76D-4 |
Interaction of myofibrillar and enzyme hydrolyzed soy proteins |
J. FENG and Y. L. Xiong. Department of Animal Sciences, Food Science Section, University of Kentucky, 211 W.P. Garrigus Building, Lexington, KY 40506 Soy protein is a common ingredient in processed meats. However, high denaturation temperatures of the main components (7S and 11S) render soy protein not ready to interact with meat proteins under meat processing conditions. To enhance protein-protein interaction, and thus, improve the functionality of soy protein, it is important to make soy protein structurally compatible with meat proteins. Our objective was to examine whether and how enzyme hydrolysis would modify soy protein structure and promote its interaction with myofibrillar proteins. Native and heated (85°C for 5 min) soy protein isolates (SPI) were hydrolyzed (4% DH) by Alcalase and Flavourzyme to obtain partially modified SPIs (AN, AH, FN, and FH). Samples were analyzed by size exclusion chromatography. Mixtures of hydrolyzed SPIs and pork muscle protein isolate (MPI) at various ratios were subjected to dynamic rheological testing (20 to 75°C at 1°C/min) for gelation, differential scanning calorimetry (20 to 120°C at 10°C/min) for protein thermal stability, electrophoresis for proteolytic changes, and back-extrusion for gel strength. Preheating accelerated SPI hydrolysis. Both enzymes effectively hydrolyzed 7S while 11S was less affected by Flavourzyme. 11S globulins in the hydrolysates showed higher denaturation temperatures. FN, FH and AH exhibited increased hydrophobicity. Native SPI and hydrolyzed SPIs did not gel upon heating up to 75°C. The denaturation temperatures of 11S decreased upon the addition of MPI, and the presence of hydrolyzed SPIs accelerated the disappearance of myosin heavy chain in the gelling process. Elasticity and hardness of the MPI-AH and MPI-AN gels were higher than those of the MPI-native SPI gel, which, in turn were higher than those of MPI-FN and MPI-FH gels. Our results suggested that limited hydrolysis by Alcalase improved the functionality of SPI in processed meats. The improvement may be attributed to the modification of 11S globulins.
Session 76D, Muscle Foods II
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