College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, Zhejiang 310058, PR China.
Ultrason Sonochem. 2013 Jan;20(1):222-31. doi: 10.1016/j.ultsonch.2012.07.021. Epub 2012 Aug 24.
The effects of ultrasound on the molecular weight of apple pectin were investigated. The structure and rheological properties of the degradation products were also tentatively identified by High Performance Liquid Chromatography-Photodiode Array Detector (HPLC-PAD), Infrared spectroscopy (IR), Nuclear Magnetic Resonance spectroscopy (NMR) and Rheometer. The results indicated that the weight-average molecular weight of apple pectin decreased obviously after ultrasound treatment. The molecular weight of degradation products had a uniform and narrow distribution. Ultrasound intensity and temperature play an important role in the degradation reaction. Degradation kinetics model of apple pectin fitted to 1/M(t) - 1/M(0) = kt from 5 to 45 °C. The degree of methylation of apple pectin reduced according to IR analysis when ultrasound was applied. Ultrasound treatment could not alter the primary structure of apple pectin according to the results determined by HPLC, IR and NMR. Meanwhile, the viscosity of apple pectin was 10(3) times as large as that of ultrasound-treated apple pectin. The ultrasound-treated apple pectin showed predominantly viscous responses (G' < G") over the same frequency range. The results suggested that ultrasound provided a viable alternative method for the modification of pectin.
研究了超声对苹果果胶分子量的影响。通过高效液相色谱-光电二极管阵列检测器（HPLC-PAD）、红外光谱（IR）、核磁共振光谱（NMR）和流变仪初步确定了降解产物的结构和流变性能。结果表明，超声处理后苹果果胶的重均分子量明显降低。降解产物的分子量具有均匀且较窄的分布。超声强度和温度对降解反应起着重要作用。苹果果胶的降解动力学模型符合 5 至 45°C 时的 1/M(t) - 1/M(0) = kt。根据 IR 分析，当施加超声时，苹果果胶的甲基化程度降低。根据 HPLC、IR 和 NMR 的结果，超声处理不会改变苹果果胶的一级结构。同时，苹果果胶的粘度是超声处理的苹果果胶的 10(3)倍。在相同的频率范围内，超声处理的苹果果胶表现出主要的粘性响应（G' < G"）。结果表明，超声为果胶的改性提供了一种可行的替代方法。
