College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, Zhejiang, China.
J Sci Food Agric. 2013 Jun;93(8):2028-36. doi: 10.1002/jsfa.6011. Epub 2013 Apr 16.
Modified pectin has been found to have various biological activities. The preparation of modified pectin is generally accomplished by either chemical or enzymatic depolymerisation processes, but both methods have several disadvantages. Ultrasound treatment is simple and requires shorter times and lower temperatures than conventional techniques used for processing plant materials. In recent years the application of ultrasound to modify polysaccharides has received increasing attention. The objective of this study was to use ultrasound to modify citrus pectin.
The average molecular weight of citrus pectin decreased under different ultrasonic conditions. The average molecular weight decreased from 464 to 296 kDa after 30 min of sonication. The degree of methylation of citrus pectin changed slightly and its monosaccharide component remained unchanged when high-intensity ultrasound was applied. The reduced (Gal+Ara)/Rha ratio after ultrasonication suggested degradation in the neutral sugar side chains of citrus pectin. Atomic force microscopy results confirmed the degradation of citrus pectin chains by ultrasound at nanolevel.
Ultrasound is an effective way to pretreat or modify pectin. The degradation of citrus pectin is due to the cavitational effects of ultrasound. Thus ultrasound may be useful in establishing environmentally friendly extraction and modification technologies for pectin.
改性果胶具有多种生物活性。改性果胶的制备通常通过化学或酶解聚过程来完成，但这两种方法都有几个缺点。超声处理简单，所需时间和温度均低于用于加工植物材料的常规技术。近年来，超声在多糖改性方面的应用受到了越来越多的关注。本研究的目的是使用超声处理柑橘果胶。
不同超声条件下，柑橘果胶的平均分子量降低。超声 30 分钟后，柑橘果胶的平均分子量从 464 kDa 降低至 296 kDa。当应用高强度超声时，柑橘果胶的甲基化程度略有变化，其单糖组成保持不变。超声处理后（Gal+Ara）/Rha 比值降低表明柑橘果胶中性糖侧链发生降解。原子力显微镜结果证实了超声在纳米级水平上对柑橘果胶链的降解。
超声是预处理或修饰果胶的有效方法。柑橘果胶的降解归因于超声的空化作用。因此，超声可能有助于建立果胶的环保提取和改性技术。
