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首页> 外文期刊>Australian Journal of Dairy Technology >Cross-linking of proteins and other changes in UHT milk during storage at different temperatures
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Cross-linking of proteins and other changes in UHT milk during storage at different temperatures

机译：在不同温度下储存期间，蛋白质的交联和UHT牛奶中的其他变化

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摘要

Many chemical changes take place in UHT milk during storage. In this work UHT milk was stored at different temperatures (5 degrees C, 20 degrees C, 37 degrees C and 45 degrees C) for 12 weeks and assessed for pH, browning, proteolysis and protein changes by HPLC, PAGE and lysinoalanine determination. There was a greater decrease in pH and increase in browning, due to Maillard reactions, and proteolysis in samples stored at 37 C and 45 degrees C than in samples stored at 5 degrees C and 20 degrees C; these changes were positively related to both time and temperature of storage. The RP-HPLC chromatogram of the proteins in the UHT milk samples stored at 45 degrees C changed considerably during storage and at the end of 12 weeks' storage was completely different from that of a sample stored at 5 degrees C, indicating that considerable change takes place in the proteins of samples stored at elevated temperature. Lysinoalanine concentration, an indicator of covalent, non-disulfide cross-linking of proteins, increased with storage temperature and time. The cross-linking was also observed by reduced SDS-PAGE from which the percentages of cross-linked milk proteins were estimated to be 1.1%, 1.3%, 7.0% and 36.8% after 12 weeks' storage at 5 degrees C, 20 degrees C, 37 degrees C and 45 degrees C, respectively.
机译：在储存过程中，UHT牛奶发生了许多化学变化。在这项工作中，UHT牛奶在不同温度（5摄氏度，20摄氏度，37摄氏度和45摄氏度）下存储12周，并通过HPLC，PAGE和赖氨酸丙氨酸测定来评估pH，褐变，蛋白水解和蛋白质变化。在37°C和45°C下储存的样品中，由于美拉德反应和蛋白水解作用，与在5°C和20°C下储存的样品相比，pH降低和褐变增加更大;这些变化与储存时间和温度均呈正相关。在45摄氏度下储存的UHT牛奶样品中蛋白质的RP-HPLC色谱图在储存过程中发生了很大变化，在12周储存结束时与在5摄氏度下储存的样品完全不同，这表明需要进行相当大的改变放置在高温下保存的样品蛋白质中。赖氨酸丙氨酸浓度是蛋白质共价，非二硫键交联的指标，随储存温度和时间的增加而增加。还通过减少的SDS-PAGE观察到了交联，在5℃，20℃下储存12周后，据估计交联的乳蛋白的百分比分别为1.1％，1.3％，7.0％和36.8％。分别为37摄氏度和45摄氏度。

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