Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 60-8
Title: Preliminary report on rapid method for predicting physical stability of frozen orange concentrate
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 Material Information
Title: Preliminary report on rapid method for predicting physical stability of frozen orange concentrate
Series Title: Citrus Station mimeo report
Physical Description: 4, 4 leaves : ; 28 cm.
Language: English
Creator: Li, Kuang C
Ezell, George H
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: 1959
 Subjects
Subject: Frozen concentrated orange juice -- Quality -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Kuange C. Li and George H. Ezell.
General Note: Caption title.
General Note: "September 16, 1959."
 Record Information
Bibliographic ID: UF00072399
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74838238

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Citrus Station Mimeo Report 60-8
September 16, 1959
Preliminary Report on Rapid Method for Predicting Physical Stability
of Frozen Orange Concentratel

Kuang C. Li and George H. Ezell


When clarification and gelation occur in frozen orange concentrate during
distribution and storage, the quality of the product is lowered and it becomes
less acceptable to consumers. Conventional tests to determine the physical
stability of this product after it is produced usually necessitate its storage
at 400F. for several days to a week. For quality control purposes, there is an
urgent need, therefore, to develop a rapid method for predicting the stability
of frozen orange concentrate to be used during continuous production in commercial
plants prior to filling of the product into cans for freezing. This investigation
was instigated to develop one or several rapid and reliable methods for determin-
ing the stability of frozen orange concentrate, including its tendency to both
clarify and gel. The principal purpose of this report is to describe and discuss
a rapid method that has been developed for predicting only the cloud stability in
420 Brix frozen orange concentrate, so that it might be checked for reliability,
along with conventional methods, during the 1959-60 citrus season in the quality
control laboratories of some commercial concentrate plants.


Experimental Procedures and Results
Development of Rapid Method for Determining Cloud Stability. Since the
action of pectinesterase on the pectin in orange concentrate is one of the major
causative factors involved in the loss of cloud or clarification in this product,
it was decided to determine if a rapid method could be developed by increasing
the rate of this enzymic reaction through variations in pH, temperature and time,
using either concentrate or reconstituted juice. Preliminary attempts to clarify
reconstituted juices at the optimum pH 7.5 of orange pectinesterase did not re-
sult in visual or measurable clarification, even after holding at room temperature
for many hours, whereas, clarification occurred in some of the control juices in
which the pH was not adjusted. It was later found in this laboratory that if the
pH of these juices, after holding for some time at pH 7.5, was readjusted to
within the pH range of orange juice, then the loss of cloud in the less stable
juices was readily noticeable. These observations provided the basis for a
possible procedure for a rapid test. The conditions of pH, temperature and time
of reaction were then investigated, so that results could be obtained as rapidly
as possible and also be in agreement with those found using a conventional method,
such as storage of the orange concentrate for 96 hr. at 400F. Commercial 420 Brix
frozen orange concentrate, packed in 6-oz. cans, was used for this study. The
concentrate was thawed undisturbed in running tap water of approximately 800F. for
30 minutes.

Description of Rapid Method for Determining Cloud Stability. Unfrozen
orange concentrate is reconstituted with 3 volumes of distilled or deionized
water. Then the pH of 100 ml. of the reconstituted juice is adjusted as rapidly
as possible to exactly 7.5 or other predetermined, desirable pH, using a pH meter
and adding 4N NaOH while the juice is rapidly stirred mechanically with a glass

1 Cooperative research by Florida Citrus Experiment Station and Florida Citrus
Commission, aided by a grant-in-aid from the Continental Can Company.
Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida. 939 d 9/16/59 KCL





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stirrer. The temperature of the juice should be at 800 + loF. when the necessary
amount of 4N NaOH has been added and kept at this temperature for exactly 10
minutes. The reaction time is measured by starting a stopwatch as soon as the
desired pH is reached, as indicated by the pH meter. The mixture is constantly
stirred but without further adjustment of pH. After exactly 10 minutes, 50 ml.
of the reacted mixture is immediately pipetted into a beaker containing 2.7 ml.
of glacial acetic acid and then well mixed to stop the enzymic reaction and at
the same time obtain a mixture having a pH in the range of that of orange juice.
The mixture is then centrifuged and the cloud or turbidity in the supernatant
liquid determined in the usual manner as percentage light transmittance using a
colorimeter. In this study the mixture was centrifuged for 10 minutes at 1400
r.p.m. in an International Centrifuge, Size 1, Type SBV. The colorimeter used
was a 402-E Lumetron with 730 filter and 10 mm. cell.

Data presented in Table 1 for four samples of commercial frozen orange con-
centrate show that to obtain reproducible and reliable results the reaction
conditions of pH, temperature and time, as described above, for the rapid method
must be carefully controlled. There was practically no difference in the degree
of clarification indicated by the rapid method when the concentration of the
NaOH was 4 0.4N or the quantity of glacial acetic acid used was 2.7 + 0.2 ml.

Determination of Cloud Stability in Samples of Commercial Frozen Orange
Concentrate using Rapid Method. During the 1958-59 citrus season, 197 commercial
samples of frozen orange concentrate were collected from 23 Florida plants, so
that 17 characteristics of these products could be determined (See Citrus Station
Mimeo Report 60-9, which follows this report). These samples were examined for
cloud stability by the rapid method and results compared with those obtained
after storage of these products for 96 hr. at 400F. and also 24 hr. at 800F. Data
obtained are summarized and shown in Table 2. When the rapid method was used with
reaction conditions of pH 7.5, 800F. and 10 minutes, the correlation of the re-
sults, indicating the degree of clarification, was 87% when compared with those
obtained after storage of the samples for 96 hr. at 400F. Since better correlation
was necessary for the rapid method to be of practical value, the samples were
checked again by this method using the same temperature and time, but adjusting
the initial reaction pH to 6.5 instead of 7.5. Results showed 96% correlation
with those after storage for 96 hr. at 40OF.

Data are presented in Table 3 on an individual or single sample basis for
28 samples of orange concentrate collected from 8 of the 23 commercial plants,
which gave different results when the rapid method and storage for 96 hr. at
400F. were both used to determine cloud stability. Twenty-six of these samples
gave different results using the rapid method with pH 7.5 and samples 20 and 22
were in agreement with the conventional procedure; however, similar results for
these 2 samples were not obtained by the two methods when pH 6.5 was used in the
rapid method.

It is seen from the information in Table 4 that 100% correlation was found
when 138 samples from 15 plants were examined for cloud stability by the rapid
method and after storage for 96 hr. at 400F.; this was true when using a pH of
either 6.5 or 7.5 in the rapid method. Also, on an individual plant basis the
correlation between the conventional and rapid method, pH 6.5, ranged from 57 to

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
939 e 9/16/59 KCL





-3-


100%, except for one plant from which only a single sample was obtained; when pH
7.5 was used in the rapid method, the range of agreement was 11 to 100l, not in-
cluding plant 8.

Data are also presented in Tables 3 and 4 showing the exact or maximum pH
value which was found to be necessary in the rapid method to obtain on either a
single sample or on all of the samples from each plant the best possible corre-
lation between the rapid and conventional methods. Only samples 1 and 21 gave
results which did not agree regardless of the pH used; however, correlation was
obtained when pH 7.5 and a reaction time of 11 or 15 minutes, respectively, were
tried. As shown in Table 4, the cloud stability of the samples on an individual
plant basis for all of the 23 plants, except plants 1 and 6, was found by the
rapid method, using a range of pH from 6.3 to 7.5, to be the same as that when the
samples were stored for 96 hr. at 40F.


Discussion of Results

A rapid method has been developed and described for determining the cloud
stability of orange concentrate. The method is primarily dependent upon adjust-
ing the pH of reconstituted juice, for example to pH 7.5, so that the rate of
reaction of pectinesterase on the pectin in the juice will be increased to such
an extent that the degree of clarification resulting in a short time at a specific
temperature will be equivalent to that which occurs when 42 Brix concentrate is
stored for 96 hr. at 400F. The degree of clarification or loss of cloud is
measured at the end of the time period in the usual manner in the centrifuged
reconstituted product, after the pH has been readjusted to within the range of
pH for orange juices.

When the major factors involved in the clarification of orange juice, such
as pectinesterase activity and the quantity and quality or grade of pectin, are
considered together with the many conditions which affect these factors, it is
remarkable that the experimental data show that when the conditions for the rapid
test of pH 6.5, 10 minutes and 800F. were used, 96% correlation was possible
between results from the rapid method and the conventional procedure based upon
the testing of 197 samples of commercial frozen orange concentrate. It should
again be emphasized that in using this rapid method, the conditions of pH. tempera-
ture and time must be carefullyand accurately controlled if reproducible and re-
liable data are to be obtained.

Throughout this investigation the problem of gelation in orange concentrate
has been continually considered and studied since a rapid method is also needed
to determine the possibility of gel formation in this product during storage and
distribution. Examination of the 197 samples of concentrate after storage for
24 hr. at 800F. showed that 67 or 34% had gelled to a very slight or slight ex-
tent (No. 1 or No. 2 gels), none of which was considered to be of significance
to consumers, and that semi-gels (No. 3 gel) were found in only 3 samples or
1.5%. No relationship of any practical importance was found between the degree
of gelation in the 197 samples and the degree of clarification, as determined by
the rapid method. This was expected since it is known that orange concentrate
will gel to some extent without clarification occurring to any practical amount.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
939 f 9/16/59 KCL









However, it was found and should be mentioned that of the 70 samples in which
some gelatin was noted 33 samples showed extreme clarification as indicated by
the rapid method using reaction conditions of pH 7.5, 800F. and 15 minutes; 28 of
these samples were those listed in Table 3. Also, 2 samples which did not gel
after storage for 24 hr. at 800F. clarified extremely when checked by the rapid
method with the above conditions.

On the basis of the data in this report it is suggested that during the
1959-60 citrus season the rapid method be tried in quality control laboratories
of concentrate plants, along with the conventional methods used by individual
plants for measuring cloud stability. By so doing comparable data may be obtained
to determine the reliability of the rapid method and find out if it is suitable
for quality control during the continuous production of commercial orange concen-
trate. Samples could be taken prior to filling in cans and freezing. As previous-
ly pointed out pH conditions for the rapid method will have to be established for
each plant so that maximum agreement between the current plant procedure and the
rapid method may be obtained. Temperature conditions other than 800F. may also
be used if necessary. Because of variations in some characteristics of orange
concentrate caused by various factors, such as different processing procedures,
it is impossible at this time to indicate one set of reaction conditions for the
rapid method that will be satisfactory for all plants; also, the opinion of
personnel concerning the amount of cloud stability desirable in concentrate varies
from plant to plant and such opinion also determines the conditions used for the
control of this characteristic.

This investigation will continue at the Station during the 1959-60 citrus
season, with emphasis being placed upon the development of a rapid method for
predicting the gelation potential in orange concentrate.





















Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
939 g 9/16/59 KCL









Table 1. Effect of variations in pH, temperature and time of reaction on
degree of clarification in commercial samples of frozen orange concentrate as
determined by rapid method
Conditions for Degree of clarification1
rapid method indicated by rapid method
pH Temperature Time Sample Sample Sample Sample
OF. minutes A B C D

6.4 800 10 44-none -- 35-none
6.5 71-definite 57-none -35-none
6.8 i" t 81-definite 70-definite 55-none 35-none
7.0 85-extreme 76-definite 60-slight 35-none
7.5 95-extreme 81-definite 67-slight 35-none
8.0 11 t" 92-extreme 78-definite 59-none 35-none

7.5 650 10 47-none 35-none
72 73-definite 43-none -35-none
76 76-definite 64-slight 35-none
78 88-extreme 75-definite 53-none 35-none
"79 78-definite 61-slight 35-none
80 95-extreme 81-definite 67-slight 35-none
81 83-definite 69-slight 35-none
82 85-extreme 73-definite 35-none
"86 97-extreme 90-extreme 80-definite 35-none

7.5 800 6 56-none - 35-none
" 7 68-slight 49-none 35-none
" 8 83-definite 73-definite 35-none
" 9 89-extreme 77-definite 59-none 35-none
" 10 95-extreme 81-definite 67-slight 35-none
" 11 87-extreme 73-definite 35-none
15 98-extreme 98-extreme 93-extreme 35-none
1
Degree of clarification determined as percentage light transmittance of
centrifuged reconstituted juice using Lumetron 402-E with 730 filter and
10 mm. cell. None = 0-59%; Slight = 60-69%; Definite = 70-84%; and
Extreme = 85-100%.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.













Table 2.
clarification
determined by


Comparison of frequency distribution tables for degree of
5n 197 commercial samples of frozen orange concentrate as
rapid and conventional methods


Rapid method
Group After 96 hr. 10 minutes at 800F, After 24 hr.
number1 at 40op.2 pH = 6.5 pH = 7.5 at 80F.2

Number of samples and degree of clarification3
190-none 186-none 167-none 160-none
1 1-slight 4-slight 10-slight
2-definite 6-definite 9--definite
1-extreme 13-extreme 11-extreme

2 2-slight 1-none 1-slight
2-none 1-slight 1-extreme

3 2-definite 1-none 1-definite
1-definite 1-extreme 2-extreme


4 3-extreme 1-none l-definite 3-extreme
2-extreme 2-extreme
1
Samples in each group were the same.
2 Data obtained by M. D. Maraulja.


See footnote 1 on Table 1.


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
939 a 9/16/59 KCL





Table
predicting


3. Comparison of results
the cloud stability of 28


using rapid method with different pH values for
commercial samplesI of frozen orange concentrate


Degree of clarification2
Plant Sample After 96 hr. Rapid method 10 minutes at 800F.
number number at 400F.3 pH = 7.5 pH = 6.5 pH for correlation with
96 hr. at 400F.
1 1 100-extreme 75-definite 48-none 7.5 for 15 minutes
2 56-none 69-slight 38-ino3ne 6. -.maximum
2 3 50-none 60-slight 38-none 7.0-maximum
1 4 53-none 93-extreme 53-none 6.5--maximum
5 55-none 92-extreme 46-none 6.5-maximum
"6 40-none 87-extreme 41-none 6.5-maximum
U 7 39-none 74-definite 37--none 6.6-maximum
it 8 45-none 92-extreme 89-extreme 6.3-maximum
9 56-none 95-extreme 71-definite 6.4-maximum
t .10 44-none 96-extreme 59-none 6.5-naximum
3 11 38-none 62-slight 40-none 7.4-maximum
4 12 38-none 94-extreme 59-none 6.5-maximum
13 38-none 81-defnite 38-none 6.6-maximEum
n 14 72-definite 92-extreme 71-definite 6.5 to 6.9
5 15 52-none 78-definite 37-none 6.8-maxmaum
16 55-none 92-extreme 50-none 6.6-maximum
S17 47-none 100-extreme 71-definite 6.3-maximum
18 49-none 98-extreme 50-none 6.6-maximum
19 45-none 98-extreme 59-none 6.5-maximum
6 20 67-slight 67-slight 40-none 7.0 to 7.5
21 64-slight 55-none 38-none 7.5 for 11 minutes
22 81-definite 81-definite 57-none 6.8 to 7.5
23 36-none 70-definite 46-none 6.6-maximum
24 40-none 81-definite 41-none 6.6-maximum
25 41-none 68-slight 4 5-rnone 6.9--:Laimum
7 26 53-none 79-definite /4U--none 6.5-.aivAhaum
_" 27 47-none 95-extreme 50-none_ 6.6--maximum
8 28 58-none 100-extreme 69- s8i ht 6. 4-ma xunum
1 Degree of clarification in 26 of these samples, determined using the rapid method with pH 7.5,
did not correlate with that obtained after storage for 96 hr. at 400F.; when pH 6.5 was used
in the rapid method, results by both methods agreed, except for 8 samples.
2 See footnote 1 on Table 1. 3 Data obtained by M. D. Maraulja.


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Table 4. Correlation on individual plant basis between results using rapid method and storage of samples
for 96 hr. at 400F. for predicting the cloud stability of 197 commercial samples of frozen orange concentrate
Total Rapid method 10 minutes at 800F.
Plant number of pH Correlation pH Correlation For best correlation
number samples Number of % Number of % pH Number of %
samples samples____ samples
1 11 7.5 9 82 6.5 10 91 6.9-exact 10 91
2 9 1 11 7 78 6.3-maximum 9 100
3 9 8 89 9 100 7.4-maximum 9 100
4 8 5 62 8 100 6.5-exact 8 100
5 8 3 37 7 87 6.3-maximum 8 100
6 7 3 43 4 57 6.8-exact 5 71
7 6 n 4 66 6 100 6.5-exact 6 100
8 1 0 0 0 0 6.4-maximum 1 100
9 to 23 138 138 100 138 100 6.5 to 7.5 138 100


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
939 c 9/16/59 KCL




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