Enzymatic hydrolysis of extruded soybean meal at high substrate concentrations

Extrusion as a pretreatment before enzymatic hydrolysis of soybean meal is an effective technique to eliminate antinutritional properties of the main thermostable soy proteins glycinin and ?-conglycinin for production of feed ingredients with enhanced properties. In terms of economic efficiency, biotechnological processes are preferable to carry out at high substrate concentrations. The aim of the investigation was to evaluate the influence of high substrate concentrations in the range of 26-32% and enzyme dosages (0.4 - 3.1 PU/g) on efficiency of hydrolysis of extruded toasted soybean meal with bacterial protease. The results showed that maximum degree of hydrolysis was 42.1% at the enzyme dosage of 3.6 PU/g and at the substrate concentration of 29.0%. The increase in the substrate concentration had a strong effect on the deterioration of dynamic viscosity of the hydrolysates from 0.2 to 5.82 Pa?s. A combination of extrusion cooking at 120?C and enzymatic treatment with ?Protolad B? protease enabled hydrolysis of glycinin and ?-conglycinin to peptides with molecular mass below 15 kDa.