Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 57-5
Title: Stability of frozen concentrated orange juice with different levels of pectin and pectinesterase activity
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 Material Information
Title: Stability of frozen concentrated orange juice with different levels of pectin and pectinesterase activity
Series Title: Citrus Station mimeo report
Physical Description: 2 leaves : ; 28 cm.
Language: English
Creator: Rouse, A. H
Atkins, C. D
Moore, E. L
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
Subject: Frozen concentrated orange juice -- Storage -- Florida   ( lcsh )
Frozen concentrated orange juice -- Quality -- Florida   ( lcsh )
Pectin   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: A.H. Rouse, C.D. Atkins and E.L. Moore.
General Note: Caption title.
General Note: "October 11, 1956."
 Record Information
Bibliographic ID: UF00072382
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74906948

Full Text

Citrus Station Mimeo Report 57-5
October 11, 1956

Stability of Frozen Concentrated Orange Juices with Different Levels
of Pectin and Pectinesterase Activity
A. H. Rouse, C. D. Atkins and E. L. Moore

The purpose of this investigation was to demonstrate that pectin is a major
contributing factor to the storage life of frozen concentrated orange juice and
that the cloud stability of orange concentrate is largely due to the quantity of
pectin present, as well as to the pectinesterase activity. If this is true, then
a reasonably complete index of product stability could only be obtained by know-
ing the values of both of these factors. This study was undertaken to test the
effect of these two factors on the storage life of 420 Brix commercial orange
concentrates at a storage temperature of 400F. Cataphoretic experiments were
also determined on the water-soluble pectin, chromatophores, and the suspended
fine particles that disperse light in centrifuged orange juice.

Eight commercial packs of 420 Brix frozen concentrated orange juice were
selected from 215 packs that had been collected from 24 plants during the 1954-55
season. These eight packs were selected on the basis of pectin content and
pectinesterase activity (Table 1); the pectin and enzymic values chosen were based
upon analyses of the 215 commercial packs. A group of four packs were chosen
which contained a low content of pectin and four levels of pectinesterase activ-
ity; another group of four packs were picked which contained a high content of
pectin and had four similar levels of enzymic activity. The products selected
had approximately the same pH, 3.8-3.9; the initial cloud or turbidity in the
centrifuged reconstituted juices was also approximately the same, as indicated by
a range of 34.5 to 42.0% light transmittance.

For each of the eight samples, listed in Table 1, 15 cans with the same code
number from one of the selected commercial packs were removed from -80F. storage
and thawed for 1 hour on a rotary thawer at 400F. These cans of thawed concen-
trate were then immediately mixed to insure uniformity into a composite sample,
which was rapidly poured into 6-oz. cans; the cans were closed and placed at 400F.
storage. Samples of the eight concentrates were removed for analysis at periodic
intervals until extreme clarification had developed. Analyses of the samples
initially and during storage are tabulated in Table 1.

Samples 1, 3, 5, and 7 represent those products with high content of pectin
containing initially from 44.0 to 53.7 mg./lOOg. in the centrifuged juice, while
samples 2, 4, 6, and 8 are products with low pectin content from 27.2 to 31.0
mg./lOOg. The four levels of pectinesterase activity in each group were approxi-
mately 4, 8, 12, and 18 units. Thus, for comparison, samples 1 and 2 had similar
low activities, whereas the variation was in the quantity of pectin, 50.4 mg./lOOg.
in the former and 28.5 mg./lO0g. in the latter. Likewise, the pairs of samples
3 and 4, 5 and 6, and 7 and 8 were similar, except for the quantity of pectin,
which was high in the first sample and low in the second sample of each pair.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
707b 10/11/56 AHR

Intrinsic value of pectin in relation to the stability of commercial frozen concentrated
orange juices
Reconstituted juices
Storage Njoncentrifuged Centrifuged
Sample period Pulp b (PE.u.)g. Pectin Light Degree of
number at 400F. volume soluble solids as AGA transmittance-o clarification
days % X 103 mg./100g. Lumetron 402-E
I_ High pectin and low pectinesterase
Initial 12.5 3.8 50.4 38.0 None
35 18.0 3.6 34.9 50.5 None
1 49 24.0 3.4 24.6 62.5 Slight
53 22.0 3.3 16.2 81.0 Definite
56 22.0 3.8 12.3 87.0 Extreme
Low pectin and low pectinesterase___
Initial 6.5 4.0 28.5 40.0 None
7 10.0 3. 8 22.6 50.5 None
2 10 12.5 3.6 15.5 67.5 Slight
13 13.0 3.8 11.0 80.5 Definite
16 16,0 3.8 7.9 90.0 Extreme
_______ High pectin and average pectinesterase .
Initial 12.5 7.6 53.7 34.5 None
9 22.0 6.6 32.3 54.0 None
3 11 22.0 6.7 27.8 65.5 Slight
14 23.5 6.6 16.8 80.5 Definite
18 23.0 7.5 11.0 85.5 Extreme
Low pectin and average pectinesterase__
Initial .7.0 8.7 31.0 34.5 None
2 12.0 7.7 24.6 42.5 None
4 3.5 15.0 8.6 12.9 66.0 Slight
6 16.0 7.9 9.7 79.5 Definite
8 16.5 7.5 7.1 90.0 Extreme
After storage includes pulp and insoluble solids.

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TABLE 1 continued
Reconstituted juices
Storage Noncentrifuged I Centrifuged
Sample period Pulp by (PE.u.)g. Pectin Light Degree of
number at 400F. volume soluble solids as AGA transmittance-% clarification
days % X 103 mg./100g. Lumetron 402-E
High pectin and above average pectinesterase
Initial 11.0 11.0 49.8 35.5 None
9 19.0 11.7 34.3 47.5 None
5 12 22.0 11.4 23.9 61,0 Slight
14.5 22.5 11.0 18,8 72.0 Definite
15.5 22.0 : 11.0 9.1 92.5 Extreme
Low pectin and above average pectinesterase
Initial 6.5 12.5 29.1 40.0 None
2 11.5 10.7 21.3 52.5 None
6 3 14.0 11.3 16.8 62.5 Slight
5 15.0 11.7 9.7 78.5 Definite
7 14.5 10.4 6.5 88.5 Extreme
____ __High pectin and high pectinesterase
Initial 10.0 18.6 44.0 38.5 None
2 17.0 18.4 33.6 46.5 None
7 3 21.0 19.2 22.0 61.0 Slight
4 21.0 18.0 14.2 75.5 Definite
6 22.0 17.0 9.7 86.5 Extreme
Low pectin and high pectinesterase
Initial 7.0 18.3 27.2 42.0 None
1 12.0 18.6 19.4 57.0 None
8 1.5 12.5 20.6 14.9 66.5 Slight
2 13.5 19.3 10.4 78.0 Definite
3 13.5 18.2 6.5 89.0 Extreme

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
707a 9/21/56 AHR

After storage includes

pulp and insoluble solids.

Samples 1, 3, 5, and 7, containing a high content of pectin, retained a satis-
factory cloud after storage at 400F. for 50, 12, 14, and 3.5 days, respectively,
whereas samples 2, 4, 6, and 8 with low content of pectin retained a good cloud
for 10, 4, 3.5, and 1.5 days, respectively; these values were obtained from
curves that are not included in this report. The storage life of the orange
concentrates at 400F. was always greater in the samples with the high pectin con-
tent; also the duration of satisfactory cloud retention in the stored samples
decreased with increased pectinesterase activity, when the amount of pectin was
approximately the same.

All of the samples lost water-soluble pectin during storage at 400F., and
the conversion of this pectin to water-insoluble pectinates and pectates resulted
in an apparent increase in the pulp content during storage as shown in Table 1.

It was also observed that, as loss of cloud occurred in the concentrates
during storage, the color bodies or chromatophores were almost completely absent
in the centrifuged juices by the time definite clarification had taken place.

Cataphoretic experiments showed that both the water-soluble pectin and the
suspended fine white particles, which dispersed light in centrifuged orange
juice, migrated to the anode indicating negative charged particles; the chromato-
phores migrated to the cathode indicating a positive charge. Since like charges
on colloidal particles repel and opposite charges on particles attract each
other, it is inferred that coagulation and settling out of the suspended parti-
cles may be brought about by the attraction of the positive charged chromatophores
to the negative charged particles in the orange juice.

In summary, the results of this investigation showed that the stability, and
therefore the storage life, of 420 Brix frozen concentrated orange juice depends
upon both the amount of pectin and the pectinesterase activity in the product.
In general and not considering some other factors that may be involved, orange
concentrates that have a high pectin content and a low enzymic activity will be
the most stable, whereas the least stable products will be those with a low pectin
content and a high pectinesterase activity.

Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
707c 10/11/56 AHR

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