In vitro accessibility of untreated, toasted, and extruded soybean meals for proteases and carbohydrases

The in vitro accessibility of the water unextractable solids (WUS) from untreated, toasted, and extruded soybean meals toward different enzyme activities was studied. WUS was incubated with seven commercial enzyme preparations. Two enzyme preparations were selected for further research. Upon addition of Neutrase, the extruded sample yielded considerably more solubilized protein compared with the toasted and untreated soybean meals. Energex solubilized high amounts of neutral sugars after heat treatments compared with the untreated meal. Cell wall polysaccharides solubilized by the enzymes were released as small oligosaccharides and monosaccharides. SDS-PAGE analysis showed that after enzyme addition to the extruded sample, proteins were more rapidly and completely degraded compared with enzyme addition to the toasted and untreated soybean meals. Neutrase degraded both beta-conglycinin and glycinin. Energex could only, partly, degrade beta-conglycinin. The basic polypeptide from glycinin showed the highest resistance against proteolytic activity.