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W. S. RATNAYAKE¹, R. Hoover¹, F. Shahidi¹, C. Perera², and J. L. Jane². (1) Department of Biochemistry, Memorial University of Newfoundland, St. John's, NF A1B 3X9, (2) Department of Food Science and Human Nutrition, Iowa State University, IA 50011

Processes for the air-classification of finely ground field peas have permitted the fractionation of the flour into protein and starch concentrates (60 - 80% of starch). However, due to its poor functional properties, the starch concentrate is not used in food formulations. Starches from different cultivars of cereals and tubers have been shown to vary in structure, composition and properties. However, such variations among field pea cultivars have not been the subject of a detailed study. Most of the studies on field pea starch have been on a single cultivar. Therefore, it is difficult to ascertain whether the data reported truly represent the properties of field pea starch.

The objective was to investigate and relate the molecular structure of four different field pea cultivars to their functional properties.

Differential scanning calorimetry, X-ray diffraction, gel permeation chromatography, high pressure anion exchange chromatography and Brabender amylography and AACC approved methods were used in this study.

The total amylose content was in the range of 48.81-49.57% and the amount of native lipids complexed with amylose ranged from 10.88% (Carneval) to 12.26% (Carrera). There were no significant (p < 0.05) differences in swelling factor, extent of acid hydrolysis and retrogradation rates among the starches. The extent of hydrolysis by a-amylase followed the order: Carneval > Carrera > Grande > Keoma. All four starches exhibited nearly identical gelatinization transition temperatures. However, DH followed the order: Carneval > Keoma > Carrera > Grande. The X-ray diffraction patterns were of 'C' type. The relative crystallinity was in the range of 20.83% (Carrera) to 25.06% (Carneval). The proportions of the 'B' polymorphic form ranged from 22.11% (Carrera) to 25.56% (Keoma). The average degree of polymerization of amylose was in the range of 1300-1350. The average amylopectin chain length was in the range 22-24.

This study will help us to tailor field pea starch for specific applications.