Relationship between proportion and composition of albumins, and in vitro protein digestibility of raw and cooked pea seeds (Pisum sativum L.).

BACKGROUND: Peas provide an excellent plant protein resource for human diets, but their proteins are less readily digestible than animal proteins. To identify the relationship between composition and in vitro digestibility of pea protein, eight pea varieties with a wide range of protein content (157.3-272.7 g kg(-1)) were determined for the proportion of albumins and globulins, their compositions using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and in vitro protein digestibility (IVPD) before and after heat treatment using a multi-enzyme (trypsin, chymotrypsin and peptidase) method.
RESULTS: The proportion of albumins based on total seed protein content decreased from 229 to 147 g kg(-1) as seed protein content increased from 157.3 to 272.7 g kg(-1), while the proportion of globulins increased from 483 to 590 g kg(-1). The IVPDs of eight raw pea seeds were 79.9-83.5%, with significant varietal variations, and those were improved to 85.9-86.8% by cooking. Albumins, including (pea albumins 2) PA2, trypsin inhibitor, lectin and lipoxygenase, were identified as proteolytic resistant proteins. Globulins were mostly digested by protease treatment after heating.
CONCLUSION: The quantitative ratio of albumins and globulins, and the quantitative variations of albumin protein components, including lipoxygenase, PA2, lectins and trypsin inhibitors, appear to influence the protein digestibility of both raw and cooked pea seeds. Copyright (c) 2010 Society of Chemical Industry.