微波诱导淀粉自由体积变化的机理及调控

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.

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。

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。淀粉作为典型的多羟基原料，其水合体系受热响应较快，并且具备微波介电响应增强和界面极化重排的本征优势，故可采用微波对淀粉自由体积进行调控。本研究在明确淀粉质物料电磁学特性的基础上，借助正电子湮灭等技术，考察了在微波和传导加热中淀粉自由体积变化，发现微波及传导加热均能影响淀粉自由体积尺寸、浓度以及分布规律，且影响程度存在差异性；研究了微波对淀粉结构和水状态的干预，发现微波能影响淀粉体系水分含量以及水分布状态，进而调控淀粉自由基、结晶结构以及片层结构等系列精细结构，从而揭示了诱导自由体积变化的结构及热力学基础；研究了淀粉在不同微波模式和程序化过程中的响应规律，发现淀粉自由体积随着微波处理功率或时间的增加降低；初步探究了淀粉自由体积与玻璃化转变的关系，发现淀粉玻璃态转变温度与自由体积浓度呈现显著负相关，从而为解析微波调控引发的淀粉抗回生机制提供理论依据。课题研究有助于深入理解淀粉质食品的加工机制，并为微波技术更好的服务于食品加工和保藏提供理论依据。执行期内已完成项目的任务要求和约束性指标，发表国内外学术论文13篇；申请专利4项，其中，已授权3篇。