温度、pH值和碱质量分数对牦牛奶曲拉干酪素提取得率和品质的影响

Effect of the temperature,pH value and alkali concentration on the of extraction yield and quality of casein from yak milk Qula

利用高效液相色谱法对牦牛乳干酪素的5-羟甲基糠醛质量浓度进行测定，评定溶解温度、pH值、碱质量分数对其美拉德反应的影响程度，并筛选出曲拉最佳溶解工艺参数，以提高产品感官品质和提取得率。结果表明，甘孜及周边地区曲拉理化成分较其他地区有所差别。在25～65℃的温度范围内，得率受温度影响差异显著，且感官评分与温度呈负相关，5-HMF质量浓度随着温度上升而增加；在7．5～11．5的pH值范围之内，随着pH值增加，牦牛曲拉干酪素提取得率和5-HMF质量浓度增加，感官评分降低；在8％-24％的碱质量分数范围内，随着碱质量分数的增加，提取得率及5-HMF质量浓度增加，感官评分下降不显著，综合各指标，最佳溶解工艺参数为温度35℃、pH值为10．5和碱质量分数为20％；验证显示，该组合得率达到78．67％±0．31％，感官评分为7．9±0．3，5-HMF检测质量浓度为0．728±O．082mg／L。该研究建立了一套较优的牦牛曲拉干酪素提取工艺，为曲拉干酪素有效提取及品质检测提供了新方法。

HPLC was used for the measurement of 5-hydroxymethyl furfural content of yak milk casein to evaluate the extension of Maillard reaction. Solution temperature, pH value, and concentration of alkali were considered for the Maillard reaction, extraction yield and sensory evaluation. To improve the sensory quality of products and the extraction rate, dissolution process parameters were screened and optimized. The results showed that the percentage of moisture, protein, fat, ash in Qula in the area of Ganzi and its surrounding area were different from others. In the range of 25-65℃ temperature, the extraction rate increased. At 55 ℃ reached the maximum rate, 90.60%. Extraction rate was significantly affected by temperature and sensory evaluation and temperature showed negative correlation, the content of 5-HMF with the temperature rise and increased; at a range of pH value 7.5±11.5, with the increase of pH value, yak milk casein ex- traction yield and 5-IqMF content increasedand sensory score was lower; in the range of 8%±24% alkali concentration, the extraction rate and 5-HMF content increased and sensory score declined, but was not significant. Based on comprehensive consideration, .optimal dissolu- tion process parameters for casein extraction were： temperature 35 ℃, pill0.5 and alkali concentration of 20%; after repeated three times to verify that the combination, the extracted rate reached 78.67±0.31%,sensory score was 7.9±0.3, and 5-HMF content was 0.728 ± 0.082 （mg/L）. The study has established a better yak milk casein extraction method, and provides a new technology for effective extrac- tion of Qula casein and quality detection.