.00.900.43 26.571.1113.77.40.840.45 26.581.1113.28.10.810.50 31.201.3013.57.40.830.45 31.221.3012.08.00.740.49 31.251.3011.58.70.710.53 45.221.886.113.50.370.83 45.221.889.1010.60.560.65 45.231.885.6112.80.340.78 53.372.221.816.10.110.99 53.372.226.2613.10.380.80 53.382.222.4917.50.151.07 67.882.832.43E-0220.90.001.28 67.882.830.70618.30.041.12 67.902.833.32E-0220.10.001.23

PAGE 67

67 0.0 5.0 10.0 15.0 20.0 25.0 30.0 0.000.501.001.502.002.503.00 time (days)%O2,CO2 %O2 %CO2 Figure A-15. Squash 8C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 0.000.501.001.502.002.503.00 time (days)cc/g ccO2/g ccCO2/g Figure A-16. Squash 8C, cc/g vs time

PAGE 68

68 Table A-9. Squash respiration data 1C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 9.830.4120.31.41.240.09 9.830.4120.31.31.240.08 9.830.4120.41.31.250.08 24.421.0219.12.71.170.17 24.421.0219.12.51.170.15 24.431.0219.02.51.170.15 45.651.9017.14.31.050.26 45.651.9017.34.21.060.26 45.651.9017.64.01.080.25 68.352.8515.25.50.930.34 68.352.8515.65.80.960.36 68.352.8514.56.50.890.40 79.333.3113.76.70.840.41 79.333.3114.36.70.880.41 79.333.3112.88.10.780.50 94.603.9411.59.00.700.55 94.603.9412.48.60.760.53 94.603.9410.210.20.630.63 126.625.287.811.20.480.69 126.625.286.311.50.380.70 126.655.283.715.10.220.93 166.836.950.056916.60.001.02 166.856.951.017.60.061.08 166.856.950.026619.60.001.20

PAGE 69

69 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.002.503.00 time (days)%O2,CO2 %O2 %CO2 Figure A-17. Squash 1C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.000.501.001.502.002.503.00 time (days)cc/g ccO2/g ccCO2/g Figure A-18. Squash 1C, cc/g vs time

PAGE 70

70 Table A-10. Squash and Zu cchini respiration data 15C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 0.000.0021.00.01.300.00 2.250.0920.11.71.240.10 2.250.0920.11.61.240.10 2.270.0920.11.61.230.10 4.330.1818.82.91.160.18 4.350.1818.73.01.150.18 4.350.1818.82.91.150.18 6.800.2816.75.11.030.31 6.800.2817.34.61.070.28 6.820.2817.34.61.060.28 8.980.3714.86.90.910.42 8.980.3715.76.30.970.39 9.000.3815.76.30.960.39 12.000.5013.88.30.850.51 12.020.5013.88.30.850.51 12.020.5012.38.60.760.53 13.780.5710.79.70.660.60 13.800.5812.79.40.780.58 13.820.5812.79.40.780.58 21.320.894.9216.20.301.00 21.430.898.913.70.550.85 21.450.898.8813.70.540.84 25.801.071.8018.00.111.11 25.821.087.615.50.470.96 25.831.087.6215.50.470.95 30.721.286.217.10.391.06 30.731.286.2417.10.381.05 30.901.290.420.10.021.24 44.901.874.119.70.251.22 44.921.874.0919.70.251.21 67.822.831.6423.90.101.48 67.832.831.6423.90.101.46

PAGE 71

71 0.0 5.0 10.0 15.0 20.0 25.0 30.0 0.000.501.001.502.002.503.00 time (days)%O2,CO2 %O2 %CO2 Figure A-19. Squash and Zuchini 15C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 0.000.501.001.502.002.503.00 time (days)cc/g ccO2/g ccCO2/g Figure A-20. Squash and Zuchini 15C, cc/g vs time

PAGE 72

72 Table A-11. Squash and Zu cchini respiration data 8C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.280.00 0.000.0021.00.01.290.00 0.000.0021.00.01.300.00 4.800.2020.11.61.230.10 4.800.2020.21.51.250.09 4.820.2020.21.51.240.09 9.450.3918.92.81.150.17 9.450.3919.02.71.180.17 9.470.3919.12.61.170.16 12.520.5218.53.31.150.20 12.530.5218.13.61.110.22 21.820.9115.46.00.940.37 21.820.9115.75.70.970.35 21.830.9116.75.21.020.32 26.631.1118.87.51.150.46 26.651.1114.46.50.890.40 26.671.1115.66.20.960.38 31.251.3012.38.90.750.54 31.251.3012.88.50.790.53 31.271.3014.97.20.910.44 45.271.897.6111.20.460.68 45.271.898.0211.30.500.70 45.281.8912.709.60.780.59 53.282.2211.8010.20.720.63 53.272.223.2421.40.201.32 53.452.234.8414.60.300.89 67.922.830.12518.30.011.12 67.932.830.0418.90.001.17 67.952.8310.2012.80.630.79

PAGE 73

73 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.002.503.00 time (days)%O2,CO2 %O2 %CO2 Figure A-21. Squash and Zuchini 8C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.000.501.001.502.002.503.00 time (days)cc/g ccO2/g ccCO2/g Figure A-22. Squash and Zuchini 8C, cc/g vs time

PAGE 74

74 Table A-12. Squash and Zu cchini respiration data 1C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.300.00 0.000.0021.00.01.290.00 0.000.0021.00.01.290.00 9.850.4120.41.31.260.08 9.870.4120.41.41.260.09 9.870.4120.61.21.260.07 24.471.0219.22.41.180.15 24.471.0219.32.41.190.15 24.481.0220.31.61.240.10 45.671.9017.54.11.080.25 45.671.9017.64.01.090.25 45.681.9019.72.51.210.15 68.372.8515.65.60.960.35 68.372.8515.55.70.950.35 68.382.8518.83.51.150.21 79.353.3114.46.90.890.43 79.353.3114.07.10.860.44 79.373.3118.44.01.130.24 94.633.9412.78.30.780.51 94.653.9412.18.70.740.54 94.673.9418.04.61.100.28 126.635.288.411.50.520.71 126.675.286.912.50.430.77 126.685.2816.56.21.010.38 166.876.951.714.90.100.92 166.876.950.070416.70.001.03

PAGE 75

75 0.0 5.0 10.0 15.0 20.0 25.0 0.002.004.006.008.00 time (days)%O2,CO2 %O2 %CO2 Figure A-23. Squash and Zuchini 1C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.002.004.006.008.00 time (days)cc/g ccO2/g ccCO2/g Figure A-24. Squash and Zuchini 1C, cc/g vs time

PAGE 76

76 Table A-13. Turnip respiration data 15C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.250.00 0.000.0021.00.01.250.00 0.000.0021.00.01.250.00 7.770.3217.54.41.040.26 7.770.3216.65.50.990.33 7.780.3217.54.41.040.26 17.430.7314.27.40.850.44 17.430.7312.69.00.750.53 17.450.7313.68.10.810.48 20.530.8613.18.40.780.50 20.530.8611.59.30.680.55 20.570.8612.58.50.740.50 22.920.9512.48.20.740.49 22.920.9510.610.90.630.65 22.930.9611.79.80.690.58 26.881.1211.209.30.670.55 26.881.129.1511.00.540.65 26.901.1210.911.00.650.65 29.931.2510.509.70.630.58 29.931.258.2511.80.490.70 29.951.2511.011.50.650.68 34.781.459.1910.70.550.64 34.781.456.7412.60.400.75 34.821.458.1811.80.490.70 37.431.568.5910.90.510.65 37.431.565.9813.20.350.78 37.471.567.5111.90.450.71 45.981.926.4412.40.380.74 45.981.923.5314.70.210.87 46.071.925.4113.40.320.80 51.202.135.7012.90.340.77 51.202.132.4315.30.140.91 51.222.134.0915.10.240.90 66.252.763.1315.60.190.93 66.252.760.67214.20.040.84 66.282.761.4815.90.090.94 70.032.922.1015.20.130.91 70.032.921.0216.40.060.97

PAGE 77

77 0.0 5.0 10.0 15.0 20.0 25.0 0.000.501.001.502.002.503.003.50 time (days)% O2, CO2 %O2 %CO2 Figure A-25. Turnips 15C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.000.501.001.502.002.503.003.50 time (days)cc/g ccO2/g ccCO2/g Figure A-26. Turnips 15C, cc/g vs time

PAGE 78

78 Table A-14. Turnip respiration data 8C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.210.00 0.000.0021.00.01.230.00 0.000.0021.00.01.210.00 20.880.8717.14.50.990.26 20.920.8716.64.90.970.29 20.980.8716.65.00.960.29 30.671.2816.05.40.930.31 30.681.2815.26.30.890.37 30.681.2815.36.10.880.35 37.781.5714.86.60.860.38 37.801.5814.16.80.820.40 37.801.5814.07.00.810.40 46.351.9313.86.80.800.39 46.371.9312.97.60.750.44 46.371.9312.97.60.740.44 66.622.7811.58.60.660.50 66.632.7810.39.40.600.55 66.652.7810.39.70.590.56 72.933.0410.810.10.620.58 72.953.0411.410.70.670.63 72.953.049.5510.20.550.59 81.003.3810.09.60.580.56 81.023.388.8210.40.520.61 81.073.388.6910.70.500.62 91.883.839.0410.30.520.60 91.903.837.7111.10.450.65 91.923.837.6411.30.440.65 97.234.058.5510.50.490.61 97.234.057.1311.60.410.67 97.254.057.2011.40.420.67 138.635.787.1911.50.420.66 138.675.785.6212.40.330.72 138.675.785.6012.60.320.73 163.636.825.3612.70.310.73 163.656.823.3413.70.200.80 189.057.883.6213.60.210.79 189.057.881.7414.80.100.86 189.087.882.0414.70.120.85 215.909.000.44516.50.030.95 215.929.000.26015.90.020.93 215.959.001.6015.10.090.87

PAGE 79

79 0.0 5.0 10.0 15.0 20.0 25.0 0.002.004.006.008.0010.00 time (days)% O2, CO2 %O2 %CO2 Figure A-27. Turnips 8C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.002.004.006.008.0010.00 time (days)cc/g ccO2/g ccCO2/g Figure A-28. Turnips 8C, cc/g vs time

PAGE 80

80 Table A-15. Turnip respiration data 1C Time (hours)Time (days)%O2% CO2ccO2/gccCO2/g 0.000.0021.00.01.180.00 0.000.0021.00.01.180.00 0.000.0021.00.01.190.00 30.581.2718.63.11.050.17 30.601.2818.52.91.040.16 30.601.2818.33.31.040.19 46.771.9517.54.00.990.23 46.801.9517.34.10.970.23 46.801.9517.14.40.970.25 67.022.7916.35.10.920.29 67.032.7916.35.00.920.28 67.032.7915.85.30.900.30 92.233.8415.15.90.850.33 92.233.8414.36.50.810.37 92.253.8414.95.90.840.33 139.005.7914.06.60.790.37 139.025.7913.87.30.780.41 139.025.7912.97.40.730.42 164.026.8312.77.60.720.43 164.036.8312.67.60.710.43 164.036.8311.58.60.650.49 189.937.9111.48.50.640.48 189.957.9111.48.50.640.48 189.957.919.929.60.560.54 216.029.0010.29.10.570.51 216.039.0010.29.00.570.51 216.039.008.4910.30.480.58 240.2810.019.069.70.510.55 240.3010.019.629.50.540.53 240.3010.017.4011.00.420.62 258.2510.768.4410.50.480.59 258.2710.768.6110.30.480.58 258.2710.766.3411.90.360.67 286.6011.947.611.10.430.63 286.6211.947.9110.80.440.61 286.6311.944.8812.70.280.72 380.7315.862.4914.10.140.79 380.7515.863.7813.30.210.75 380.7515.860.52215.90.030.90

PAGE 81

81 0.0 5.0 10.0 15.0 20.0 25.0 0.005.0010.0015.0020.00 time (days)% O2, CO2 %O2 %CO2 Figure A-29. Turnips 1C, % vs time 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 0.005.0010.0015.0020.00 time (days)cc/g ccO2/g ccCO2/g Figure A-30. Turnips 1C, cc/g vs time

PAGE 82

82 APPENDIX B OXYGEN TRANSMISSION RATE OF PRECISION ORIFICES Table B-1. OTR of precision orifices at 15, 23, and 30C diameter ( m)15 0C23 0C30 0C 100308254192 153417357384 205581450400 249618564556 OTR (cc/day) y = 1.2571x 0.0121 R2 = 0.9972 -0.05 0 0.05 0.1 0.15 0.2 0.25 00.050.10.150.2 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-1. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 15C y = 1.703x 0.0072 R2 = 0.9997 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 00.10.20.30.40.50.6 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-2. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 15C

PAGE 83

83 y = 2.3698x + 0.0051 R2 = 0.9994 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 00.050.10.150.2time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-3. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 15C y = 2.5236x 0.0024 R2 = 0.9994 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 00.020.040.060.080.10.120.14 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-4. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 15C

PAGE 84

84 y = 1.0371x 0.0083 R2 = 0.9962 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 00.020.040.060.080.10.12time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-5. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 23C y = 1.4554x 0.0063 R2 = 0.9968 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 00.020.040.060.080.10.12 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-6. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 23C

PAGE 85

85 y = 1.837x + 0.005 R2 = 0.9992 0 0.05 0.1 0.15 0.2 0.25 00.020.040.060.080.10.12 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-7. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 23C y = 2.3007x + 0.0007 R2 = 0.9996 0 0.05 0.1 0.15 0.2 0.25 0.3 00.020.040.060.080.10.12time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-8. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 23C

PAGE 86

86 y = 0.7837x 0.0137 R2 = 0.9992 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 00.020.040.060.080.10.120.14time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-9. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 100 m 30C y = 1.5662x 0.0407 R2 = 0.9955 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 00.050.10.150.2 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-10. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 153 m 30C

PAGE 87

87 y = 1.6342x 0.006 R2 = 0.9975 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 00.020.040.060.080.10.12 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-11. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 205 m 30C y = 2.2701x 0.0062 R2 = 0.9993 0 0.05 0.1 0.15 0.2 0.25 0.3 00.020.040.060.080.10.12 time (days)-ln((pO2a-pO2)/(pO2a-pO2i)) Figure B-7. -ln((pO2a-pO2)/(pO2a-pO2i)) vs time 249 m 30C

PAGE 88

88 APPENDIX C BROCCOLI PACKAGE DATA Table C-1 Commercially Packaged Broccoli Head Space Samples Sample Number%O2%CO2 16.074.9 21.498.4 33.265.9 45.77.5 58.744.4 69.064.4 76.784.6 85.155.6 92.446.4 104.66.37 111.327.5 123.636.7 137.585.2 146.714.1 Average5.185.86 Standard Deviation2.421.29 Sample Head Space

PAGE 89

89 Table C-2. Broccoli Respiration Data Time (hours)Time (days)%O2%CO2ccO2/gccCO2/g 0.000.0020.901.620.00 0.000.0020.901.640.00 0.000.0020.901.670.00 0.000.0020.901.660.00 3.200.1319.51.81.530.14 3.220.1319.71.51.520.12 3.220.1319.71.61.570.13 3.220.1319.51.71.550.14 6.370.2718.22.51.410.19 6.370.2718.12.81.420.22 6.380.2718.32.51.460.20 6.380.27182.51.430.20 14.930.6215.44.31.190.33 14.930.62154.51.180.35 14.970.6215.64.61.250.37 14.970.6214.64.31.160.34 24.821.0313.15.81.010.45 24.821.0312.56.70.980.53 24.831.0311.26.20.890.49 24.871.04126.30.960.50 37.821.5810.57.40.810.57 37.821.589.497.80.740.61 37.831.588.698.10.690.65 37.831.587.798.70.620.69 49.722.078.009.00.620.70 49.722.076.849.00.540.71 49.732.076.0410.60.480.85 64.982.715.4510.80.420.83 64.982.713.9812.40.310.97 65.002.712.9812.60.241.01 65.032.711.9213.50.151.07 73.103.054.9411.40.380.88 73.103.052.6313.20.211.03 73.123.051.4713.60.121.09 80.283.350.59614.30.051.14 87.973.671.6914.30.131.11 87.973.670.25315.10.021.18 87.983.670.00042715.80.001.26 100.034.170.00035415.50.001.20

PAGE 90

90 REFERENCES Emond, J.P. 1992. Mathematical modeling of gas c oncentration profiles in perforation-generated modified atmosphere bulk packaging. Ph .D. Thesis, University of Florida. Emond, J.P., Castaigne, F., Toupin, C.J. and De silets, D. 1991.Mathematical modeling of gas exchange in modified atmosphere packaging. Trans. ASAE. 34(1), 239-245. Fishman, S., Rodov, V. and Ben-Yehoshua, S. 1996. Mathematical model for perforation effect on oxygen and water vapor dynamics in modified atmosphere packages. Journal of Food Science 61(5), 956-961 Fonseca, S.C., Oliviera, F.A.R. and Chau, K. V. 1996. Oxygen and carbon dioxide exchange through a perforation, for development of perf orated modified atmosphere bulk packages. Poster presented at Ann. Mtg., June 22-26, Institute of Food Technologists, New Orleans, LA. Ghosh, V. and Anantheswaran, R.C. 2001. Oxyge n Transmission Rate through Micro-Perforated Films: Measurement and Model Comparison. J. Food Process Engineering. 24. Gorny, J.R. 1997. A summary of CA and MA requirements and recommendations for fresh-cut (minimally processed) fruits and vegetables. Vol 5, Fresh-cut Fruits and Vegetables and MAP. J. Gorny (ed) Davis CA, pp. 30-67. Hagger P.E., D.S. Lee, K.L Yam 1992. Application of an Enzyme Kinetics Based Respiration Model to Closed System Ex periments For Fresh Produce Journal of Food Process Engineering 15, 143-157. Hardenburg, R.E., A.E. Watada and C.Y. Wang. 1986. The Comm ercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. USDA Agric. Hdbk No. 66, Washington, DC. Hayakawa, K., Y.S. Henig and S.G. Gilbert. 197 5. Formulae for Predicting Gas Exchange of Fresh Produce in Polymeric Film Package. Journal of Food Science. 40: 186. Henig, Y. S., and Gilbert, S. G., 1975. Computer Analysis of the Variables Affecting Respiration and Quality of Produce Packaged in Polymeri c Films. Journal of Food Science Vol. 40, No. 5, 1033-1035 Hirata, T., Makino, Y., Ishikawa, Y., Katusara, S. and Hasegawa. 1996. A theoretical model for designing a modified atmosphere packaging with a perforation. Trans. ASAE. 39(4), 14991504. Johnson, B. and Demorest, R. 1997. Te sting, permeation and leakage. In The Wiley Encyclopedia of Packaging, (A. Brody and K. Marsh, eds.) pp. 895-901, John Wiley & Sons, New York. Kautsky, H. (1939) Quenching of luminescence by oxygen. Trans. Faraday Soc., 35, 216-219.

PAGE 91

91 Kader, A. A. 1986. Biochemical and physiological ba sis for effects of contro lled and modified atmosphere packaging on fruits and vegetables. Food Technol. 34(3):51-54 Kader, A. A., Zagory, D., and Kerbel, E. L. 1989. Modified atmosphere packaging of fruits and vegetables. Crit. Rev. Food Sci. 28(1): 1-30. Landrock, A.H. and Procter, B.E. 1952. Th e simultaneous measurement of oxygen and carbon dioxide permeabilities of packag ing materials. Tappi. 35(6), 241-246 Laties, G.G. 1978. The development and control of respiratory pathways in slices of plant storage organs. 1978. In Biochemistry of Wounded Plant Tissues, Ed. G. Kahl (ed.), pp. 421-466. Berlin: Walter de Gruyter. Lee D.S., P.E. Hagger, J. Lee, and K.L. Yam 1991. Model for Fresh Pro duce Respiration in Modified Atmosphere Based on Principle of Enzyme Kinetics Journal of Food Science Vol. 56 No. 6, 1580-1585. Leshuk, J.A. and M.E. Saltveit. 1990. Controlled atmospheres and modified atmospheres for the preservation of vegetables. In: M. Ca lderon (ed) Food Preservation by Modified Atmospheres, pp. 315-352 Mannapperuma, J.D., Zagory, D., Singh R. P., and Kader, A. A. 1989. Design of polymeric packages for storage of fresh produce. Proceedings 5th Controlled Atmosphere Research Conference, vol. 2, Wenatchee, Washington, p. 225. Martinez-Ferrer, M., Harper C., Perez-Muntoz, F., and Chaparro, M. 2002. Modified Atmosphere Packaging of Minimally Proce ssed Mango and Pineapple Fruits. Journal of Food Science Vol. 67, No. 9, 3365-3371. Meidner, H., and Mansfield, T. A, 1968. Physiology of Stomata. McGraw Hill Book Co. New York. Mencarelli, F., W.J. Lipton and S.J. Peterson. 1983. Response of zucchini squash to storage in low-O2 atmospheres at chilling and non-chilling temperatures. J. Amer. Soc. Hort. Sci. 108: 884-890. Moyls, L., Hocking, R., Beveridge, T. and Timbers, G. 1992. Exponential decay method for determining gas transmission rate of films. Trans. ASAE. 35(4), 1259-1265 Nobel, P. S. 1974. Introduction to Biophysi cal Plant Physiology. W.H. Freeman and Company, San Francisco Perry, R.H. and Green D., Perrys Chemical Engineers Handbook, 6th ed., McGraw-Hill International Editions, New York, 1984, 3-285. Renault, P., Souty, M. and Chambroy, Y. 1994a. Gas exchange in modified atmosphere packaging. 1: A new theoretical approach for microperforated packs. Intern. J. Food Sci. Technol. 29, 365-378.

PAGE 92

92 Renault, P., Souty, M., Houal, L. and Chambroy, Y. 1994b. Gas exchange in modified atmosphere packaging. 2: Experimental resu lts with strawberries. Intern. J. Food Sci. Technol. 29, 379-394. Robertson, Gordon L. 1993. Food Packaging Princi ples and Practice. New York, Marcel Dekker, Inc. pgs 75-77 Ryall, A. L. and W.J. Lipton. 1979. Handling, tran sportation and storage of fruits and vegetables. Vol. 1. Vegetables and melons. A VI, Westport CT. Ryall, A. L. and Pentzer, W.T. 1979. Handling Transportation of Fruits and Vegetables and Melons, Vol. 1. Vegetables and Melons, 2nd ed. AVI Publishing CT. Ryall, A. L. and Pentzer, W.T. 1982. Handling Transportation of Fruits and Vegetables and Melons, Vol. 2. Fruits and Tree Nuts, 2nd ed. AVI Publishing Co., Westport, CT. Saltveit, M.E. 1985. A summary of CA requi rements and recommendations for vegetables. Controlled atmospheres for storage and transp ort of perishable agricultural commodities. Blankenship, S. M. (Ed), Report No 126. De partment of Horticultural Science, North Carolina State University, Rale igh, North Carolina, USA. Wiley, R. C. 1994. Some Biological and Physical Principles Underlying Modified Atmosphere Packaging. In Minimally Processed Refriger ated Fruits and Vegetables, pg 183 225. Chapman & Hall Inc. New York.

PAGE 93

93 BIOGRAPHICAL SKETCH I was born in Bellows Falls Vermont and went to elementary, middle, and high school in the city of Tampa, Florida. My undergraduate stud ies were done in chemi cal engineering with a minor in material science at the University of Florida. Upon completion of my undergraduate studies I did one tour of duty in the US Navy. After completing my time in the US Navy I did my masters in Agricultural and Biological Engineer ing specializing in Packaging Science with a minor in Food Science also completed at the University of Florida.