LIPOXYGENASES AND TRYPSIN-INHIBITORS INACTIVATION IN A SOYMILK PROCESSING BY DIRECT MILLING AND ULTRA-HIGH TEMPERATURE (DM-UHT)

Soymilk production by a new process based on Direct Milling of soy gri ts and Ultra High Temperature (DM-UHT) has been studied at laboratory scale in order to evaluate solids and protein extraction, lipoxygenase s (LO) and Trypsin Inhibitors CTI) inactivation during milling and hea t-treatment steps. For TI measurements in soy extracts and soymilk a m odification of the classical Kakade method (17) was used. Highest extr action yields were accomplished at 70 degrees C and 2 minutes milling of soy grits. LO was appreciably inactivated when using, as dispersing medium for milling, 0.01M sodium carbonate (Residual Activity 14%) in stead of water (Residual Activity 46%), so in this way lower levels of undesired substances can be generated. LO destruction in the resultin g suspension was finished by a short heating (30 seconds) from 70 degr ees C to boiling temperature (96 degrees C). On the other hand, TI wer e not fully inactivated in milling nor even in the steaming step at 96 degrees C for many minutes. The TI were inactivated to the accepted l evels for soymilk in the final UHT step at 135 degrees C and 2 minutes , being possible at the same time to carry out the simultaneous microo rganisms destruction.