羊肉冻融过程中蛋白质变性的DSC热学分析

DSC Thermal Analysis of Protein Denaturation in Mutton During Freezing-Thawing Process

为探究羊肉在冻融过程中蛋白质的变化,利用差示扫描量热(DSC)法研究新疆羊肉在未冻融(NFT)、-20℃冻融1次(TFT1)、-20℃冻融2次(TFT2)、-80℃冻融1次(EFT1)共4种冻融程序下的变化,并分析了冻融次数、最低冻融温度和制样到测样之间时长对DSC热焓曲线的影响。结果表明,冻融后蛋白质变性温度发生偏移;相较于NFT组,TFT1组和EFT1组的肌球蛋白热吸收峰焓值分别降低了57.0%和89.6%(P<0.05),TFT1组、TFT2组和EFT1组的肌动蛋白热吸收峰焓值分别降低了47.0%、68.8%和59.6%(P<0.05),TFT1组和TFT2组的水分迅速蒸腾热吸收峰焓值分别升高了1.3%(P>0.05)和降低了11.9%(P<0.05),EFT1组的水分迅速蒸腾热吸收峰焓值升高了15.6%(P<0.05);在PCA分析中,制样到测样之间时长和肌动蛋白热吸收峰焓值有明显的负相关关系,样品质量对其他指标影响不明显。因此,冻融次数增多使肌球蛋白和肌动蛋白变性程度均增加,且对肌球蛋白的影响更大;相同降温速率条件下,DSC冻融程序的最低温度降低,蛋白质变性加剧,但冻融过程中样品水分散失降低;制样到测样之间时长与肌动蛋白变性程度呈正相关关系。

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.