Composition, structure, and physicochemical properties of field pea (Pisum sativum L.) starch

Ratnayake, R. M. Wajira Srinanda (2000) Composition, structure, and physicochemical properties of field pea (Pisum sativum L.) starch. Masters thesis, Memorial University of Newfoundland.

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Abstract

Starch from four cultivars (Carneval, Carrera, Grande and Keoma) of field pea (Pisum sativum L.) was isolated and its composition, structure, and physicochemical properties were investigated. The results obtained were compared with those of other legume starches reported in the literature. The yield of starch was in the range 32.7-33.5% on a whole seed basis. The starch granules were round to elliptical with smooth surfaces. The free lipid was 0.05% in all starches. However, bound and total lipids ranged from 0.24-0.29% and from 0.28-0.34%, respectively. The total amylose content ranged from 48.8-49.6%, of which 10.9-12.3% was complexed by native lipid. The degree of polymerization (DP) of isolated field pea amyloses ranged from 1300-1350. The chain length distributions of debranched amylopectins of the four starches were analyzed using high performance anion exchange chromatography equipped with a post-column amyloglucosidase reactor and a pulsed amperometric detector (HPAEC-ENZ-PAD). The proportion of short branch chains of chain length DP 6-12 ranged from 16.2-18.6%. Keoma displayed a larger portion (19.4%) of long branch chains (DP>37) than the other three starches (16.2-16.9%). The average amylopectin branch chain lengths ranged from 22.9-24.2. The maximum detectable DP was higher in Keoma (71) than in the other three starches (64-65). The X-ray pattern was of (C type. The relative crystallinity was in the range 20.8-25.1%. The proportion of 'B' polymorphic form was higher in Keoma (25.6%) than in the other three starches (22.1 to 24.1%). There were no significant differences in swelling factor. The extent of amylose leaching at 95°C ranged from 25.20-26.85. All four starches exhibited nearly identical gelatinization transition temperatures. However, the gelatinization temperature range (TC-TO) followed the order: Grande ~ Keoma > Carneval ~ Carrera. The four starches showed identical pasting temperatures and exhibited only marginal differences with respect to 95°C viscosity and to the increase in consistency during the holding period at 95°C. However, the set-back viscosity for Carneval was lower than that of the other starches. There were no significant differences in the extent of acid hydrolysis. However, susceptibility towards α-amylase followed the order: Carneva I~ Carrera ~ Grande > Keoma. The magnitude of changes in transition temperatures and enthalpy, and the broadening of the endotherm during retrogradation (24h) at different storage temperatures (4 and 40°C), followed the order: 4°C/24h > 4°C/24h + 40°C/24h > 40°C/24h. The extent of retrogradation (assessed by changes in enthalpy) followed the order: Carneval ~ Grande ~ Carrera > Keoma. There were no significant differences in the extent of freeze-thaw stability. The results showed that Keoma differed from the other three starches with respect to amylopectin branch chain length distribution, 'B' polymorphic composition, enzymatic digestibility, and degree of amylopectin retrogradation.

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