EFFECT OF PROTEASE TREATMENT OF SOYBEAN-MEAL ON CONTENT OF TOTAL SOLUBLE MATTER AND CRUDE PROTEIN AND LEVEL OF SOYBEAN TRYPSIN-INHIBITORS

An in vitro study was undertaken to determine the effect of treating s oybean meal with protease at different temperature and pH conditions o n the content of total soluble matter and crude protein (CP) and the l evel of soybean trypsin inhibitors (SBTI). Soybean meal (5 g), weighed into 25 X 150 mm culture tubes, was suspended in 20 mi of distilled w ater, adjusted to pH 3, 4.5 or 6, with Bacillus subtilis subtilisin-pr otease (Finnfeeds International) at 0, 0.2 or 1.0 mg g(-1) soybean mea l. The culture tubes were incubated for 16 h in a temperature-controll ed water bath at 40 or 50 degrees C. The soluble and insoluble fractio ns of soybean meal were separated by centrifuging the culture tubes an d decanting the supernatant into separate conical tubes. All tubes wer e freeze-dried and the contents analyzed for CP. The content of total soluble matter and CP, on a dry matter basis, were determined as the d ifference between the beginning and end weight of the culture tubes. T he content of total soluble matter and CP and the level of SBTI were u sually similar (P > 0.05) for soybean meal treated with protease at 0 or 0.2 mg g(-1). Protease pretreatment at 1.0 mg g(-1) soybean meal in creased (P < 0.05) the content of soluble CP and, with the exception o f incubation at 50 degrees C and pH 6, lowered (P < 0.05) the level of SBTI compared with soybean meal pre-treated with protease at 0 or 0.2 mg g(-1) under all conditions of temperature and pH. Based on the res ults of this in vitro trial, protease pretreatment at 1.0 mg g(-1) soy bean meal has the potential to improve the availability and digestion of soybean meal protein in diets for pigs. (C) 1998 Elsevier Science B .V.