Riahi Esmaeil, Ramaswamy Hosahalli S
Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, Ste. Anne de Bellevue, PQ, Canada H9X 3V9.
Biotechnol Prog. 2003 May-Jun;19(3):908-14. doi: 10.1021/bp025667z.
High-pressure (HP) inactivation kinetics of pectin methyl esterase (PME) in apple juice were evaluated. Commercial PME was dispensed in clarified apple juice, sealed in dual peel sterilizable plastic bags, and subjected to different high-pressure processing conditions (200-400 MPa, 0-180 min). Residual enzyme activity was determined by a titration method estimating the rate of free carboxyl group released by the enzyme acting on pectin substrate at pH 7.5 (30 degrees C). The effects of pressure level and pressure holding time on enzyme inactivation were significant (p < 0.05). PME from the microbial source was found to be more resistant (p < 0.05) to pressure inactivation than PME from the orange peel. Almost a full decimal reduction in the activity of commercial PME was achieved by HP treatment at 400 MPa for 25 min. Inactivation kinetics were evaluated on the basis of a dual effect model involving a pressure pulse effect and a first-order rate model, and the pressure sensitivity of rate constants was modeled by using the z-value concept.
评估了苹果汁中果胶甲酯酶（PME）的高压（HP）失活动力学。将市售PME加入澄清苹果汁中，密封于可双封皮杀菌的塑料袋中，并置于不同的高压处理条件下（200 - 400 MPa，0 - 180分钟）。通过滴定法测定残余酶活性，该方法通过估算在pH 7.5（30℃）下酶作用于果胶底物释放游离羧基的速率来进行。压力水平和保压时间对酶失活的影响显著（p < 0.05）。发现微生物来源的PME比橙皮来源的PME对压力失活更具抗性（p < 0.05）。通过在400 MPa下高压处理25分钟，几乎使市售PME的活性完全下降一个对数单位。基于涉及压力脉冲效应和一级速率模型的双重效应模型评估失活动力学，并使用z值概念对速率常数的压力敏感性进行建模。
