Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, West Bengal 721302, India.
Agricultural and Food Engineering Department, Indian Institute of Technology Kharagpur, West Bengal 721302, India.
Food Res Int. 2017 Oct;100(Pt 1):885-893. doi: 10.1016/j.foodres.2017.07.056. Epub 2017 Jul 29.
The aim of the present work was to model the effect of combined pressure-temperature processing on spoilage-causing enzymes in mango pulp; which conventionally are inactivated using high temperatures leading to inevitable quality losses. The inactivation of enzymes pectin methylesterase (PME), polyphenol oxidase (PPO) and peroxidase (POD) was studied in mango pulp within the pressure, temperature and hold-time ranges of 0.1 to 600MPa, 40 to 70°C and 1s to 90min, respectively. The enzyme inactivation was described as a dual process: initial change in activity during dynamic pressure build-up phase and subsequent decrease under isobaric-isothermal conditions. The former led to considerable increase in activities of all the three enzymes (p<0.05); however, the increased activity reduced with increased intensity of applied pressure-temperature. On the other hand, isobaric-isothermal conditions led to substantial inactivation (p<0.05), with 600MPa/70°C/20min treatment being most effective in reducing the activities of PME, PPO and POD to 32, 15 and 26%, respectively. The enzyme inactivation data was non-linear under isobaric-isothermal conditions and fitted to the nth-order reaction model, indicative of the occurrence of series of reactions possibly due to pressure-temperature interaction effects. The estimated reaction order 'n' was 0.815, 1.106 and 1.137 for PME, PPO and POD, respectively. The estimated reaction rate constant k (min) depicted PME to be the most baroresistant enzyme followed by POD and PPO. Temperature and pressure dependency of k was expressed in terms of activation energy and activation volume using the Arrhenius- and Eyring-type relations, respectively. An empirical model with good correlation between actual and predicted data (R>0.90) was proposed to simulate the rate of enzyme inactivation under isobaric-isothermal conditions as a function of pressure and temperature.
本工作旨在对联合压力-温度处理对芒果浆中导致腐败的酶的影响进行建模；这些酶通常通过高温失活，导致不可避免的质量损失。在 0.1 至 600MPa、40 至 70°C 和 1 秒至 90 分钟的压力、温度和保持时间范围内，研究了果胶甲酯酶（PME）、多酚氧化酶（PPO）和过氧化物酶（POD）在芒果浆中的失活动力学。酶失活被描述为双过程：在动态升压阶段初始活性变化和随后在等压-等温条件下的下降。前者导致所有三种酶的活性显著增加（p<0.05）；然而，随着所施加的压力-温度强度的增加，增加的活性减少。另一方面，等压-等温条件导致实质性失活（p<0.05），600MPa/70°C/20min 处理最有效地将 PME、PPO 和 POD 的活性分别降低至 32%、15%和 26%。等压-等温条件下的酶失活动力学数据是非线性的，并符合 n 阶反应模型，表明可能由于压力-温度相互作用效应而发生了一系列反应。估计的反应级数 'n' 分别为 0.815、1.106 和 1.137，用于 PME、PPO 和 POD。估计的反应速率常数 k（分钟）表明 PME 是最耐压的酶，其次是 POD 和 PPO。k 的温度和压力依赖性分别用阿累尼乌斯型和艾林型关系表示为激活能和激活体积。提出了一个具有良好实际与预测数据相关性（R>0.90）的经验模型，以模拟等压-等温条件下的酶失活动力学，作为压力和温度的函数。
