超高压对牛乳纤溶酶和脂肪酶的钝化效应研究

THE EFFECT OF ULTRA HIGH PRESSURE TREATMENT OF BOVINE MILK ON PLASMIN AND LIPASE ACTIVITIES

以牛乳中纤溶酶和脂肪酶为研究对象,在40MPa～900MPa压力下结合几种施压介质温度、施压时间和施压方式处理鲜乳,分析了各因素对牛乳中纤溶酶和脂肪酶活性的影响。研究结果表明,在40MPa～80MPa处理条件下,乳中纤溶酶和脂肪酶的活性都有所提高,但压力对提高酶活性的作用不显著(P>0.05)。在室温、500MPa～900MPa施压条件下,900MPa处理4min能使纤溶酶和脂肪酶完全钝化。在室温、350MPa～850MPa施压条件下,纤溶酶和脂肪酶的最小钝化压力均在450MPa～500MPa,850MPa和750MPa施压条件可使纤溶酶和脂肪酶完全钝化。压力对两种酶的钝化效应极显著(P<0.01),而施压时间和施压方式对酶的钝化效应不显著(P>0.05)。在不同的施压方式下,间歇式施压对酶的钝化效应明显。钝化纤溶酶的最佳工艺参数为850MPa、间歇式加压处理4min,钝化脂肪酶的最佳工艺参数为750MPa、间歇式加压处理8min。

Various ultra high pressure （40 MPa to 900 MPa） treatments were applied at different temperatures for different time intervals to investigate bovine milk plasmin and lipase activities. When ultra high pressure was applied between 40 MPa and 80 MPa, plasmin and lipase activities increased. But the results were not significant （p 〉 0.05）. When pressurized at an ambient temperature between 500 MPa and 900 MPa, the activities of both plasmin and lipase were completely inactivated at 900 MPa after four minutes of treatment. When pressurized at an ambient temperature between 350 MPa and 850 MPa, the minimum pressure needed to inactivate plasmin and lipase was between 450 MPa and 500 MPa. When pressure was increased to 750 MPa, lipase was completely inactivated. When pressure was increased up to 850 MPa, plasmin was completely inactivated. Pressure treatment had a significant effect （p 〈 0.01） on inactivating these enzymes （plasmin and lipase）. However, time intervals and means of ultra high pressure treatments had no significant effect （p 〉 0.05） on the inactivation of plasmin and lipase. Among the means of ultra high pressure treatments, pulsed treatment was more effective than the others on inactivation of enzymes. The optimum pressure with pulsed treatment to inactivate plasmin was applied at 850 MPa and held for as long as four minutes. The optimum pressure with pulsed treatment to inactivate Lipase was applied at 750 MPa and held for as long as eight minutes.