Effect of extrusion, espansion and toasting on the nutritional value of peas, faba beans and lupins

Abstract

An assessment was made of the effect that different treatments (toasting, expansion, extrusion) have on the nutritional value of protein plants (pea, faba bean, lupin). In a randomized block design, feeds were screened for enzymatic digestibility of starch and protein, N solubility and in vitro protein degradability. Expansion and extrusion cause increased starch enzymatic degradability while toasting produced virtually no effects. In peas this value increased from 11.80% in meal to 39.70% in the extruded product; 85.37% is the percentage for the expanded product, while 10.90% is the starch digestibility value for toasted peas. In faba beans the extrusion process increased starch digestibility from 11.39% to 85.05%, while in extruded lupins a complete starch hydrolysis was obtained, while in the meal the polysaccharide digestion was 54.48%. The expansion and extrusion processes significantly decreased rumen degradability during the first 8 hours of incubation. Toasted peas had lower degradability if compared with controls but not with the other treatments. The only potentially alternative source to soybean is the extruded faba bean. In spite of its lower protein content, this feed is characterized by a considerably lower in vitro protein degradability than soybean. This implies that the digestible food protein content is comparable (124.90 g/kg DM) to that of soybean (109.78 g/kg DM) and definitely higher than that of all other protein plants.