Enzymatic extractability of soybean meal proteins and carbohydrates: Heat and humidity effects

To study the incomplete enzymatic extractability of proteins and carbohydra tes of thermally treated soybean meals, one unheated and three heat-treated soybean meals were produced. To obtain truly enzyme-resistant material, th e meals were extracted by a repeated hydrolysis procedure using excessive c oncentrations of different combinations of commercial protease and carbohyd rase preparations. The water extractability of protein from the different m eals varied considerably (13-67%). For all soybean meals, enzymatic treatme nt extracted most of the original protein (89-94%). Carbohydrase preparatio ns did not improve protein extraction. High-humidity heat treatment led to a more effective enzymatic extraction, which seemed to correlate with the e xtent of protein denaturation. Results with purified proteins indicated tha t the soybean meal matrix affects the enzymatic extraction of protein from the meals. Interactions between protein and other components (e.g., cellulo se) may explain the incomplete enzymatic extractability of protein from the meals.