微波诱导淀粉自由体积变化的机理及调控

淀粉自由体积是其原子尺度的空洞、分子尺度的空穴以及分子链无规堆砌产生的结构缺陷。在加工过程中，自由体积的变化影响淀粉的玻璃化转变特性，决定淀粉质食品的稳定性和分子流动性。通常调控自由体积的方法主要借助外源小分子和物理剪切等方式，其干预效果受剂量等因素的限制已得到确证。然而，作为典型的多羟基含水原料，淀粉具备介电响应增强和界面极化重排的本征优势，故可采用微波进行调控。本课题拟在淀粉质物料电磁学研究的基础上，借助正电子湮灭等技术，考察自由体积在微波和传导加热中的尺寸、浓度以及分布规律；通过研究微波对淀粉结晶结构和水状态的干预，揭示诱导自由体积变化的结构及热力学基础；通过研究淀粉在不同微波模式和程序化过程中的响应规律，揭示诱导自由体积变化的能量转化基础；通过研究自由体积与玻璃化转变的关系，解析微波调控引发的淀粉抗回生机制。课题研究有助于深入理解淀粉质食品的加工机制，并为微波场技术的应用提供基础。

The free volume in starch refers to holes between atoms, interstitial spaces among starch molecules and structural defects resulting from the random arrangement of molecular chain segments. During food processing, the variation of this free volume would significantly affect the glass transition of starch, thus determining the molecular mobility and stability in starchy food. Usually, the free volume could be regulated using exogenous small molecules or physical shear, and it has been verified that the effect of these methods is limited by factors such as the dose. It is worth noting that starch is a typical polyhydroxy material with intrinsic advantage in terms of dielectric response enhancement and interfacial polarization rearrangement, therefore microwave is herein proposed to regulate the free volume in starch. Based on the electromagnetic research of starchy materials, the size, concentration and size distribution of free volume in starch respectively suffering microwave and conduction heating will be investigated using the positron annihilation life spectrum. This project would explore the effect of microwave on crystal structure of starch and water states to reveal the structure and the corresponding thermodynamics that are responsible for the changes of free volume, and study the response of free volume to microwave in different modes and procedures so as to indicate the background of electromagnetic transformation which causes changes of free volume. Upon the understanding of the relationship between the free volume and glass transition, regulation on the inhibition of starch retrogradation triggered by microwave could be achieved. The completion of our study would be helpful for further understanding the mechanism of starchy-food processing and provide evidence and data for the application of microwave technology in this area.