School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China; State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China; Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Guangzhou 510641, China; Overseas Expertise Introduction Center for Discipline Innovation of Food Nutrition and Human Health (111 Center), Guangzhou 510641, China.
School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China.
Food Chem. 2021 Oct 15;359:129887. doi: 10.1016/j.foodchem.2021.129887. Epub 2021 Apr 20.
Although lots of work has reported the structural variations of starch in microwave treatment, most of them are detected in the environment with non-constant microwave power and inhomogeneous heating, and the results are always in poor repeatability. In this study, the equipment with constant microwave power (CPM) and homogeneous heating was designed. And the phase transition of multi-scale structure of rice starch (30% moisture content) caused by CPM treatments with two heating modes, namely rapid microwave heating (RWH) and slow microwave heating (SWH) were investigated systematically. SEM results showed that the surface of starch granules after CPM treatment were rough and broken, and the damage caused by RWH was more distinct than that by SWH. SAXS, XRD and C NMR results revealed that the CPM treatment decreased the degree of crystallinity and content of double helices of starch. Moreover, the influence of RWH on the variation of starch granules was greater than that of SWH, which can be attributed to the intensive friction and collision as well as the rapid evaporation of water in RWH treatment. Specifically, it exhibited greater destruction on the linkage of starch and the internal crystalline region in RWH treatment than SWH treatment, thereby resulting in more obvious damages on the lamellar and morphological structure of rice starch. In conclusion, CPM equipment has improved the problems of uneven heating and poor experimental repeatability. After CPM treated starch, the molecular structure of starch was destroyed, which provides a useful method to modify properties of starch.
尽管已有大量研究报道了微波处理过程中淀粉结构的变化，但这些研究大多是在非恒定微波功率和不均匀加热的环境下进行的，且结果的重复性较差。本研究设计了一种具有恒定微波功率（CPM）和均匀加热的设备。并系统研究了两种加热模式，即快速微波加热（RWH）和缓慢微波加热（SWH）对含水量为 30%的大米淀粉多尺度结构相变的影响。SEM 结果表明，CPM 处理后的淀粉颗粒表面粗糙且破裂，RWH 引起的破坏比 SWH 更为明显。SAXS、XRD 和 C NMR 结果表明，CPM 处理降低了淀粉的结晶度和双螺旋含量。此外，RWH 对淀粉颗粒变化的影响大于 SWH，这归因于 RWH 处理中强烈的摩擦和碰撞以及水的快速蒸发。具体而言，RWH 处理对淀粉的连接和内部结晶区的破坏程度大于 SWH 处理，从而导致大米淀粉的层状和形态结构受到更明显的破坏。总之，CPM 设备改善了加热不均匀和实验重复性差的问题。经 CPM 处理后的淀粉，其分子结构被破坏，为淀粉性质的改性提供了一种有用的方法。
