The effect of germination on the levels of certain antinutritional factors, nutritional composition and in vitro protein digestibility (IVPD) of soybean seeds were determined. Raw soybeans contain antinutritional factors, such as trypsin inhibitors (83.05 mg/g), total polyphenols (10.83%) and condensed tannins (1.24%). These factors limit the use of soybeans as a source of protein, carbohydrates and minerals in the poultry industry. In general, soybeans are subjected to heat treatment to reduce the amount of antinutritional factors within the seeds, but it is costly and needs high technology equipment. In order to assist small-scale chicken farmers or people living in developing countries, traditional or domestic processing methods are implemented to address the problem of antinutritional factors (ANFs) in soybeans. This study focused on germination as a versatile and low cost practice. Different lengths of germination time were assessed and compared to each another. Soybeans were soaked for 24 hours and allowed to germinate from one day up to six days. Changes within seeds were noted for nutritional and antinutritional factors during germination. Condensed tannins and trypsin inhibitors decreased significantly (P<0.05) while total polyphenols increased from 5 to 6 days. Protein and fat content increased significantly (P<0.05), but starch content decreased with germination. There were no significant changes for IVPD during germination of soybeans. Germination was also compared to other traditional methods such as roasting, soaking and dehulling. Results showed that dehulled soybeans had the highest proximate composition which was significantly different from other treatments (P<0.05), but the total polyphenols increased. It was concluded that germination for a period of three days effectively improved the nutritional value of soybeans and can be considered as an alternative treatment of soybeans in situations where heat treatment is impossible or impractical. Copyright
Dissertation (MSc(Agric))--University of Pretoria, 2011.