Effects of Steam Conditioning and Extrusion Temperature on Some Anti-nutritional Factors of Soyabean (Glycine max) for Pet Food Applications

Extrusion processing of vegetable ingredients such as soyabean (Glycine max) characteristically depends on associating process conditions that influence the product qualities. The process parameters were optimized for extrusion of steam-conditioned material in order to obtain the maximum nutritive value by inactivating the anti-nutritional factors such as urease, trypsin inhibitors and lipase. The processing conditions such as moisture content, temperature and time were precisely controlled to avoid over heating or under heating which otherwise would result in a product of lower nutritional quality. The urease activity and Trypsin inhibitors were measured in steam conditioned extruded soyabean material and test results indicated that urease activity units and trypsin inhibitory units were reduced from 2.0 and 50 to 0.3 and 5 respectively in extruded soyabean during the extrusion process. These results were used for comparative evaluation of 'inactivation levels of anti-nutritional factors' for optimizing the processing conditions of the steam conditioner and extruder for producing soyabean products for pet food applications. Stability studies were done on pet food samples and free fatty acid content and peroxide values were used as the criteria to evaluate the lipase activity in extruded soyabean samples. Extrusion of steam-conditioned soyabean material inactivated the antinutritional factors making extruded soyabean an ideal ingredient for pet food and its stability.