Group Title: Citrus Station mimeo report - Florida Citrus Experiment Station ; 60-4
Title: Characteristics of pectins isolated from orange and grapefruit concentrates
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Permanent Link: http://ufdc.ufl.edu/UF00072395/00001
 Material Information
Title: Characteristics of pectins isolated from orange and grapefruit concentrates
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: 1959
 Subjects
Subject: Pectin -- Analysis -- Florida   ( lcsh )
Orange juice -- Composition -- Florida   ( lcsh )
Grapefruit juice -- Composition -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: A.H. Rouse, C.D Atkins and E.L. Moore.
General Note: Caption title.
General Note: "September 16, 1959."
 Record Information
Bibliographic ID: UF00072395
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 74844167

Full Text


Citrus Station Mimeo Report 60-4
September 16, 1959

Characteristics of Pectins Isolated from Orange and
Grapefruit Concentrates

A. H. Rouse, C. D. Atkins and E. L. Moore

Pectic substances play an important role in the stabilization and
characterization of processed citrus products and further information concerning
the pectins and pectic enzymes is desirable. "Cloud" or turbidity in orange and
grapefruit juices and firmness of processed citrus sections are desirable physi-
cal characteristics indicative of good quality products. Pectin is the naturally
occurring colloidal stabilizer that gives citrus juice viscosity or consistency,
termed "body" by the fruit industry. When water-soluble pectin is degraded or
altered by enzymic activity, the juice clarifies and becomes "watery" because of
the settling of the colloidal suspended material as well as a rapid separation
of the suspended water-insoluble solids. Concentrates prepared from seedy
varieties of citrus are generally less stabilized than those prepared from less
seedy varieties primarily because of a difference in pectin quality rather than
quantity.

A fundamental study was begun this past year to increase our knowledge of
the pectic enzymes and the role of pectin or related compounds so as to better
understand "cloud" mechanism in processed citrus concentrates. Pectins were
isolated, as alcohol-insoluble solids (AIS), from 2 commercial packs of frozen
orange concentrate, one having a high and the other a low water-soluble pectic
content, and 1 commercial pack of frozen grapefruit concentrate; also, from an
experimental pack of frozen orange concentrate prepared from Pineapple oranges
which had been extremely damaged by cold weather. The quantity of serum pectin
found in these 4 concentrates was 210, 105, 158 and 350 mg./lO g. concentrate,
respectively.

The pectic substances from each of the 4 AIS were divided into 3 fractions
by successive extractions with distilled water, ammonium oxalate and hydrochloric
acid. The centrifuged liquor of each extract was poured into several volumes of
isopropyl alcohol and the precipitated substance was vacuum dried. The purity
of these 12 alcohol precipitates, as pectins, was determined on the basis of
their anhydrogalacturonic acid (AGA) content (Table 1) and was generally low
ranging from 19.0 to 31.5% for the water-soluble, 17.5 to 37.0% for the ammonium
oxalate-soluble and 33.0 to 41.0% for the hydrochloric acid-soluble. Methoxyl
contents of the pectic fractions (Table 1) varied from 5.5 to 10.2% for the
4ater extracts, from 3.1 to 8.9% for the oxalate extracts and from 8.9 to 10.8%
For the acid extracts.

Other data on the alcohol precipitates of the water-soluble pectic fractions,
from the AIS obtained from the 4 concentrates, are presented in Table 2 pertain-
ing to jelly grade, protein, higher carbohydrates and ash. Jelly grades were
estimated by preparing standard jellies and measuring the jelly strength on a
Tarr-Baker Jelly Strength Tester. Grades for the water-soluble pectins, indica-
tive of molecular polymerization, were 89, 0, 107 and 92, respectively, for the
2 commercial orange packs, the commercial grapefruit pack and the experimental
Pineapple orange pack prepared from freeze-damaged fruit. Highest jelly grade


Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
928 9/16/59 AHR






-2-


was obtained from the grapefruit pectin, whereas the pectin from the commercial
orange concentrate with low pectic content did not form a jelly.

Crude protein is reported as nitrogen multiplied by the factor 6.25. The
alcohol precipitates were sufficiently leached so that neither original reducing
nor inverted sugars were found in the water-soluble extracts. Boiling acid hy-
drolysis showed the presence of higher carbohydrates, other than pectin and
determined as invert sugar, in the precipitates from the commercial orange con-
centrate with high pectic content and from the experimental Pineapple orange
concentrate; insufficient samples of the water-soluble alcohol precipitates from
the other 2 concentrates prevented this analysis. Total ash was found to be
highest in the water-soluble fraction ranging from 5.7 to 7.7% and much less in
the other 2 fractions where it ranged from 0.6 to 1.7%. Also presented in Table
2 under ash constituents are the ammonium hydroxide precipitates which after
ignition are commonly known as R203. These combined oxides are primarily of
aluminum, iron, titanium, zirconium and phosphorus. The percentage of R203 was
many times greater in the precipitates of the water-soluble extracts from the
commercial orange concentrate with low pectic content and from the commercial
grapefruit concentrate than in the other 2 packs; however, calcium content was
greater in the precipitates from the orange concentrates having a high pectic
content and made from frozen fruit than in the other 2 products which had shown
the higher R203.

Pectins from juices and concentrates with other distinguishing characteris-
tics will be isolated and analyzed as well as related compounds, such as cellu-
lose. Also, plans are to further study the mechanism by which water-soluble
pectin in citrus juices and in insoluble solids is converted to a lower degree
of methoxylation and jelly grade.























Florida Citrus Experiment Station
and Florida Citrus Commission,
Lake Alfred, Florida.
928 a 9/16/59 AHR






Table 1. Methoxyl content and purity of the alcohol precipitates
from the alcohol-insoluble solids of citrus concentrates


of the pectic fractions extracted


Purity of pectin as AGAI soluble in Methoxyl content of pectin soluble in
Type of Ammonium Hydrochloric Ammonium Hydrochloric
citrus Water oxalate acid Water oxalate acid
concentrate % % % % % %
Commercial orange
with high pectic content 25.0 29.0 41.0 8.1 3.1 10.8
Commercial orange
with low pectic content 19.0 33.5 33.0 5.5 5.6 8.9
Commercial
grapefruit 31.5 37.0 39.5 9.2 8.9 10.3
Experimental Pineapple
orange from frozen fruit 25.5 17.5 41.0 10.2 3.7 10.6

SPectin expressed as anhydrogalacturonic acid (AGA).


Table 2. Analyses on the alcohol precipitates of the water-soluble pectic fractions extracted from the
alcohol-insoluble solids of citrus concentrates
Type of Pectin Protein Higher carbohydrates Total Ash constituents
citrus Jelly as AGA (N X 6.25) as invert sugar ash R203 Ca Mg
concentrate grade % % % % % % %
Commercial orange
with high pectic content 89 25.0 36.1 23.4 5.70 0.06 1.10 0.10
Commercial orange
with low pectic content 0 19.0 23.7 7.57 2.64 0.55 0.20
Commercial
grapefruit 107 31.5 24.5 7.70 2.92 0.78 0.21
Experimental Pineapple
orange from frozen fruit 92 25.5 26.1 27.1 6.28 0.08 1.10 0.15

Florida Citrus Experiment Station and Florida Citrus Commission,
Lake Alfred, Florida. 928 b 9/16/59 AHR




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