Soymilk contains many functional components, but also Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI) which have trypsin inhibitor activities (TIA). TIA assay, ultracentrifugation, particle size distribution and Tricine-SDS-PAGE were used to examine TIA inactivation in soymilk. TIA assay showed residual TIA decreased with elevated temperature. Ultracentrifugation showed low residual TIA soymilk had more precipitate than the high one,and the residual TIA had high correlation coefficient (R2>0.9) with precipitate amount. It was found  >80% residual TIA was concentrated in the supernatant, and KTI and BBI in supernatant still existed as their protein molecules, while KTI and BBI in precipitate (large protein aggregate) had two states, incorporated into protein aggregate by disulfide or by noncovalent bonds. Thus, it was suggested the residual TIA was mostly resulted from the free KTI and BBI in supernatant and the TIA deactivation was resulted from the KTI and BBI incorporation into protein aggregate.

Heat-induced protein aggregate correlated with trypsin inhibitor inactivation in soymilk processing

244th National Meeting (2012)

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