Germination as a processing technique for soybeans in small-scale farming

Abstract

Heat processing is an effective way of reducing antinutritional factors (ANFs) in legumes, but requires expensive facilities and equipment. Accurate control of temperature is critical to avoid under- or overheating. Therefore, heat treatment of soybeans is not a viable option for the average small-scale farmer in remote areas. Germination and other traditional methods, namely soaking and dehulling, were evaluated as alternative processing methods for soybeans. The effect of the processing treatment on the level of different ANFs, nutritional composition and in vitro protein digestibility (IVPD) of soybean seeds was determined. Soybeans were soaked for 24 hours and allowed to germinate for one to six days. Soaked soybeans were manually dehulled. Changes within seeds were noted for nutritional and ANFs during germination. Crude protein and fat content increased with increasing number of days germinated, but germination caused a decrease in starch content. Dehulling also increased the crude protein and fat content of the seeds. All treatments caused a significant decrease in condensed tannins of the soybeans. Trypsin inhibitor levels were numerically lower after germinating, soaking and dehulling of seeds, but not significantly so. There were no changes in IVPD after treatment of the soybeans. It was concluded that germination for a period of three days effectively improved the nutritional value of soybeans and can be considered an alternative treatment of soybeans for the small-scale farmer where heat treatment is impractical or impossible.

Keywords: Soybeans seed, Glycine max, TIA, anti-nutritional factors, traditional methods