Title Page
 Table of Contents
 Screening alternatives to sulfiting...
 Influence of washing and cooking...

Group Title: Technical paper -- Florida Sea Grant College Program ; no. 46
Title: Studies on the use of sulfites to control shrimp melanosis (blackspot)
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00075996/00001
 Material Information
Title: Studies on the use of sulfites to control shrimp melanosis (blackspot)
Series Title: Technical paper Florida Sea Grant College
Physical Description: 18 p. : ill. ; 28 cm.
Language: English
Creator: Florida Sea Grant College
Conference: Tropical and Subtropical Fisheries Technological Conference of the Americas, 1986
Publisher: Florida Sea Grant College
Place of Publication: Gainesville Fla
Publication Date: 1986
Subject: Shrimps -- Diseases   ( lcsh )
Sulphites   ( lcsh )
Melanosis   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references (p. 18).
General Note: Papers presented at the 11th Annual Meeting of the Tropical and Subtropical Fisheries Technological Conference of the Americas, January 14, 1986, at Tampa Florida.
General Note: "April 1986."
General Note: "Grant no. NA85AA-D-SG059."
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00075996
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 15236916


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Table of Contents
        Page 1
    Title Page
        Page 2
    Table of Contents
        Page 3
    Screening alternatives to sulfiting agents to control shrimp melanosis
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
    Influence of washing and cooking on sulfite residulas on treated shrimp
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
Full Text


TUhniod Papr No. 46



MIBl ErA- wcGRA a lrrlO



Project No. SGEP-8
Grant No. NA85AA-D-SG059

Technical Papers are duplicated in limited quantities for specialized audiences
requiring rapid access to information. They are published with limited editing
and without formal review by the Florida Sea Grant College Program. Content is
the sole responsibility of the author. This paper was developed by the Florida
Sea Grant College Program with support from NOAA Office of Sea Grant, U.S.
Department of Ccamerce, grant number NA85AA-D-SG059. It was published by the
Sea Grant Extension Program which functions as a component of the Florida
Cooperative Extension Service, John T. Woeste, Dean, in conducting Cooperative
Extension work in Agriculture, Hone Economics, and marine Sciences, State of
Florida, U.S. Department of Comnerce, and Boards of County Cmrmissioners,
cooperating. Printed and distributed in furtherance of the Acts of Congress of
May 8 and June 14, 1914. The Florida Sea Grant College is an Equal
Eaployment-Affirmative Action employer authorized to provide research,
educational information and other services only to individuals and institutions
that function without regard to race, color, sex, or national origin.

April 1986



Introduction. . . . . ... . . 1

Material and Methods . . . . ... . 1

Results and Discussion. . . . . ... 3

Summary . . . . . . . 8

References . . . . ... . . 10


Introduction. . . . . ... . 11

Materials and Methods . . . . .. 11

Results and Discussion . .. . . . .. .13

Conclusions . . . . ... ....... 18

References . . . . ... ....... 18

These papers were presented at the llth Annual Meeting of the Tropical and
Subtropical Fisheries Technological Conference of the Americas, January 14, 1986,
at Tampa, Florida. They will be included in the Conference Proceedings to be
published in 1987. Copies of the Proceedings will be available from Dr. Donn
Ward, 442 Kleberg, Texas A&M University, College Station, TX 77843.

Support for these projects was furnished by the Gulf and South Atlantic Fisheries
Development Foundation, Inc. and the National Fisheries Institute in cooperation
with the Florida Sea Grant College Program. Industry cooperation in harvest
and processing included shrimper Roy Toomer ("critter getter"), Jay-Tee Trawlers,
Inc., Leonard and Sons Shrimp Company, Singleton Seafoods/Con Agra, Inc., Bee
Gee Shrimp, Inc., and numerous industry associates.


Dr. W. Steven Otwell and Dr. Marty Marshall
University of Florida
Food Science and Human Nutrition Dept.
Gainesville, FL 32611


Shrimp melanosis, commonly known as 'blackspot' is a
harmless but objectionable surface dicoloration caused by
polyphenoloxidase enzyme systems which remain active during
refrigeration or ice storage. In the early 1950's sulfiting
agents, particularly sodium bisulfite was first introduced to
prevent or inhibit melanosis, thus yielding a more valuable
harvest (1). Such use of sulfites was 'prior sanctioned' by the
U.S. Food and Drug Administration (FDA) in 1956 (2). More
recent FDA decisions reaffirmed this practice (3), but
continuing regulatory scrutiny could restrict or eliminate the
application of sulfite on shrimp. The regulatory action is
prompted by an increasing concern for adverse 'allergic'
reactions most common amongst hyper-(sulfite) sensitive
asthmatics. Thus work was initiated to find alternatives to
replace or reduce the amount of sulfites required to inhibit
shrimp melanosis. This work would screen for possible
alternatives which would require subsequent verification with
field tests and statistical evaluations.


Preliminary investigations were necessary to describe the
rate and extent of shrimp melanosis. Samples of fresh,
untreated white shrimp (Penaeus setiferus) and pink shrimp (P.
duorarum) were observed in refrigeration. The occurrence of
melanosis was recorded in photographs to establish a subjective
scale for comparisons. The white shrimp (harvested off
Jacksonville and Apalachicola, FL) did not develop melanosis in
a consistent or predictable fashion. Attempts to induce
melanosis in white shrimp exposed to elevated oxygen levels in
sealed containers or ultraviolet lighting were unsuccessful.
The pink shrimp (harveted near Key West, FL) developed melanosis
in a predictable fashion usually first evident within 2 days on
ice and becoming progressively more prominent during subsequent
storage for 14 days. Thus pink shrimp was the choice species
for further tests relative to the scale developed to describe
melanosis (Table 1). This choice was consistent with the
original work by Camber et. al (4) which introduced the use of
sulfites through field tests with Key West, pink shrimp.

TABLE 1. Scale used to describe and rate the occurrence of melanosis (black-
spot) on pink shrimp.

Melanosis Scale

0 Absent
2 Slight, noticeable on some shrimp
4 Slight, noticeable on most shrimp
6 Moderate, noticeable on most shrimp
8 Heavy, noticeable on most shrimp
10 Heavy, totally unacceptable

TABLE 2. Compounds used individually and in mixtures to prepare dips for
treating fresh pink shrimp to control melanosis.

Compound Comments

Sodium Bisulfite Reducing agent
Sodium Bicarbonate Baking soda
Potassium Bromate Oxidizing agent; interact sulphydial transport
Calcium Chloride Geling agent; interfere oxygen
Erythrobate Acidulant, chelator, reducing agent
Ascorbic Acid Acidulant, antioxidant
Boric Acid Acidulant
Citric Acid Acidulant, antioxidant, chelator
Phosphoric Acid Acidulant
Sodium Tripolyphosphate Water control, sequestrant
Disodium phosphate Water control, buffer
Sodium Hexametaphosphate Water control, sequestrant
Ehtylere Diamine Tetra
Acetate Chelator
Glycine Complex with quinones
Taurine Bond sulfonic acid
Formaldehyde Complex with proteins
Hydrogen Peroxide Oxidizing and bleaching
BL7* Sulfite (67%) + phosphate + erythrobate +
phosphates + citrate + tartrate + glutamate +
tryptophan (descending order)

*Composition of BL7 provided by letter (1978) from Food Chemistry Division,
Environmental Sanitation Bureau, Ministry of Health and Welfare, Japanese


The melanosis scale can be related to existing
recommendations developed by the National Marine Fisheries
Service for grading raw shrimp (5). A scale rating of 4 cr
greater represents a measurable defect in product quality. A
rating of 8 or greater would represent a severe defect,
approaching unacceptable product.

Harvests were arranged such that the investigators obtained
fresh, heads-on pink shrimp while working on the vessel or
within less than 12 hours post-harvest at the dock. All shrimp
were routinely washed on-board and temporarily stored in ice.
The basic experimental procedure was to rinse 400-600 grams of
shrimp in 2.5 liters of variable dip compositions and
concentrations for 1 minute, then drain and package in plastic
bags to be stored in ice. The bags were considered necessary to
eliminate the variable influence of melting ice. Iced
containers with packaged shrimp were stored in 35 F (1.7 C)
refrigeration, and reicing every other day.

Development of melanosis was scored and photographed
routinely during 2 weeks storage. The bags of shrimp had been
numbered such that the investigator could not distinguish
amongst the various treatments. One experienced investigator
did all scoring relative to the aforementioned scale (Table 1).
The scale was accompanied by pre-developed color prints
depicting common examples of the advancing stages for melanosis.
The intent was to screen for obvious differences between
treatments, thus selecting the best treatments for subsequent
tests with statistical evaluations.

The various dips or chemical treatments included controls
(no treatment), customary sodium bisulfite used in varying
concentrations, and a variety of single compounds and/or
mixtures prepared in varying concentrations (Table 2). The dip
solution was fresh tap water.

Two field trials (I and II) were necessary to accommodate
all the variable treatments. Trial I was for shrimp harvested
6/26/85 and Trial II commenced 12/13/85. Water temperatures and
atmospheric conditions were clear and similar in Key West during
both harvests. The common practice for pink shrimp is night
harvest, thus avoiding influence of sunlight. One set of
controls (no treatment) and bisulfite treatments were included
for each trial to account for any variations amongst shrimp per
harvest. Trial II included an additional series of treatments
using 3.5% saltwater as the dip solution. The saltwater was
made from the same source of fresh tapwater plus 3.5% commerical
marine (aquarium) salts.


Preliminary experience in developing a rating scale with
accompanying photographs depicting the degrees for melanosis

proved successful. Rating for controls and bisulfite
treatments were similar for both trials (compare Table 3 and 4).
Melanosis on pink shrimp seem to progress in a linear manner.
In controls, melanosis was obvious within 3 days, becoming a
defect within 5 days, and approaching a severe defect
(unacceptable) on day 7. Thus pink shrimp was a practical test
species as opposed to white shrimp which in some instances did
not display melanosis.

All bisulfite treatments (0.25,.to 2.50% dips) inhibited the
onset of melanosis (Talbe 3 and 4). The most effective
concentration was 2.50%, thus demonstrating the encouragement
for employing treatments in excess of the legally recognized
1.25% dip for 1 minute. The 1.25% bisulfite dip inhibited
melanosis until blackening was only slightly noticable on some
shrimp after 12 days storage. Melanosis increased to a
measureable defect on day 12 after treating with 0.25 and 0.50%
dip concentrations.

No treatments in Trial I were as effective as 1.25% sodium
bisulfite. The next effective treatment was the commercial
preparation, BL7. The inhibitor influence of BL7 at a dip
strength of 1.0% was similar to sodium bisulfite at 0.50%. This
is expected relative to the formulation for BL7 which is 67.2%
sodium hydrogen sulfite. Thus a 1.0% BL7 dip contains the
equivalent of 0.67% sodium bisulfite.

A variety of chemical combinations (treatments no. 4-8)
provided initial inhibition still evident on the 7th day of
storage (Table 3). All of these mixtures contained some level
of bisulfite (0.25 or 0.50%). After 12 days storage, shrimp
from all these treatments exceeded a score of 6 and some were
judged unacceptable. Thus the influence of the other
constituents (Asc, DSP, EDTA, SHP, or STP) did not enhance the
influence of bisulfite over that recorded for similar,
individual bisulfite treatments (0.25 and 0.50%). This suggests
the bisulfite provided the dominant influence in these mixtures.
The mixture which included ascorbate (treatment no. 4) appeared
to have an objectionable yellow tint obvious on day 3.

All remaining dips in Trial I (treatment nos. 9-17)
resulted in melanotic shrimp scored within the 3rd day of
storage (Table 3). Despite the early onset of melanosis after
dips with STP (4.0 and 8.0%) and Ery/EDTA (1.0/0.1%), the final
melanosis rating on day 12 did not exceed 6, suggesting some
partial control. The adverse results after sodium bicarbonate
dips dispell some fishermen's common belief that baking soda can
prevent melanosis. Treatments with calcium chloride, hydrogen
peroxide and potassium bromate promoted melanosis.

Results from Trial II reaffirm the distinct influence of
bisulfite dips (Table 4). Again, the mixtures which were less
effective, but approximating the influence of bisulfite dips,

TABLE 3. Trial I. Ratings for the occurrence of melanosis on pink shrimp in
refrigerated storage (per day) after treatment in a variety of dips
for 1 minute. The dip solution was fresh tapwater. After controls
the treatments are numbered and placed in a general order for de-
creasing effectiveness.

Trt. Dips Day Storage Trt. Dips Day Storage
No. % 3 7 12 No. % 3 7 12

1. Control (No dip) 2-3

2. Sodium Bisulfite
0.25 2
0.50 0
1.25 0
2.50 0

3. BL 7 (Commercial)
0.25 0
0.50 0
1.00 0

4. Bis/EDTA/Asc
0.5/0.1/1.0 2
0.25/0.1/1.0(y) 0

5. Bis/STP
0.5/2.0 0
0.5/5.0 0
0.25/2.0 2
0.25/5.0 0

0.5/0.1/1.0 0
0.5/0.1/2.0 0
0.5/0.1/4.0 0

0.25/0.1/2.0 0
0.25/0.2/2.0 2
0.25/0.2/5.0 0
0.25/0.1/5.0 0
0.50/0.1/2.0 0
0.50/0.2/5.0 0

0.5/0.1/1.0 0
0.5/0.1/4.0 2

7-9 10 9. Ery/EDTA

2 4 6

10. STP

11. Phosphoric Acid


13. Sodium Bicarbonate

14. Asc/EDTA

3 8 10

15. Calcium Chloride

16. Hydrogen Peroxide

17. Potassium Bromate

Asc = Ascorbic Acid
Bis = Sodium Bisulfite
Cit = Citric Acid
DSP = Disodium Phosphate
EDTA = Ethylene Diamine Tetra Acetate
Ery = Erythrobate

= Sodium Hexameta phosphate
= Sodium Tripolyphosphate
= Commercial melanosis inhibitor
= yellowing


TABLE 4. Trial II. Ratings for the occurrence of melanosis on pink shrimp in
refrigerated storage (per day) after treatment in a variety of dips
for 1 minute. The dip solution was fresh tapwater. Ratings within
parenthesis are for shrimp treated when the dip solution was 3.5%
saltwater (commercial marine salts.). After controls, the treatments
are numbered and placed in a general order for decreasing effective-
Days Storage
DIP %'s 3 5 7 12

1. Control (no dip)
freshwater rinse 2-4 5-6 7-9 10
saltwater rinse (4-5) (5-7) (9-10) (10)

2. Sodium Bisulfite
0.25 0(0) 0(0) 6(2) 6(5)
0.50 0(0) 1(0) 2(4) 6(5)
1.25 0(0) 0(0) 0(2) 2(4)
2.50 0(0) 0(0) 0(0) 0(2)

3. Bis/EDTA/Cit.
0.5/0.1/0.5 0(0) 0(1) 2(4) 5(3)
0.5/0.2/0.5 0(0) 0(0) 2(3) 3(5)
0.25/0.1/0.5 0(0) 0(1) 3(5) 3(5)
0.25/0.2/1.0 0(0) 2(2) 3(5) 4(6)

4. Boric Acid
0.5 0(0) 0(0) 5(5) 6(7)
1.0 0(0) 0(0) 1(3) 4(2)

5. Bis/Cit
0.5/0.5 0(0) 1(0) 4(5) 4(4)
0.25/1.0 0(0) 3(2) 5(6) 7(5)
0.25/0.5 0(0) 2(1) 4(5) 8(4)

6. Bis/Ery
0.5/0.5 0(0) 0(0) 1(2) 2(4)
0.5/0.1 0(0) 1(2) 4(7) 4(6)
0.25/0.5 0(0) 2(5) 3(10) 6(10)
0.25/0.1 0(0) 2(3) 7(4) 6(10)

7. Bis/EDTA
0.5/0.5 0(0) 2(3) 5(7) 5(4)
0.5/0.2 0(0) 1(3) 5(6) 5(5)
0.25/0.1 0(0) 1(2) 4(7) 5(5)
0.25/0.2 0(0) 3(5) 6(6) 5(7)

TABLE 4 continued

8. Asc/Cit
1.0/1.0(Y) 0(0) 1(1) 5(4) 9(2)
1.0/0.5(Y) 1(1) 5(4) 5(5) 7(5)
0.5/1.0(Y) 0(0) 1(1) 5(7) 1(1)
3.0/1.0(Y) 1(0) 1(1) 1(3) 1(1)
9. Formaldehyde
0.5 0(0) 2(4) 3(7) 10(7)
1.0 0(0) 2(1) 4(1) 7(7)
0.5/0.1/0.5 0(0) 2(2) 6(5) 7(7)
0.25/0.1/0.5 0(0) 2(2) 6(7) 7(7)
0.25/0.2/1.0 0(0) 1(2) 7(7) 8(7)

11. EDTA
0.1 2(2) 3(2) 5(5) 5(4)
0.2 2(2) 5(3) 6(5) 5(5)
0.4 2(2) 3(2) 5(5) 5(5)
0.5/0.1/0.5 0(0) 3(5) 9(7) 10(10)
0.1/0.2/0.5 0(0) 5(5) 8(8) 10(9)
0.5 1(1) 4(4) 9(8) 10(10)
1.0 1(2) 4(4) 7(6) 10(10)
0.5 1(1) 4(4) 8(7) 10(10)
1.0 1(1) 4(7) 9(9) 10(10)
0.1 3(3) 5(5) 10(9) 10(10)
0.5 4(3) 6(5) 8(7) 10(10)
1.0 3(3) 5(5) 5(9) 10(10)
0.5 3(3) 7(6) 9(10) 10(10)
1.0 3(3) 7(7) 9(10) 10(10)

ASC = Ascorbic Acid
Bis = Sodium Bisulfite
Cit = Citric Acid
Ery = Erythrobate
EDTA = Ethyl Diamine Tetra Acetate
(Y) = Noticeable yellowing

all included a portion of bisulfite (treatments nos. 3 and 5-7).
The most effective mixtures amongst these treatments were
essentially equivalent to a 0.50% bisulfite dip and not better
than a 1.25% bisulfite dip (Figure 1). The most effective
mixture was Bis/Ery (0.5/0.5%), but this effect was not
substantiated by similar dips including EDTA (treatments no.
10). All of these moderately effective mixtures contained a
portion of bisulfite (0.25 or 0.50%). The mixtures with 0.50%
bisulfite appeared superior to similar mixtures with less
bisulfite (0.25%). For example, the Bis/Cit dip at 0.5/0.5%
provided more prolonged control of melanosis than did the
mixtures of 0.25/0.5% or 0.25/1.0%. These results again suggest
the dominant influence of bisulfite.

Although boric acid and formaldehyde are not included on
the U.S. Food and Drug Administration's 'GRAS' list (generally
recognized as safe), these dips provided some inhibition, thus
demonstrating the influence of acidulants and protein binding
(Table 4). The Asc/Cit dip retarded melanosis, yet produced a
distinct yellowish tint obvious from day 3 through 7.
Additional dips (treatments no. 11-16) were least effective,
some yielding unacceptable shrimp within 7 days storage.

In Trial II the melanosis rating in parenthesis per
treatment and day of storage are results for shrimp rinsed in
dips made with 3.5% saltwater (Table 4). General comparisons
with the complementary tapwater dips indicate a more favorable
response, or less melanosis after freshwater dips. This
observation is preliminary and restricted to interpretation
relative to the use of a marine (aquarium) grade salt mixture.
Further field work with statistical designs and actual seawater
(as may be used by the fishermen) would be required before
concluding recommendations.


1. The choice of shrimp species can influence the occurrence of
melanosis and the interpretation of tests to develop
alternatives to sulfites. The results from this study are
relative to the use of pink shrimp (Penaeus duorarum).

2. Raw, untreated pink shrimp develop melanosis in a linear
manner, initially obvious on some shrimp within 3 days
refrigerated storage and progressing as a severe product
defect after 7 days. Thus pink shrimp require some
measures to prevent melanosis to assure marketability.

3. A 2.50% bisulfite dip (1 minute) was more effective in
preventing melanosis than was the legally recognized 1.25%
bisulfite dip.

4. The 1.25% bisulfite dip (1 minute) was superior in
preventing melanosis than was any treatment, single

Figure 1.

Ratings for the degree of melanosis
on pink shrimp following treatment
in a variety of alternative dips
(% composition) and sodium bisulfite
dips (0.50 and 1.25%).



Figure 2.

BIS/EDTA (.5/.2)
BIS/CITRIC (.5/.5)
BIS/EDTA/CITRIC (.5/.2/.5)


3 5 7 1Z

Ratings for the degree of melanosis
on pink shrimp following treatment
in dips with varying mixtures
(% composition) of sodium bisulfite
(Bis) and citric acid (Cit).

2. IlS/CIT


.J 4


compounds or mixtures, used in this study.

5. Comparative results suggest dips containing mixtures of
bisulfite plus citric acid, erythrobate, and/or EDTA could
offer moderate prevention of melanosis. These mixtures
are more effective at higher bisulfite concentrations.
The bisulfite appears to impart a dominant influence.

6. Further field trials approximating actual fishing practices
and employing statistical evaluations are necessary to
verify the effectiveness of mixtures including bisulfites,
citric acid, erythrobate and/or EDTA This work could also
evaluate the influence of freshwater vs. seawater as the
dip solution.


1. Alford, J.A. and E.A. Fieger. 1952. The non-microbial
nature of the blackspots on ice-packed shrimp. Food
Tech. 6:217-219.

2. Camber, C.I., M.H. Vance and J. Alexander. 1956. How
to use sodium bisulfite to control 'blackspot' on shrimp.
Univ. Miami Special Bull. No. 12. 4 pp.

3. Federal Register. 1982. (July 9) Sulfiting Agents:
Proposed affirmation of GRAS status with specific
limitations. 47 (132) 29956-29963.

4. Camber, C.I., M.H. Vance, and J.E. Alexander. 1957.
The use of sodium bisulfite for the control of blackspot
in shrimp. Univ. Miami. Tech. Series No. 20, 19 pp.

5. Code Federal Regulations. (1982) Title 50, Part 265,
Subpart A. United States General Standards for Grades
of Shrimp. pp. 262-268.


The work was supported in part by the Gulf and South
Atlantic Fisheries Development Foundation, Inc. (Tampa). Field
work was assisted by Florida Sea Grant Marine Extension Agents,
John Stevely (Bradenton) and Frank Lawlor (Palm Beach).


Dr.Marty Marshall and Dr. W. Steve Otwell
University of Florida
Food Science and Human Nutrition Dept.
Gainesville, FL 32611


Roy E. Martin
National Fisheries Institute
Washington, D.C.


Sulfiting agents as food additives have come under close
scrutiny due to possible adverse health problems, most common
amongst certain asmatics, such as nausea, diarrhea,
anaphylactic shock, loss of consciousness, and possible death
(Hecht and Willis, 1983). This has caused various federal,
state and local food regulatory agencies to propose limiting
the residual sulfite on food products. The FDA has placed an
acceptable residual sulfite level on shrimp at 100 ppm as SO.
Thus, shrimp containing residual sulfite greater than the 100
ppm level would be considered adulterated (CFR. 1985).

Processor's concerns that shrimp (either domestically
produced and/or imported) meet FDA guidelines, have prompted
interest in the possibility of reclaiming adulterated product.
Processors, consumers, scientists, and regulatory agencies
have inquired about the effect of various cooking methods on
the residual sulfite of shrimp. The Codex Alimentarius
Commission Standards are 100 ppm (SO2) residual on raw edible
product and 30 ppm on cooked product (FAO/WHO, 1984; CFR.
1984). This international recommendation lacks analytical
verification. Therefore, the objective of this work was to
examine the effect of cooking on residual sulfite levels and
to compare the effectiveness of various reclamation (washing)
treatments on lowering excessive sulfite residuals.



Headless, shell-on white shrimp (Fenaeus setiferus),
medium size were obtained immediately post-harvest,
transported to the Food Science and Human Nutrition Dept. and
stored on ice for 1 day. The fresh shrimp were treated with
various bisulfite dips (0.5, 1.25, and 2.0% Na2S205, for 1
min), drained (30 sec), and all samples were stored frozen

(-300C). A portion of the shrimp was commercially breaded
with "Golden Dip + DCA" batter. Cooking treatments included:
boiling, shell-on and -off; broiling, shell-on; saut6, shell-
off; and frying, shell-off/breaded.

Shrimp (400-500 g) were thawed overnight at room
temperature, mixed and drained for 1 min and then divided into
two groups of approximate equal weights. Group 1 (control)
were raw shrimp, shell-off, which were then chopped, combined
and four samples (40-50 g) were weighed, to determine residual
sulfite levels. Group 2 (cooking treatments) were shrimp
which would be cooked to an internal temperature in excess of
1700C using the following cooking protocol:

Boilina Shell-on or -off: Place 200-250 g shrimp
,in 2 1 of vigorously boiling tap water for 1.5 min.
After cooking, drain and cool to room temperature.

Broilinc Shell-on: Preheat oven 10 min on broiler
setting, place 200-250 g shrimp on flat pan and
place on rack set at second division, 6 inches from
the heating coil (approximately 2130C). Cock for
2.5 min and then turn shrimp over and cook another
2.0 min. Drain and cool to room temperature.

Saut6 Shell-off: Place 15 g of vegetable oil in a
teflon pan, heat on a setting of 7 (approximately
199-2040C), and spread shrimp (200-250 g) in pan
making sure shrimp are always in contact with the
surface. Cook for 2.5-3.0 min with constant
stirring and making sure shrimp are turned at least
once. Drain and cool to room temperature.

Frying Breaded, Shell-off: Preheat oil in deep-fat
fryer until temperature reaches 1490C (use fresh
vegetable oil each time). Place shrimp (200-250 g)
in fryer and cook for 2-3 min. Remove shrimp and
place on paper towel to drain and cool to room

Shrimp cooked with shell-on had the shell removed prior
to analysis. The edible portion of shrimp for each cooking
treatment was chopped, combined, and four samples (40-50 g)
analyzed for residual sulfite according to standard AOAC
Monier-Williams (M-W) method (AOAC, 1980). The breaded shrimp
(frying) were analyzed with breading included as part of the
edible portion. An additional experiment was performed as
above, however, for the frying treatment, the breading was
removed before M-W analysis.

Two sizes of frozen shrimp (16/30 and 51/60 individual
count/lb) having adulterated levels (>100 ppm) of sulfite were
obtained from a commercial processor. Three boxes or 15 lb
from each size remained frozen as a control. The remaining
shrimp were subjected to various reclamation treatments (trt.)
using 2 boxes (10 lb) per size per treatment. The frozen
shrimp were thawed in flowing water with in-line chlorine
(less than 10 ppm) and re-frozen (Thawed trt.), while more
shrimp were thawed as above and then commercially peeled and
re-frozen (Thawed/Peeled trt.). The final treatment was
thawing more of the same shrimp as above, commercially peeling
and then washing in flowing cold water (less than 4.40C) with
in-line chlorine (less than 10 cm) for 30 min and re-freezing
(Thawed/Peeled/Washed trt.). Samples from the controls and
three treatments were brought to the Food Science and Human
Nutrition Dept., Gainesville, FL for sulfite analysis (M-W

Pink headed shrimp (Penaeus ducrarum), medium size were
obtained immediately post-harvest and transported on ice to
the Food Science and Human Nutrition Dept., Gainesville, FL.
Fresh shrimp were dipped in 1.25% and 2.5% Na2S205 for 1 min,
and a portion of the shrimp from each sulfite dip were frozen
for a control. A portion of the remaining shrimp were dipped
in ozonated water (1 mg ozone/l water) for 5 min at a ratio of
1 lb per gallon and frozen (-300C) until analyzed. Ozone was
generated using a portable ozone generator, model 25 HF-1000
(OPT Systems, Inc., Arlington, VA). The remaining portion of
fresh shrimp was divided into thirds and treated either by
dipping in 3% hydrogen peroxide (H202), soda or seltzer water
for 5 min, then drained and frozen (-300C) until analyzed.
Sulfite analysis on edible tail was performed for all
,reclamation samples using M-W method.


Two cooking methods (broil and fry) did not significantly
(a=0.05) reduce residual bisulfite on shrimp (Table 1). A
significant (a=0.05) reduction in bisulfite levels occurred at
the higher dip (2.0%) concentration for boiled shell-on and
shell-off when ANOV and multiple comparison (Duncan) analysis
were performed. However, this reduction only averaged
ap-prximately 23%. High intensity ccoking, sauti, caused a
significant (a=0.05) reduction in residual bisulfite levels at
all dip concentrations (Table 1). Reductions of 52, 51 and
28% resulted during saut6 cooking for 0.5, 1.25, and 2.0% dip
concentrations, respectively.

The Codex Alimentarius Commission (CAC) standard for raw
edible shrimp is 100 ppm as SOl and 30 ppm on cooked shrimp
(FAO/WHO, 1984; CFR. 1984). This recommendation implies
cooking causes a 70% reduction in residual bisulfite. Our
results are contradictory to the CAC standard, indicating the
residual bisulfite from the raw product is not reduced by most
common cooking methods. Because of the potential significance
of this finding, a second experiment was performed.

Table 1. Residual bisulfite levels (ppm as S0o) on shrimp
after various cooking methods: Experiment 1.

Dip Concentration

0.5% 1.252 2.0%
trt. Raw Cook Raw Cook Raw Cook

Boiled (shell)
-on 72 30 65 32 133 17 124 23 301 100 258 75
-off 42 2 66 30 141 16 115 21 270 18 197 21
Broiled 41 8 52 5 188 9 184 6 215 13 230 10
Fry 44 25 46 28 72 15 63 30 112 30 89 16
Saut6 46 6 22 3 150 10 73 13 230 29 169 22"

1Mean s.d., n=7 replications.
Numbers followed by an (*) are significantly different
'(c=0.05) from the raw sample (Duncan's Multiple Comparison).

The second ANOV demonstrated that four of the five
cooking methods: boiling, shell-on, -off; broiled; fry; again
did not cause significant (<=0.05) reductions in residual
bisulfite levels at lower dip concentrations (Table 2). A
reduction in residual bisulfite on shrimp may result at the
2.0% dip treatment for these four cooking methods, but the
reduction again only averaged 21% (Tables 1 and 2). The
second experiment confirmed the results of the first and also,
contradicts the CAC standard for cooked shrimp. High intense
cooking again caused significant reductions in residual
bisulfite levels from uncooked product (Table 2).

Table 2. Residual bisulfita levels (ppm SO2) on shrimp after
various cooking methods: Experiment 2.

Dip Concentration

0.5% 1.25% 2.0%
trt. Raw Cook Raw Cook Raw Cook

Boiled (shell)
-on. 28 2 25 2 78 18 58 4 131 10 99 11
-off 22 2 15 2 56 10 58 6 115 13 130 25
Broiled 27 2 28 2 64 10 66 _6 120 7 97 7,
Saut6 21 7 5 0 55 6 19 2" 110 11 63 2

1Mean s.d., n=4 replications.
Numbers followed by an (*) are significantly different
(a=0.05) from the raw sample (Duncan's Multiple Comparison).

Analyzing fried shrimp with (+) and without (-) breading
indicates sulfites do not seem to migrate into the breading
upon frying and the breading actually "dilutes" the amount of
residual bisulfite on the edible portion of shrimp (Table 3).

Reclamation Effects

Thawing, and thawing and peeling resulted in an
approximate 14-20% reduction in residual sulfite on this
commercial product (Table 4). Thawing, peeling and then
washing for 30 min reduced the residual sulfite levels by 40%.
The percent reduction per treatment was similar for either
size shrimp. Thus reclamation by common procedures (thawing,
peeling, and washing) used in .commercial shrimp processing can
reduce the concentration of residual sulfites, but the percent
reduction is limited.

Table 3. The influence of breading on residual bisulfite
levels (ppm as SO2) in fried shrimp.

1.25% Dipped Treated Shrimp

+ BreadingI Breading1
Trials Raw Cooked Raw Cooked

1 41 46 63 60
2 33 41 64 59
3 36 36 56 79
4 41 50 71 59

X sd = 38 4 43 6 54 6 64 10

1 )Breading implies M-W analysis with (+) or without (-)
breading present on fried shrimp.

Ozonated water did not reduce the residual bisulfite
levels on shrimp at the 1.25% dip but did reduce (16%) the
level on the 2.5% dipped shrimp (Table 5). Again a wash
treatment was more effective at a higher residual level, but
the ozone treatment enhanced subsequent melanosis. Hydrogen
peroxide did reduce substantially the levels of sulfite on
'shrimp at all dip treatments and the reduction was within FDA
guidelines (Table 5). However, the shrimp turned severely
melanotic after this treatment and were considered an inferior
product. Soda and seltzer water reduced sulfite levels on
shrimp approximately 60% and resulted in FDA borderline levels
on shrimp. The product appeared to remain free of blackspot
after this reduction. Since the chemical washes were applied
fairly soon (10-15 min) after bisulfite dipping, a water
control must be performed to fully evaluate these treatments.
However, soda and seltzer water, unlike ozone and H202, appear
to protect the shrimp from further melanosis after washing.

Table 4. Reclamation of a commercially abused shrimp product
after thawing, peeling, and washing treatments.

M-W Sulfite1
(ppm as SO2) % Reduction

Treatment LG2 SM2 LG SM

(control) 250 188 -
Thawed 216 150 14 20
Thawed and
Peeled 216 168 14 11
Thawed and
Peeled and
Washed 154 111 38 40

1Values are averages of two boxes with two reps. per box.
2Large (LG) size, 26-30 count/lb; Small (SM) size, 51-60/lb.

Table 5. Reclamation of shrimp dipped in 1.25 and 2.5% Na2S205
for 1 min and then dipped in ozonated water, H202, and soda
and seltzer water.

Average M-W Valuel
(ppm as S02)



control wash control wash

Ozone water 127 18 180 7 309 20 260 20 (16)3
3% H202 127 18 78 6 (38) 309 20 86 9 (72)
Soda -267 35 105 7 (61)
Seltzer -267 35 99 17 (53)

2Mean s.d., n=4.
2Shrimp were dipped in bisulfite then re-dipped in the
corresponding treatment usually for 5 min.
3Values in () are the % reduction from control.



Most typical cooking methods offer little advantage in
reducing sulfite levels on shrimp. If there is a reduction in
sulfite, it occurs at the higher dipping concentration (2.0%);
Higher dip concentration may yield a higher portion of free
(SO2) residual. High intensity cooking such as saut6
dramatically reduced the residual bisulfite levels on shrimp
at all dip concentrations. It would appear, the CAC standard
of 30 ppm SO2 on cooked product must be re-evaluated.

Thawing, peeling and washing can reduce residual (SO,)
sulfite levels on adulterated shrimp, but the percent
reductions are limited. The reductions observed were similar
for small (51/60) or large (26/30) shrimp.

Ozone reduced (16%) residual bisulfite on the 2.0% dipped
shrimp but failed to lower residual levels at 1.25% dip.
Hydrogen peroxide (3%) treatment did significantly lower the
residual bisulfite on shrimp but melanosis resulted producing
an inferior product. Soda and seltzer water dips also
resulted in a reduction of residual bisulfite on shrimp.
Unlike the H202, these treatments do not seem to promote


A.O.A.C. 1980. "Official Methods of Analysis," 13th ed.
Association of Official Analytical Chemists, Washington, D.C.

CFR. 1984. "Code of Federal Regulations. Title 21 Food and
Drugs" Part 161, vol. 49(7), Office of the Federal Register,
'National Archives and Records Service, General Services
Administration, Washington, DC.

CFR. 1985. "Code of Federal Regulations. Title 21 Food and
Drugs" Part 182. Office of the Federal Register, Naticnal
Archives and Records Service, General Services Administraticn,
Washington, DC.

FAO/WHO. 1984. "Codex Alimentarius, Recommended International
Code of Practice for Shrimp or Prawns," vol. B, 2nd ed. Joint
FAO/WHO Food Standards Prograne, FAO, Rome.

Hecht, A. and J. Willis. Sulfites: Preservatives that can cc
wrong. FDA Consumer, p. 11.

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