The effect of extrusion cooking on mineral bioavailability in pea and kidney bean seed meals

Abstract

The effects of extrusion cooking on chemical composition, contents of minerals, carbohydrates and antinutritional factors (inositol phosphates, condensed tannins and lectins) in pea ( Pisum sativum L.) and kidney bean ( Phaseolus vulgaris L.) seed meals were investigated. In addition, mineral bioavailability in growing rats of diets based on extruded or raw pea or kidney bean meals, as the only protein source was determined. Moisture content decreased and iron increased in extruded compared with non-treated seed meals. Starch and NSP were reduced ( P<0.05) in both pea and kidney bean seed meals. Raffinose, stachyose and verbascose also dropped in kidney bean meal after extrusion, but only stachyose was reduced by thermal treatment in pea flours. Inositol hexaphosphate was partially hydrolysed to penta- and tetraphosphates by extrusion, which also lowered tannin and lectin content ( P<0.05). The apparent absorption of Fe, Ca and P from unsupplemented pea-based diets significantly increased in extruded compared with raw seed meals. With amino acid supplemented pea diets, extrusion significantly ( P<0.05) increased Ca, Mg, Fe, Cu and P apparent (faecal) absorption in rats. Extrusion increased ( P<0.05) Ca, Mg, Zn, Cu and P apparent (faecal) absorption in rats fed with both unsupplemented and supplemented kidney bean-based diets.