Abstract: This study was conducted to analyze the effects of thawing at different relative humidity (RH 80%, 85%, 90% and 95%) and viable low temperature (2 ℃ → 6 ℃ → 2 ℃) on the quality characteristics of pork by using fresh pork and conventional low temperature thawing (4 ℃, RH 65%–73%) as the controls. The changes in thawing rate, physicochemical characteristics including water-holding capacity (WHC), color, tenderness and freshness, protein thermal denaturation and rheological properties were examined. The results showed that compared with conventional low temperature thawing, variable low temperature, high humidity thawing could improve the thawing efficiency (P < 0.05), maintain the WHC, color and tenderness of pork, and inhibit lipid oxidation significantly (P < 0.05). The thawing efficiency at RH of 90% and 95% was higher than at RH of 85% and 80%. In addition, viable low temperature thawing at RH of 90% and 95% allowed better maintenance of WHC, color and tenderness (close to fresh pork), reduced lipid oxidation and increased protein solubility. The degree of protein denaturation in the thawed pork at RH of 90% and 95% was significantly lower than at RH of 80% and 85% (P < 0.05) as measured by differential scanning calorimetry (DSC). Also, the thawing at RH of 90% and 95% maintained the G′ value better. However, total bacterial count (3.97(lg(CFU/g))) and TVB-N content (1.40 mg/100 g) in the thawed pork at 95% RH were significantly higher than other thawed samples. Moreover, greater humidity could require higher energy consumption. Therefore, variable low temperature combined with 90% relative humidity thawing was more suitable for frozen pork .

Key words: viable low temperature thawing, relative humidity, pork, physicochemical characteristics, differential scanning calorimetry, rheological properties