College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China; Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.
Ultrason Sonochem. 2020 May;63:104973. doi: 10.1016/j.ultsonch.2020.104973. Epub 2020 Jan 20.
Modified pectin (MP) was reported to have increased bioactivities compared with the original one. However, traditional modification methods such as using an acidic solvent with heating are not only costly but causing severe pollution as well. In this study, manothermosonication (MTS) with a continuous-flow system was utilized to modify citrus pectin. The citrus pectin (5 g/L) treated by MTS (3.23 W/mL, 400 kPa, 45 °C) exhibited lower molecular weight (Mw, 248.17 kDa) and PDI (2.76). The pectin treated by MTS (400 KPa, 45 °C, 5 min) exhibited a narrower Mw distribution and lowered more Mw (48.8%) than the ultrasound(US)-treated (23.8%). Pectin degradation data fitted well to kinetic model of 1/Mw -1/Mw = kt (45-65 °C). A lower activation energy of 13.33 kJ/mol was observed in the MTS treatment compared with the US-treated (16.38 kJ/mol). The MTS-treated pectin lowered the degree of methoxylation (DM), mol% of rhamnose and galacturonic acid (GalA) while increased mol% of galactose (Gal), xylose (Xyl), and arabinose (Ara). The H and C nuclear magnetic resonance showed that MTS could not alter the primary structures of citrus pectin. However, an elevated (Gal + Ara)/Rha and reduced GalA/(Rha + Ara + Gal + Xyl) molar ratios after MTS suggested that MTS resulted in more significant degradation on the main chains and less on the side chains of pectin, in agreement with the result of atomic force microscope. Moreover, the MTS-treated pectin exhibited a higher 1,1-diphenyl-2picryl hydrazyl radical scavenging capacity compared with original pectin.
改性果胶 (MP) 被报道比原始果胶具有更高的生物活性。然而，传统的改性方法，如使用酸性溶剂加热，不仅成本高，而且还会造成严重的污染。在本研究中，采用连续流系统的机械声化学（MTS）来改性柑橘果胶。用 MTS（3.23 W/mL，400 kPa，45°C）处理的柑橘果胶（5 g/L）表现出较低的分子量（Mw，248.17 kDa）和多分散指数（PDI，2.76）。用 MTS（400 kPa，45°C，5 min）处理的果胶比超声（US）处理的果胶（45-65°C）Mw 分布更窄，Mw 降低更多（48.8%）。果胶降解数据与 1/Mw-1/Mw=kt（45-65°C）动力学模型拟合良好。与超声处理相比，在 MTS 处理中观察到较低的活化能（13.33 kJ/mol）。与 US 处理相比，MTS 处理降低了果胶的甲氧基化程度（DM）、鼠李糖和半乳糖醛酸（GalA）的摩尔百分比，而增加了半乳糖（Gal）、木糖（Xyl）和阿拉伯糖（Ara）的摩尔百分比。氢核和碳核磁共振表明，MTS 不能改变柑橘果胶的一级结构。然而，MTS 处理后（Gal+Ara）/Rha 比值升高和 GalA/（Rha+Ara+Gal+Xyl）摩尔比值降低表明，MTS 处理对果胶主链的降解更为显著，对侧链的降解程度较小，这与原子力显微镜的结果一致。此外，与原始果胶相比，MTS 处理的果胶具有更高的 1,1-二苯基-2-苦基肼自由基清除能力。
