高压脉冲电场对鲜榨胡萝卜汁的品质和内源酶活力影响

对比研究了高压脉冲电场（PEF）处理和高温短时巴氏杀菌（HTST）对鲜榨胡萝卜汁品质和内源酶活力的影响．两种杀菌处理方式对胡萝卜汁的pH值、总酸度、可溶性固形物含量、还原糖含量影响不显著．在PEF（30kV／cm，500μs）条件处理下，胡萝卜汁色泽、黏度均未发生显著变化，而总酚和类胡萝卜素总量均有所提高．在HTST（98℃，21s）条件处理下，胡萝卜汁会发生褐变，黏度显著变大，总酚含量显著下降．结果表明PEF处理后的胡萝卜汁理化性质、营养成分比高温短时巴氏杀菌更接近新鲜胡萝卜汁．随着脉冲场强增加至30kV／cm和PEF处理时间延长至800μs，胡萝卜汁中的脂肪氧化酶（LOX）和过氧化物酶（POD）相对酶活（RA）最低分别降至23．22％和46．97％，LOX对PEF参数变化更为敏感．经HTST处理后，LOX和POD相对酶活分别降至19．21％和48．08％．

Effects of Pulsed Electric Fields on Quality and Endogenous Enzymes Activity of Freshly-squeezed Carrot Juice

The effects of pulsed electric fields （PEF） and high temperature short time pasteurization （HTST） on quality characteristics and endogenous enzyme activity of freshly-squeezed carrot juice were investigated. There is no significant change in pH, total acidity, °Brix, reducing sugar content after PEF and HTST. With PEF treatment at 30 kV/cm for 500 μs, color and viscosity of carrot juice were stable. However, total phenolic content and total carotenoid content increased by different extents. Nevertheless, HTST （98℃ , 21 s） caused color deterioration and significant increase in juice viscosity （P 〈 0.05） but a significant decrease in total phenolic content （P 〈 0.05）. Compared with HTST-Pasteurized carrot juice, the quality properties of PEF-treated carrot juice were closed to those of untreated carrot juice. With pulsed electric intensity increased to 30 kV/cm and extending treatment time to 800μs, residual ac-tivity of lipoxidase （LOX） and peroxidase （POD） decreased to 23.22% and 46.97%, respectively. LOX was susceptible to PEF treatment. With HTST treatment, residual activity （RA） of LOX and POD decreased to 19.21% and 48.08% , respectively.