The influence of thermal processing on the non-starch polysaccharide (NSP) content and in vitro digestibility of starch in peas (Pisum sativum, L.)

Abstract

The non-starch polysaccharide (NSP) content and the effect of thermal processing on the digestibility of starch in vitro have been studied in two varieties of peas (Citrina and Warindo), which were classified into four commercial sizes according to seed diameter (super-fine, 4.7-7.5 mm; very-fine, 7.6-8.2 mm; fine, 8.3-8.8 mm; middle, 8.9-10.2 mm). The samples used frozen raw peas, frozen cooked peas and canned peas. The NSP content was measured by the Englyst procedure with GLC, and the three main fractions of starch (rapidly digestible starch, RDS; slowly digestible starch, SDS; resistant starch, RS) were determined as glucose released after controlled enzymic hydrolysis in vitro. The results showed an increase of total starch and a decrease of total NSP during seed development. Total starch was around 300 g/kg whereas total NSP ranged from 135 to 291 g/kg. Thermal processing caused a redistribution of the insoluble and soluble components of NSP, with cooking increasing the solubility. The overall digestibility of starch was increased in processed peas, super-fine and very-fine pea sizes showing a higher starch digestibility rate index than frozen raw peas. This increase was reflected in an increase in the RDS fraction and a decrease in both SDS and RS. © 1996 Academic Press Limited.