Trypsin Inhibitor Activity in Laboratory- Produced and Commercial Soymilk

摘要

Trypsin inhibitor activity (TIA) in soymilk processed by traditional, steam injection, blanching and UHT methods were determined and compared to commercial soymilk products. Soybeans were soaked and blanched under several selected conditions. The blanched beans were made into base soymilk. Hexanal of the base soymilk was analyzed as a soy odor marker for selecting the best conditions for further thermal processing by indirect and direct UHT methods at 135-150 C for 10-60 s using the Microthermics DIP processor. Soymilk was also made by traditional batch stove cooking and steam injection methods. TI activities of eighteen commercial products were tested for comparison. Results showed residual TIA in soymilk processed by the traditional and steam injection to 100 C for 20 min were approximately 13%. Blanching inactivated 25-50% of TI activities of the raw soymilk. The blanching conditions of 80 C and 2 min were selected for UHT processing since these conditions produced blanched soymilk without hexanal. The TI activity decreased with increased temperature and time of heating. The maximal TI inactivation was achieved by UHT direct and indirect methods with residual activities of approximately 10%. Heat inactivation (denaturation) of TIA followed first-order reaction kinetics. Some commercial soymilk products contained high TIA. TI has recently been found to have health benefits. The importance of trypsin inhibitors to the food industry and consumers was discussed.