Functionality of myofibrillar proteins as affected by pH, ionic strength and heat treatment - a low-field NMR study

Myofibrills were extracted from porcine muscle, and their water properties were characterized using low-field nuclear magnetic resonance (NMR) T-2 relaxometry. A T-2 relaxation pattern very similar to the pattern observed in intact meat and water contents comparable to the water content in meat were observed, implying that the myofibrillar structures are responsible for retaining the majority of water in meat. The effect of pH and ionic strength in the samples was investigated as pH was adjusted to 5.4, 6.2, and 7.0 and ionic strength to 0.29, 0.46 and 0.71 M, respectively. Even though there were interactions between pH and ionic strength, the water content in the samples increased significantly with increasing pH and ionic strength. Moreover, mean T-2 relaxation times likewise increased with increasing pH and ionic strength, which reveals that the increased water retention could be ascribed to a swelling of the myofibrils and thereby increased spacing between filaments. The present study demonstrates that NMR T2 relaxometry is a potential tool to explore how processing factors such as pH and ionic strength affect the microstructure of meat. (C) 2004 Elsevier Ltd. All rights reserved.