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(30 kV/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℃,21 s)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30 kV/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 30kV/cm for 500μs,color and viscosity of carrot juice were stable.However,total phenolic content and total carotenoid content increased by different extents.Nevertheless,HTST(98℃,21s) 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 30kV/cm and extending treatment time to 800μs,residual activity 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.