Heat-induced changes in myofibrillar protein structures and myowater of two pork qualities.: A combined FT-IR spectroscopy and low-field NMR relaxometry study

Low-field NMR T-2 and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 degrees C to 81 degrees C. Pronounced changes in both T-2 relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700-1600 cm(-1)), and a tentative assignment of these is discussed. Distributed NMR T-2 relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting beta-sheet and alpha-helix structures and the NMR relaxation populations reflecting hydration water (T-2B similar to 0-10 ms), myofibrillar water (T-21 similar to 35-50 ms), and also expelled "bulk" water (T-2 relaxation times > 1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical-physical properties of the water within the meat.