School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
Carbohydr Polym. 2013 Sep 12;97(2):406-12. doi: 10.1016/j.carbpol.2013.05.021. Epub 2013 May 18.
The aim of the present study was to investigate the effect of microwave heating on water distribution and dynamics in starch granules during the gelatinization of starch. Starch samples treated with microwave heating, rapid conventional heating and conventional heating was measured by (1)H NMR to examine the water distribution and dynamics in rice starch granules at a water activity of 0.686. The system proton longitudinal and transverse relaxation times were determined using inversion recovery (IR) and Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences. The results showed that the T₁ of the water molecules in the samples treated with any of the three heating methods exhibited two distinct spectral peaks over the temperature range of 40-60 °C. With rising temperature, the long T₁ component and the short T₁ component approached each other, showing a trend of gradual convergence, while T₂ exhibited a single peak over the entire temperature range examined. In addition, significant differences were observed in the T₁ and T₂ of the water molecules in the samples heated by microwave, rapid conventional and conventional. The results show that the rapid heating effect of microwave inhibits the destruction of the hydrogen bonds between starch and water molecules. In contrast, the vibration motion of polar molecules caused by microwave heating accelerates the destruction of hydrogen bonds, producing a much stronger effect than the rapid heating effect of microwave.
本研究旨在探讨微波加热对淀粉颗粒糊化过程中水分分布和动态变化的影响。通过（1）H NMR 对水活度为 0.686 的大米淀粉颗粒中的水分分布和动态进行了研究，测量了经微波加热、快速常规加热和常规加热处理的淀粉样品。采用反转恢复（IR）和 Carr-Purcell-Meiboom-Gill（CPMG）脉冲序列测定了体系质子纵向和横向弛豫时间。结果表明，在 40-60°C 的温度范围内，三种加热方式处理的样品中的水分子 T₁表现出两个明显的谱峰。随着温度的升高，长 T₁ 成分和短 T₁ 成分逐渐接近，表现出逐渐收敛的趋势，而 T₂ 在整个测试温度范围内表现为单峰。此外，微波、快速常规和常规加热处理的样品中的水分子的 T₁ 和 T₂ 存在显著差异。结果表明，微波的快速加热效应抑制了淀粉和水分子之间氢键的破坏。相比之下，微波加热引起的极性分子的振动运动加速了氢键的破坏，产生的效果比微波的快速加热效应更强。
