Chemical and nutritional properties of dry peas with emphasis on dietary fibre and saponins

The chemical composition and changes during development of dehulled light- and dark-hulled peas (Pisum sativum L.) were investigated. The dehulled light and dark peas had similiar chemical composition and were composed mainly of starch and crude protein. Dark-hulled peas had a higher hull content than light-hulled peas. Glucose and uronic acid residues were the two dominating dietary fibre polysaccharide residues in the hulls. The concentration of sucrose and glucose+fructose was high in the young dehulled seeds but descreased rapidly until the starch concentration reached its maximum early during development. The concentration of crude protein showed an opposite pattern to starch. The concentration of dietary fibre and raffinose series of oliogosaccharides generally increased during growth and maturation. Dietary fibre concentration in hulls increased dramatically during development. The content of soyasaponin I in dehulled peas varied considerably between samples, with a notable decrease during development. The effect of storage and extraction on ratio of soyasaponin I to chromosaponin I was studied. Both soyasaponin I chromosaponin I were present in the extracts of dehulled dried peas. The proportion of soyasaponin I to chromosaponin I increased with increasing extraction time as well as after storage of dry dehulled peas. The effects of diets based on dehulled peas was elucidated in a broiler chicken study. The diets consisted of 700 g kg-1 of milled or crushed dehulled peas with or without pectinase or alfa-galactosidase supplementation. Apparent ileal digestibility of organic matter, starch and crude protein was significantly lower for the crushed than the milled diets. Enzyme supplementation had no effect on apparent ileal digestibility. Apparent ileal and faecal digestibilities of nutrients were also determined in pigs fed a basal diet or diets substituted by 33% light- or dark-hulled peas. No differences were obtained in apparent ileal digestibility of nutrients between the two pea diets. However, the faecal apparent digestibilities of fibre components were generally lower in the dark-hulled pea diet than in either the basal or light-hulled diets.