Sichuan Key Laboratory of Food Biotechnology, School of Food and Bioengineering, Xihua University, Chengdu 610039, China.
Sichuan Key Laboratory of Food Biotechnology, School of Food and Bioengineering, Xihua University, Chengdu 610039, China.
Ultrason Sonochem. 2020 Oct;67:105144. doi: 10.1016/j.ultsonch.2020.105144. Epub 2020 Apr 27.
This study investigated the effects of high-power ultrasound (HPU, 0-45 °C, 242-968 W/cm, 2-16 min) on the rheological properties of strawberry pulp. Following the HPU treatment, the strawberry pulp exhibited an increase in apparent viscosity, storage modulus (G'), and loss modulus (G″). The water-soluble pectin (WSP), pectin methylesterase (PME) activity, and free calcium ions (Ca) of the strawberry pulp after HPU treatment were investigated to determine a possible reason for this phenomenon. HPU caused a significant decrease in the degree of esterification (DE), molecular weight (Mw), and particle size of strawberry WSP, but no significant changes were evident in the galacturonic acid (GalA) content and the zeta (ζ)-potential (P > 0.05), resulting in decrease in the apparent viscosity. Moreover, the largest reduction of PME activity was 22.6% after HPU treatment at 605 W/cm and 45 °C for 16 min, indicating that the PME was resistant to the HPU treatments. The free Ca content in the strawberry pulp was significantly decreased after exposure to HPU (P < 0.05). The maximal reduction of 52.01% in the free Ca was achieved at 605 W/cm and 45 °C for 16 min. The overall results indicated that the high residual activity (RA) of PME after HPU might induce the low esterification of WSP, while HPU promoted the interaction of free Ca and low-methylated pectin, to form the network structure of Ca-low-methylated pectin, resulting in an increase in viscosity in the complex strawberry system.
本研究考察了高功率超声（HPU，0-45°C，242-968 W/cm，2-16 分钟）对草莓浆流变性质的影响。HPU 处理后，草莓浆表观粘度、储能模量（G'）和损耗模量（G″）均增加。研究了 HPU 处理后草莓浆的水溶性果胶（WSP）、果胶甲酯酶（PME）活性和游离钙离子（Ca），以确定这种现象的可能原因。HPU 导致草莓 WSP 的酯化度（DE）、分子量（Mw）和粒径显著降低，但半乳糖醛酸（GalA）含量和 ζ-电位（P>0.05）没有明显变化，导致表观粘度降低。此外，在 605 W/cm 和 45°C 下处理 16 分钟后，PME 活性最大降低 22.6%，表明 PME 对 HPU 处理具有抗性。草莓浆中的游离 Ca 含量在暴露于 HPU 后显著降低（P<0.05）。在 605 W/cm 和 45°C 下处理 16 分钟时，游离 Ca 的最大减少量为 52.01%。总体结果表明，HPU 后 PME 的高残留活性（RA）可能导致 WSP 的低酯化，而 HPU 促进了游离 Ca 和低甲基化果胶的相互作用，形成 Ca-低甲基化果胶的网络结构，从而导致复杂草莓体系中粘度的增加。
