Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 54-5
Title: Preliminary study on relationship of pectic substances in citrus concentrates to clarification and gelation
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Permanent Link: http://ufdc.ufl.edu/UF00072352/00001
 Material Information
Title: Preliminary study on relationship of pectic substances in citrus concentrates to clarification and gelation
Series Title: Citrus Station mimeo report
Physical Description: 4 leaves : ; 28 cm.
Language: English
Creator: Rouse, A. H
Atkins, C. D
Huggart, R. L
Citrus Experiment Station (Lake Alfred, Fla.)
Florida Citrus Commission
American Can Company
Publisher: Florida Citrus Experiment Station :
Florida Citrus Commission
Place of Publication: Lake Alfred FL
Publication Date: 1954
 Subjects
Subject: Citrus juices -- Composition -- Florida   ( lcsh )
Pectin -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: A.H. Rouse, C.D. Atkins, and R.L. Huggart.
General Note: Caption title.
General Note: "American Can Company cooperating through the establishment of a grant-in-aid."
 Record Information
Bibliographic ID: UF00072352
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74145699

Full Text


Preliminary Study on Relationship of Pectic Substances in Citrus
Concentrates to Clarification and Gelation*
A. H. Rouse, C, D. Atkins, and R. L. Huggart

A study was begun to correlate the pectic substances and related factors,
such a.s pH and peotinestbrase activity, with "cloud" stability and gelation in
citrus juices and concentrates. This preliminary report contains data concerned
with the quantitative amount of pectin in the initial 420Brix concentrates which
results in-various degrees"of gelation when the concentrates are subjected to a
temperature of 80F. for 24 hours.

Pineapple orange and Duncan grapefruit concentrates were prepared from juices
ranging from 2 to 26% pulp content by volume, concentrated to 42OBrix, and placed
in -8oF. storage. These juices received no heat treatment before or after concen-
tration.

Juice, pulp, and seeds were extracted from the fruit using a Citro-Mat extrac-
tor and then passed through a Food Machinery finisher using a 0.030 inch screen.
This juice was again screened through a 165 mesh shaker screen and was called the
base juice, The juice, seeds, and pulp extruded from the finisher were again fin-
ished with a 0.030 inch screen in order to prepare the pulpy juice. Finally both
juices were blended together to make single-strength juice with various pulp con-
tents by volume. The Pineapple juice had a pH 3.8, whereas the Duncan juice had a
pH 3.4.
Data showing pectinesterase activity, water and oxalate-soluble pectin, and
clarification initially and after short-term storage for 420Brix Pineapple orange
and Duncan grapefruit concentrates are presented in Tables 1 and 2, respectively.
Also presented is the degree of gelation for each sample after 24 hours storage at
80OF. From the data in Table 2, it can be shown that the sum of the water and
oxalate-soluble pectin in 420Brix Duncan concentrates increased after-short-term
storage. This indicated that there was some hydrolysis of protopect IiiatpH 3,4.
However, any slight change of the combined water and oxalate-soluble pectin in':
42gBrix Pineapple concentrates, Table 1, after short-term stort eell with -the
10% experimental error of the method.

Table 3 is a summary presenting the sum of the water and o Cat-soluble pec-
tin in the two series of concentrates together with their respe t -i degrees of /
gelation ranging from none to solid gels. Further evidence of pc3ti-correlation
with gelation has been obtained by the authors in processing and shrt-term storage
of 42Brix concentrates during a maturity study on Pineapple oranges. This evi .'
dence agreed very closely with that presented in Table 3 for the 42Brix Pineapple
orange concentrates. When the pectin concentration of the 42OBrix Duncan concen-
trates amounted to 0.3% or greater, solid gels were formed, whereas similar pectin
concentration in 42Brix Pineapple concentrates resulted in semi-gels. This dif-
ference may be the result of several factors, one of which may be pH. The Duncan
juice before concentration was pH 3.4, while the Pineapple juice was pH 3.8.

Arbitrary limits are presented in Table 4 showing concentration of pectin in
a 42OBrix concentrate that will result in various degrees of gelation. Pectin
concentration is only one of several factors necessary for solid gel formation.
Other factors are pH, methoxyl content of the pectinic acid, calcium ion concen-
tration, and soluble solids.
American Can Company cooperating through the establishment of a grant-in-aid.
Citrus Station Mimeo Report 54-5, Florida Citrus Experiment Station and Florida
Citrus Commission, Lake Alfred, Florida. 473 10/6/53 AHR










TABLE 1
Water and oxalate-soluble pectic substances, clarification, and gelation in Pineapple
orange concentrates

pulpa /42OBrix concentrate initial 420Brix concentrate after 24 hr. storage at 800F.
by (PE.u.)g. Pectin as AGAb Degree (FE.u,)g. Pectin as AGAb Degree Degree
vol. cone; per 100 g. cone. of cone, per 100 g. cone. of of
x 104 H20 (NH4)2C204 clarificationc x 104 H20 (NH4)2C204 clarificationCe i;gationd
% soluble soluble soluble soluble
g. g. g. g.

4 21 0.020 0.049 53-none 18 0.015 0.052 62-slight 0-none
7 111 0.040 0.096 50-none 100 0.017 0.128 94-extreme 1-very slight
10 161 0.031 0.155 53-none 150 0.021 0.184 97-extreme 2-slight
13 233 0.031 0.216 50-none 210 0.025 0.235 94-extreme 3-semi-gel
16 321 0.054 0.228 62-slight 315 0.032 0.288 94-extreme 3-semi-gel
19 379 0.048 0.289 61-slight 330 0.030 0.329 93-extreme 3-semi-gel
22 464 0.055 0.323 71-definite 384 0.035 0.362 96-extreme 3-semi-gel
26 529 0.068 0.353 70-definite 466 0.032 0.421 96-extreme 3-semi-gel


a Pulp content of juices before concentration.
b Anhydrogalacturonic acid (AGA).
c Clarification measured by percentage light transmission of centrifuged reconstituted juice using
lar cell in Lumetron colorimeter with filter No. 730. Degree of clarification: 0 59% = none;
70 84% = definite; 85-- 100% = extreme.
d Gelation: 0 = none; 1 = very slight; 2 = slight; 3 = semi-gel; 4 = solid gel.

Citrus Station Mimeo Report 54-5. Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 473a'- 10/6/53 AHR


10 mm. rectangu-
60 69% = slight;










TABLE 2
Water and oxalate-soluble pectic substances, clarification, and gelation in Duncan
grapefruit concentrates

pulpe 42oBrix concentrate initial h42Brix concentrate after 24 hr. storage at 800F.
by (PE.u.)g. Pectin as AGA Degree (PE.u.)g. Pectin as AGIF Degree Degree
vol. cone. per 100g. conc. of cone. per 100 g. cone. of of
% x 104 H20 (NH4)2C204 clarification x 104 H20 (NH4)20204 clarification gelationh
soluble soluble soluble soluble
g. g. g. g.
2,0 8 0.100 0.015 62-none 5 0.035 0.074 94-extreme 1-very slight
6.0 36 0.102 0.083 65-none 21 0.023 0.169 96-extreme 2-slight
8.5 54 0.102 0.139 77-slight 22 0.032 0.218 97-extreme 3-semi-gel
12.0 75 0.120 0.180 83-definite 27 0.034 0.274 96-extreme 4-solid gel
14.5 93 0.072 0.252 89-definite 35 0.042 0.335 98-extreme .4-solid gel
17.0 104 0.059 0.337 86-definite 45 0.042 0.396 96-extreme 4-solid gel
20.0 110 0.058 0.375 88-definite 55 0.049 0.449 96-extreme 4-solid gel
23.0 112 0.060 0.408 90-extreme 56 0.036 0.493 95-extreme 4-solid gel
e Pulp content of juice before concentration,
f Anhydrogalacturonic acid (AGA).
g Clarification measured by percentage light transmission of centrifuged reconstituted juice using 10 am. rectangular
cell in Lumetron colorimeter with filter No. 730. Degree of clarification: 0 69% = none; 70 79% = slight;
80 89% = definite; 90 100% = extreme.
h Gelation: 0 = none; 1 = very slight; 2 = slight; 3 = semi-gel; 4 = solid gel.
Citrus Station Mimeo Report 54-5. Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 473b 10/6/53 AHR









TABLE 3
Relationship of pectin concentration to degree of gelation in citrus concentrates

42oBrix Pineapple orange concentrates 42OBrix Duncan grapefruit concentrates
Water and oxalate- Degree of gelation Water and oxalate- Degree of gelation
soluble pectin after 24 hr. at 800F, soluble pectin after 24 hr. at 80F.

0.069 none 0.115 very slight
0.136 very slight 0.185 slight
0.186 slight 0.241 semi-gel
0.247 semi-gel 0.300 solid gel
0.282 semi-gel 0.324 solid gel
0.337 semi-gel 0.396 solid gel
0.378 semi-gel 0.433 solid gel
0,421 semi-gel 0.468 solid gel


TABLE 4
Tentative limits of combined water and oxalate-soluble pectin in the initial 42oBrix
concentrate necessary to form the various degrees of gelation when the concentrate
is stored at 800F. for 24 hours

Pectin per 100 grams cone. Degree of gelatin
(0.170 none or 'ery slight
0.170 to 0.220 slight
0.220 to 0.280 semi-gel
>0.280 semi-gel or solid geli
i A pH 3.4 or lower favors the formation of a solid gel.
Citrus Station Mimeo Report 54-5. Florida Citrus Experiment Station and Florida
Citrus Commission, Lake Alfred, Florida. 473c 10/6/53 AHR




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