Abstract: The purpose of this study was to investigate the effects of different thawing methods on the quality of frozen pork by low field-nuclear magnetic resonance (LF-NMR) T2 transverse relaxation measurements. Chilled meat (semitendinosus muscle, at postmortem 27 h) was used as the control to measure the quality characteristics of refrigerated thawed meat, microwave-thawed meat samples 1 and 2 including thawing loss, cooking loss, water holding capacity (WHC), pH, color, water-soluble and salt-soluble protein content, water content correlated with T2 relaxation and sensory attributes. The results showed that the second microwave thawing process took the shortest time of 5 min. Compared with refrigerated thawing, microwave thawing exhibited lower thawing loss (P < 0.01), with the lowest value (5.31%) being observed for microwavethawed sample 2. Compared with fresh meat, microwave-thawed sample 2 had higher WHC (30.99%) and lower shear force value (19.49 N). All three thawing methods had no significant effect on meat pH (P > 0.05). The effect of microwave thawing on L*, a* and b* values and water-soluble and salt-soluble protein contents was better than that of refrigerated thawing, and the values of these parameters in microwave-thawed meat were closer to those in chilled meat. The moisture distribution as observed by NMR T2 relaxation imaging method showed that refrigerated thawing resulted in the transformation of immobilized water to free water, while microwave thawing 1 caused the opposite effect and microwave thawing 2 tended to transform immobilized water to bound water, which may explain the differences in the above quality characteristics. The sensory evaluation score of microwave-thawed meat samples was closer to that of fresh meat. Thus, microwave-thawing can better preserve the eating quality of pork.

Key words: pork, refrigeration, microwave, thawing, eating quality