Abstract:In order to further explore the protein changes of mutton during freezing-thawing process, differential scanning calorimetry (DSC) was used to study the changes of Xinjiang mutton under four freeze-thaw procedures, including non-freezing-thawing (NFT), one cycle of freezing-thawing at -20 ℃(TFT1), two cycles of freezing-thawing at -20 ℃ (TFT2) , and one cycle of freezing-thawing at -80 ℃(EFT1). The effects of the freezing-thawing cycles, minimum freezing-thawing temperature and duration of sample preparation and measurement on the DSC enthalpy curve were analyzed. The results showed that the temperature of protein denaturation shifted after freezing-thawing process. Compared with the NFT group, the peak enthalpy of myosin in TFT1 and EFT1 groups decreased by 57.0% and 89.6% (P<0.05), respectively, and the heat absorption peak enthalpy of actin in TFT1, TFT2 and EFT1 groups decreased by 47.0%, 68.8% and 59.6% (P<0.05), respectively. The heat absorption peak enthalpy of rapid moisture transpiration in TFT1 and TFT2 groups increased by 1.3% (P<0.05) and decreased by 11.9% (P<0.05), respectively, while that of EFT1 group increased by 15.6% (P<0.05). In PCA analysis, there was a significant negative correlation between the duration from sample preparation to measurement and the thermal absorption peak enthalpy of actin, while sample weight had no obvious effect on other indexes. The results showed that the increase of freezing-thawing cycles increased the denaturation degree of myosin and actin, showing a more significant effect on myosin. Under the same cooling rate, the decrease of minimum freezing-thawing temperature could aggravate the denaturation of protein, but the moisture loss during the cycle could be reduced. There was a positive correlation between the duration between sample preparation and measurement and the degree of actin degeneration.
