Dept. of Biotechnology and Food Engineering, School of Biotechnology and Health, Tecnológico de Monterrey-Campus Monterrey, N.L., México.
J Food Sci. 2010 Aug 1;75(6):S264-70. doi: 10.1111/j.1750-3841.2010.01654.x.
High hydrostatic pressure (HHP) processing improves the shelf life of avocado paste without a significant impact on flavor; however, scarce information is available on biochemical modifications during its extended storage period. The present study focused on the changes in oxidative enzyme activities of pressurized avocado paste (600 MPa for 3 min) during refrigerated storage (45 d at 4 degrees C). Aerobic plate counts (APC), lactic acid bacteria counts (LAB), pH, and instrumental color were also evaluated during storage. Processing with HHP caused a decrease in polyphenol oxidase (PPO) and lipoxygenase (LOX) activities, resulting in residual enzyme levels of 50.72% and 55.16%, respectively. Although instrumental color values didn't change significantly during the evaluated storage period, both enzymes (PPO and LOX) recuperated their activities at 10 to 15 d of storage, reached the original values observed in the fresh paste, and then started a declining phase until the end of the storage period. Pulp pH presented a consistent decline during the first 20 d of storage. LAB counts were very low during storage, discarding lactic acid production as responsible for the observed pH decline. Enzyme reactivation, cell disruption, and a gradual migration of intracellular components such as organic acids are herein proposed as the main mechanisms for the deterioration of HHP treated avocado paste during its refrigerated storage. Practical Application: At the present, HHP is the most effective commercial nonthermal technology to process avocado paste when compared to thermal and chemical alternatives. Although it has proven to be an excellent product-technology match, little information is known on the biochemical changes that take place in the product during its refrigerated shelf life. Biochemical reactions during storage are important, since they can influence avocado paste nutritional and flavor qualities at the time of product consumption. The present study reports for the first time the re-activation of PPO and LOX during storage of avocado paste under commercial and economically feasible processing conditions (600 MPa and 3 min). The reactivation of oxidative enzymes observed in the present study is relevant for future studies on the HHP stability of food systems in general, and it is considered an important finding for the food industry and researchers seeking to deliver products with superior nutritional and flavor characteristics.
高静压（HHP）处理可延长鳄梨酱的保质期而不显著影响其风味；然而，关于其在延长储存期内的生化变化，信息仍然匮乏。本研究集中于在冷藏（4°C 下 45 天）期间研究加压鳄梨酱（600 MPa 处理 3 分钟）的氧化酶活性变化。在储存期间还评估了需氧平板计数（APC）、乳酸菌计数（LAB）、pH 值和仪器颜色。HHP 处理会降低多酚氧化酶（PPO）和脂氧合酶（LOX）的活性，导致残留酶水平分别为 50.72%和 55.16%。尽管在评估的储存期内仪器颜色值没有明显变化，但两种酶（PPO 和 LOX）在储存 10 至 15 天内恢复了活性，达到了新鲜糊状物中观察到的原始值，然后开始下降阶段，直到储存期结束。果肉 pH 值在储存的头 20 天内持续下降。储存期间 LAB 计数非常低，排除了产酸作为导致观察到的 pH 值下降的原因。在此提出酶的重新激活、细胞破裂以及细胞内成分（如有机酸）的逐渐迁移是 HHP 处理的鳄梨糊在冷藏储存期间劣化的主要机制。实际应用：目前，与热和化学替代物相比，HHP 是处理鳄梨糊的最有效商业非热技术。尽管已证明这是一种出色的产品-技术匹配，但对产品在冷藏货架期内发生的生化变化知之甚少。储存过程中的生化反应很重要，因为它们会影响产品消费时鳄梨糊的营养和风味质量。本研究首次报道了在商业和经济可行的加工条件（600 MPa 和 3 分钟）下鳄梨糊在储存过程中 PPO 和 LOX 的重新激活。本研究中观察到的氧化酶的重新激活对于一般食品系统的 HHP 稳定性的未来研究具有重要意义，并且被认为是食品行业和研究人员寻求提供具有卓越营养和风味特性的产品的重要发现。
