Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 57-3
Title: Investigations concerning factors affecting the quality of frozen grapefruit concentrate
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Permanent Link: http://ufdc.ufl.edu/UF00072380/00001
 Material Information
Title: Investigations concerning factors affecting the quality of frozen grapefruit concentrate
Series Title: Citrus Station mimeo report
Physical Description: 4, 9 leaves : ; 28 cm.
Language: English
Creator: Wenzel, F. W
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
Publisher: Florida Citrus Experiment Station :
Florida Citrus Commission
Place of Publication: Lake Alfred FL
Publication Date: 1956
 Subjects
Subject: Grapefruit juice -- Quality -- Florida   ( lcsh )
Concentrated fruit juices -- Quality -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: F.W. Wenzel ... et al..
General Note: Caption title.
General Note: "October 11, 1956."
 Record Information
Bibliographic ID: UF00072380
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74670076

Full Text

f. ^ i-




Citrus Station Mimeo Report 57-3
October 11, 1956


Investigations Concerning Factors Affecting the Quality of Frozen
Grapefruit Concentrate

F. W. Wenzel, R. W. Olsen, E. L. Moore, R. L. Huggart, C. D. Atkins,
A. H. Rouse, S. V. Ting, E. C. Hill, E. J. Deszyck,
R. Patrick and R. W. Barron


Several investigations were instigated during the 1955-56 season to determine
factors that affect the quality of frozen grapefruit concentrate. Data from these
studies may indicate ways for improving the quality of this product, so that it
may meet with greater consumer acceptance which would result in increasing the
utilization of grapefruit for the production of concentrate. Two of these in-
vestigations were undertaken at the request of the Quality Advisory Committee of
the Florida Canners' Association. Results obtained to date from these and one
other study will be briefly discussed in this report.

Examination of commercial samples of frozen concentrated grapefruit juices. -
With the assistance of personnel of the U.S.D.A. Agricultural Marketing Service,
samples from 28 packs of commercial frozen grapefruit concentrate were collected
from 11 plants during the 1955-56 season. The number of packs, from which samples
were obtained, ranged from 1 to 7 for any 1 plant. The dates of packing ranged
from approximately the middle of December until the middle of April, however, 20
of the packs were processed in March Er April. The minimum, maximum, and average
values for characteristics of the samples from the 28 packs of frozen grapefruit
concentrate are presented in Table 1. None of these samples showed any initial
clarification or gelation and after storage at 800F. for 24 hr., slight gelation
was noted in only 2 samples and a semi-gel formed in 1 sample; under the same
conditions of storage, definite clarification occurred in 2 samples and extreme
clarification in 6 samples. Neither clarification nor gelation occurred in any
of the 28 samples after storage at 400F. for 48 hr. Plate counts were made
using 9 of the samples and these counts were found to be so low that plating of
the other samples was not done. Examination of all of the data now available has
not yet been made to determine relationships between the various characteristics
of these grapefruit concentrates.

Each of the reconstituted frozen grapefruit concentrates were submitted
twice to a taste panel for evaluation of flavor according to instructions which
are included in this report. The juices were at room temperature when tasted
and only three juices were evaluated at any one time by the panel, which ranged
from 5 to 9 persons. In evaluating the results obtained, the flavor grades given
by all panel members to a sample of reconstituted juice were averaged and this
average grade determined the flavor quality for the concentrate provided a
majority of the panel members had so classified this product: however, if the
average grade was greater or smaller than that indicated by the majority of the
panel members then the opinion of the majority was used. A greater variation


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718 10/11/56 FW.-'









-2-


was noted in the flavor grades designated by each of the panel members for many
of the grapefruit juices, than that usually found when reconstituted frozen
orange concentrates had been graded by the same taste panel; therefore, the
opinion of the majority of the panel had to be used quite often, rather than the
average grade. Results indicated that the 28 commercial frozen grapefruit con-
centrates were graded as follows: 14 = Good (7), 13 = Fair (6) and 1 = Fair (5).
Flavor defects were noted by panel members for many of the products and all of
the flavor defects listed on the instruction page were mentioned except heated,
immature and overmature fruit. Defects most frequently mentioned were bitter and
the "oxidized" (COF) off-flavors, such as tallowy and castor oil. Flavor defects
designated for the same sample by different persons varied greatly and the
majority of the panel did not note the same defect for any one of the 28 samples
that were tasted and, therefore, the occurrence of such off-flavors in the grape-
fruit concentrates was not considered to be very significant. Such results
indicate that in evaluating grapefruit products for flavor defects perhaps only
one or two specific defects should be checked at any one time.

Examination of experimental packs of frozen concentrated grapefruit juices. -
The purpose of another investigation was to obtain data that might indicate the
relationship between the quality of raw grapefruit juice and that of the frozen
grapefruit concentrate produced from it. Fruit from different localities was
obtained and 11 lots were processed in the pilot plant. Raw juice from each lot
of fruit was canned, frozen and stored at -80F. for future examination depending
upon the quality of the frozen grapefruit concentrate produced. The date of
packing, the source of fruit and some of the characteristics of the raw juices
extracted from the 11 lots of grapefruit are shown in Table 2. o Brix ranged from
9.10 to 13.90; acid from 0.90 to 1.73%; ratio from 7.2 to 10.4; and pulp from 5.0
to 22.0% by volume. All lots of fruit were extracted on a FMC In-Line extractor
and a 0.020 inch finisher screen was used in all instances, except for the lots
extracted on March 23, 27 and 28 when a 0.030 inch screen was used. The finished
juices were stabilized by heating to 1950F. in a Walker-Wallace plate type ex-
changer prior to concentration in pilot plant evaporator. The concentrated juices,
approximately 50 Brix, were cut back to 380 Brix using unheated juices; also
using these 500 Brix concentrates, 19 packs containing added sugar were prepared.
These packs containing sugar were made by adding either or both the minimum and
maximum amounts of sugar so that the finished products would contain 36% juice
solids, o Brix from 380 to 480, and ratio from 10 to 13. Coldpressed grapefruit
oil was added to the sugar-added packs on the basis of 0.03 ml./lOOg.; oil was
not added to the 380 Brix unsweetened products. All of the products were canned,
frozen and stored at -80F. The minimum, maximum and average values for character-
istics of the eleven 380 Brix unsweetened frozen grapefruit concentrates are listed
in Table 3. When these products were stored at either 400F. for 48 hr. or 800F.
for 24 hr., neither clarification nor gelation occurred in any of them. Data now
available from the examination of these 11 unsweetened and 19 sweetened experi-
mental packs of concentrates have not yet been completely analyzed to determine
if there is any correlation between their different characteristics and the
quality of these products or the raw juices from which the concentrates were
made.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718a 10/11/56 FWW







-3-


The flavor of these 30 packs of frozen concentrated grapefruit juices has
been evaluated by the Station taste panel and also by quality control personnel
of 5 commercial plants. The samples were graded and results analyzed using the
same instructions and procedure as previously discussed in this report. Recon-
stituted juices from each of the 30 packs were tasted by from 31 to 42 persons.
The results indicated great variations in the grade given to the same juice by
different persons, as well as differences in the kinds of flavor defect noted;
thus these results were similar to those observed when the flavor of commercial
frozen grapefruit concentrates was evaluated by the Station panel. Summaries
are shown in Tables 4, 5 and 6 which are based on the acceptability of the 30
experimental packs as indicated by a flavor grade of 5 or better. These results
indicated a definite preference for sweetened concentrates; also a slight prefer-
ence for the sweetened products that contained a minimum amount of added sugar.
Flavor defects most frequently indicated as reasons for poor flavor quality in
the reconstituted juices were as follows: unsweetened concentrates sour, bitter,
"oxidized" (COF), astringent and weak; concentrates with minimum added sugar -
bitter, sour and weak; and concentrates with maximum added sugar sweet, bitter,
"oxidized" (COF) and weak.

Effect of maturity of fruit on the quality of frozen concentrated grapefruit
juices. Prior to the previously mentioned requests of the Quality Advisory
Committee, an investigation was started at the Station to determine the effect
of fruit maturity on the quality of frozen grapefruit concentrates. During the
1955-56 season, packs of frozen concentrates were made from fruit obtained from
Station groves. The processing dates are given in Table 7, as well as information
on characteristics of the concentrates; Duncan and Marsh grapefruit were used and
the fruit was obtained from the same plots throughout the season. Arsenated fruit
and unarsenated fruit of both varieties were used. Packs were first processed on
January 4 and the last packs were processed on June 29. The o Brix of the raw
juices ranged from 9.20 to 12.90; acid from 0.78 to 1.99%; and ratio from 6.1 to
12.8. The fruit was extracted on a Citro-Mat extractor and the juice finished
using a 0.030 inch screen. The juices were stabilized by heating to 1950F. in a
Walker-Wallace plate type exchanger, prior to concentrating in pilot plant evap-
orator to approximately 500 Brix. The concentrated juices were cut back to 380
Brix, using both heated and unheated cut back juices. Packs of the 500 Brix
concentrates into which air was whipped, as well as control packs of these con-
centrates into which air was not intentionally incorporated, were also prepared
to study the development of COF or "oxidized" off-flavors. All of these products,
a total of 80 packs, were canned, frozen and stored at -80F.

The Brix, acid content and ratio of the 20 packs of 380 Brix frozen grape-
fruit concentrates that contained unheated cut back juices are listed in Table 7;
data showing the minimum and maximum values for various characteristics of these
products are presented in Table 8. Clarification and gelation did not occur in
any of these products after storage at either 400F. for 48 hr. or 800F. for 24 hr.

Examination of the 500 Brix concentrates into which air was intentionally
whipped has given results which appear to indicate that "oxidized" off-flavors,
such as tallowy or castor oil, developed more rapidly in products made from Marsh


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718b 10/11/56 FWW







-4-


grapefruit than in those prepared from Duncan grapefruit; also that these flavor
defects occurred more rapidly when fruit that had been arsenated was used than
when the concentrates were made from unarsenated fruit, irrespective of the
variety of fruit used. It is believed that these indications should be confirmed
by repeating this study during another season before any final conclusions are
drawn.

Flavor evaluations, complete analyses, and critical examination of the data
already obtained from the study of the 80 concentrate packs involved in this
investigation have not yet been made and, therefore, relationships between fruit
maturity and the quality of the concentrates cannot be discussed at this time.






































Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718c 10/11/56 FWW








Table 1
Minimum, maximum, and average assay values for 28 samples of commercial
frozen concentrated grapefruit juices collected from 11 plants
during the 1955-56 season

Minimum Maximum Average
0 Brix 280C. 39.9 45.6 43.1

Acid as anhydrous citric % 3.89 4.66 4.28
Brix/acid ratio 8.9 11.2 10.1
Ascorbic acid
Concentrate mg./l0g. 96 149 120
Recon. juice % by vol. 29 44 36
Recoverable oil
Concentrate ml./100g. 0.006 0.044 0.022
Recon. juice % by vol. 0.002 0.013 0.007

Glycosides as naringin
Total mg./l00 ml. 36 64 50
Naringin mg./l00 ml. 20 41 31

Pectinesterase activity concentrate 0.3 3.4 1.3
(PE.u.)g. soluble solids X 1000

Pectin
Centrifuged juice mg./lOOg. 19.4 48.5 29.7

Pulp % by volume 4.0 11.5 6.0

Color Hunter Color Difference Meter
Concentrate "Rd" value 15.9 22.0 18.8
Concentrate "a" value -3.3 -6.7 -5.1
Concentrate "b" value 17.5 22.4 19.6

Reconstituted juice "Rd" value 13.7 20.1 15.6
Reconstituted juice "a" value -8.0 -9.4 -8.4
Reconstituted juice "b" value 7.4 12.2 9.4

Diacetyl value p.p.m. 0.0 1.0 0.2








Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718d 10/11/56 FWW










Table 2


Characteristics of raw juices extracted
from different lots of grapefruit for experimental
packs of frozen concentrated grapefruit juices.

Date Source of Variety- of Raw juice
processed fruit fruit -
Brix Acid Ratio I Pulp
_% by vol.
3/23/56 Florence Foods Seedy 13.9 1.67 8.3 15.0

3/27/56 Station-Plot R Seedy 13.6 1.73 7.8 22.0

3/28/56 Snively Groves Seedy 12.5 1.35 9.3 18.0

4/20/56 Station-Block 2 Seedless 9.1 1.26 7.2 5.0

4/24/56 Station-Plot R Seedy 13.8 1.55 8.9 8.5

4/25/56 Minute Laid Seedless 9.3 1.17 7.9 7.4

5/3/56 Station Seedless 9.4 0.90 10.4 5.0
East Coast
5/4/56 Station Seedless 9.1 1.11 8.2 5.0
East Coast
5/8/56 Pasco Seedy 12.7 1.41 9.0 11.0

5/9/56 Station-Plot R Seedy-505% 11.5 1.20 9.6 7.0
East Coast Seedless-50
7/2/56 Station- Seedy 11.5 1.44 8.0 8.0
Block 19 1 __


Florida Citrus Experiment Station and Florida Citrus Ccnmmission,
Lake Alfred, Florida. 718 e 10/11/56 FJF











Table 3
Minimum, maximum, and average assay values for 11 experimental packs
of unsweetened frozen concentrated grapefruit juices
Minimum Maximum Average
Brix 2800. 37.9 38.6 38.3

Acid as anhydrous citric % 3.82 5.33 4.55

Brix/acid ratio 7.1 10.1 8.5

Ascorbic acid
Concentrate mg./lOOg. 119 177 135
Recon. juice % by vol. 35 53 40

Recoverable oil
Concentrate ml./lOOg. trace 0.020 0.002
Recon. juice % by vol. trace 0.006 trace

Glycosides as naringin
Total mg./100 ml. 56 74 66
Naringin mg./l00 ml. 39 51 45

Pectinesterase activity concentrate 0.3 1.6 0.9
(PE.u.)g. soluble solids X 1000

Pectin
Centrifuged juice mg./.OOg. 28.5 53.7 36.3

Pulp % by volume 4.0 12.0 6.5

Color Hunter Color Difference Meter
Concentrate "Rd" value 15.2 18.7 16.9
Concentrate "a" value -5.7 -2.6 -4.9
Concentrate "b" value 17.5 20.0 18.7

Reconstituted juice "Rd" value 13.3 17.4 15.2
Reconstituted juice "a" value -8.8 -7.3 -8.4
Reconstituted juice "b" value 8.2 11.4 9.7








Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718f 10/11/56 Fi







Table 4


Flavor grades and acceptability of 11 experimental packs
of unsweetened frozen concentrated grapefruit juices.


Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 718g 10/11/56 FWW


Brix/Acid Number of different taste Percentage of total
Date ratio of panels designating the individual grades
Packed concentrate flavor grade indicated indicating that
product was acceptable

Unsweetened 38 Brix Concentrates

Good Fair Poor
3/23/56 8.2 5 1 70.7

3/27/56 7.8 4 2 62.8
3/28/56 9.3 3 2 70.3

4/20/56 7.1 5 1 58.5
4/24/56 8.8 2 4 79.1

4/25/56 7.9 4 2 51.2

5/3/56 10.1 2 3 77.4

5/4/56 7.9 4 1 62.2
5/8/56 9.1 6 76.7
5/9/56 9.6 2 4 83.7

7/2/56 7.9 4 2 53.5









Instructions to Taste Panel


Evaluation of Flavor of Frozen Concentrated Grapefruit Juices


Reconstituted frozen unsweetened or sweetened grapefruit con-
centrate. Three samples of commercial and/or experimental
products.


Directions:


(a) Please rinse mouth with water before tasting each
sample.

(b) Grade for flavor on the following basis and do not con-
sider other factors such as color or separation.


Excellent
Very good
Good
Fair


10
9
8-7
6-5


Poor
Very poor
Unpalatable


4-3
2
1


Use excellent, good, or fair only if the juice in your
opinion is acceptable as frozen grapefruit concentrate,
and therefore, would be repurchased by you.


(c) If you score a sample of juice 4 or lower, indicating
that the product is not acceptable as frozen grapefruit
concentrate, and therefore, would not be repurchased by
you, then indicate all of the flavor defects responsible
for the poor flavor quality.


Indicate flavor defects using only the
terms. If necessary, other terms will
list. If you are not sure of the type
any juice, which you score 4 or lower,
it is nondescript.


following descriptive
be added to this
of flavor defect in
then indicate that


Too sour (acid)
Too sweet
Too bitter
Too astringent


Flavor Defects

Excessive peel oil
Heated
Cardboard
Castor oil
Tallowy


Weak flavor
Immature fruit
Overmature fruit
Stale fruit


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
685 7/26/56 FWW


Samples:






Table 5


Flavor grades and acceptability of 11 experimental packs
of sweetened frozen concentrated grapefruit juices.


Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 718h 10/11/56 FIU


Brix/Acid Number of different taste Percentage of individual
Date ratio of panels designating the grades indicating that
Packed concentrate flavor gradeindicated product was acceptable


Concentrates Minimum sugar added
.\Good Good Fair Poor
3/23/56 10.1 1 .2 3 89.7

3/27/56 9.7 3 3 80.5

3/28/56 9.9 2 4 79.5
4/20/56 9.9 1 3 2 92.5
4/24/56 10.0 5 1 95.1
4/25/56 10.1 3 3 87.5

5/4/56 9.8 4 2 87.2
5/8/56 9.9 2 4 85.4
7/2/56 9.8 2 4 85.0





Table 6


Flavor grades and acceptability of 11 experimental
packs of sweetened frozen concentrated grapefruit
juices.


Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 718i 10/11/56 FWW


Brix/Acid Number of different taste Percentage of individual
Date ratio of panels designating the grades indicating that
packed concentrate flavor grade,indicated, product was acceptable


Concentrates viaximum sugar added

V, Good Good Fair Poor

3/23/56 11.7 1 2 3 87.2

/27/56 10.8 2 3 1 77.5

3/28/56 13.0 1 1 3 1 74.4

4/24/56 12.4 4 2 90.0

4/25/56 11.2 3 3 82.5

5/3/56 12.5 5 1 89.7

5/4/56 11.2 4 1 89.2
5/8/56 12.8 2 4 85.0

5/9/56 13.4 1 3 2 90.0

7/2/56 11.1 2 4 80.0






Table 7


Characteristics of experimental packs of frozen
concentrated grapefruit juices processed to
determine the effect of maturity of fruit on
the quality of the concentrates.


Florida Citrus Experirent Station
and Florida Citrus Commission,
Lake Alfred, Florida. 718j 10/11/56 FW


Date Variety of Fruit Concentrate
pc.cked fruit arsenated uBrix Acid Ratio

1/5/56 Duncan No 39.2 6.62 5.9
2/16/56 in 39.0 6.31 6.2
4/6/56 38.7 6.10 6.3
5/15/56 38.4 5.28 7.3
6/27/56 38.7 4.90 7.9
1/6/56 Duncan Yes 38.4 5.50 7.0
2/17/56 39.5 5.88 6.7
4/6/56 38.7 5.18 7.5
5/16/56 38.1 4.00 9.5
6/26/56 39.1 3.46 11.3

1/4/56 Marsh No 38.9 5.56 7.0
2/20/56 39.0 5.15 7.6
5/56 38.9 4.82 8.1
5/18/56 37.8 4.26 8.9
6/29/56 0 39.2 3.89 10.1

1/4/56 Marsh Yes 39.3 4.78 8.2
2/21/56 39.2 4.56 8.6
4/5/56 38.2 4.05 9.5
5/17/56 38.1 3.90 9.8
6/28/56 38.9 3.04 12.8











Table 8


Minimum, maximum, and average assay values for 20 experimental packs
of frozen concentrated grapefruit juices processed to determine
the effect of maturity of fruit on the quality of the concentrates

Minimum Maximum Average
oBrix 2800C. 37.8 39.5 38.8

Acid as anhydrous citric % 3.04 6.62 4.86

Brix/acid ratio 5.90 12.8 8.3

Ascorbic acid
Concentrate mg./lOOg. 95 153 134
Recon. juice % by vol. 28 45 40

Recoverable oil
Concentrate ml./lOOg. trace 0.081 0.015
Recon. juice % by vol. trace 0.002 0.001

Glycosides as naringin
Total mg./l00 ml. 66 102 80
Naringin mg./l00 ml. 42 62 52

Pectinesterase activity concentrate 0.2 2.1 1.1
(PE.u.)g. soluble solids X 1000

Pectin
Centrifuged juice mg./l0g. 23.9 55.6 40.6

Pulp % by volume 7.0 21.5 12.5

Color Hunter Color Difference Meter
Concentrate "Rd" value 15.6 20.1 18.4
Concentrate "a" value -6.5 -2.1 -4.7
Concentrate "bi value 18.2 20.3 19.5

Reconstituted juice "Rd" value 15.6 18.5 17.1
Reconstituted juice "a" value -9.1 -7.1 -8.5
Reconstituted juice "b" value 8.0 12.8 10.8

Diacetyl value p.p.m. 0.0 1.5 0.4




Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
718k 10/11/56 FWW




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