KINETICS OF AVAILABLE LYSINE LOSSES IN A SOY PROTEIN ISOLATE: CONFIRMATION OF THE ‘TRANSITION PHASE’ BY PROTEIN EFFICIENCY RATIO TESTS

摘要

ABSTRACTAvailable lysine losses in soy protein isolates during thermal processing go through three phases: a fist‐order loss, a transition phase and a no‐loss phase. The transition phase shows a statistically significant (P<0.02) increase in available lysine when measured by the fluoro‐dinitrobenzene (FDNB) method. Using the protein efficiency ratio method (PER), a statistically significant (P<0.1) increase in available lysine was demonstrated in samples processed at 80° C for 700 mm. The PER values decreased from 2.65 ± 0.04 to 1.17 ± 0.04 after 600 min of processing. At 700 min the PER value increased to 1.37 ± 0.05. At 80°C the transition phase in systems containing 4 sugar occurs 600 mm after processing is initiated according to previously published equations. The PER and FDNB results exhibited an excellent correlation (r = 0.98). Thus, PER results confirm the increase detected using the FDNB