微波诱导对大米淀粉陈化行为的调控作用和机制研究

The quality of rice changes because of aging phenomenon during storage caused by crystal structure changes of starch. How to effectively control and use the aging behavior of starch become one of the hot pot of present research. Previous studies of our group found that, microwave treatment could induce thermodynamic differentiation of starch, thereby affected the aging behavior of rice. However, the accurate control technology and regulation mechanism of ageing behavior of rice starch induced by microwave was still unclear. Consequently, the microstructure of starch will be chose as the study perspective in this program, and microwave will be used to directionally induce starch with differentiated thermodynamic and molecular structure through the hierarchical recursive method step by step. The aging behavior differences (such as thermodynamic properties and aging rate) will be measured and compared before and after induction, and the parameters (frequency, power, and time, etc.) of microwave which may impact the starch aging behavior will be analyzed to reveal the process of starch properties changes and morphological evolution during induction and aging. At the meanwhile, the molecular structure of starch (long-range and short-range crystal structure and the double helix structure of the starch) and fine structure of starch (the chain length distribution, the degree of polymerization, the number-average and weight-average molecular weight) before and after induction will be characterized. The relationship among the aging of starch and the molecular structure and fine structure of starch will be established by analyzing and constructing the model of complex macromolecular structure of starch. Then, the regulation mechanism of ageing behavior of rice starch induced by microwave will be illustrated, and new technical solutions for controlling and using the aging of starch effectively will be provided.

大米在贮藏过程中由于淀粉等组分结构改变而发生陈化现象，导致产品品质改变；如何有效控制、利用淀粉的陈化行为是当前研究热点。前期发现，微波处理可诱导淀粉产生热力学差异化，进而影响陈化行为，然而微波诱导准确调控淀粉陈化行为的技术尚未成型、调控机制亦不明确。为此，本项目从淀粉微观结构入手，以微波为手段，通过分层次逐步递进法，诱导产生热力学和分子结构差异化淀粉，测定和比较诱导前后陈化行为（热力学特性、陈化速度等）的差异性，对诱导体系中影响淀粉陈化行为的系统参数（频率、功率和时间等）进行分析，揭示微波诱导和陈化期间淀粉性质变化和形态演变的过程；同时，表征诱导前后淀粉分子结构（双螺旋结构、长程和短程晶体结构）和精细结构（链长分布、聚合度、数均和重均分子量）的变化；构建淀粉分子结构变化的模型，揭示淀粉陈化行为与精细结构的关系，阐明微波诱导调控淀粉陈化行为的机制，为有效控制、利用淀粉陈化提供新的技术方案。

大米在贮藏过程中由于淀粉等组分结构改变而发生陈化现象，导致产品品质改变；如何有效控制、利用大米的陈化行为是当前研究热点。本项目从分子微观结构入手，采用微波诱导调控大米陈化行为，构建分子结构变化模型，阐析大米陈化的微波调控机制。主要内容有（1）加温加湿贮藏过程中大米淀粉的微波调控：微波诱导淀粉分子链的剧烈运动解开淀粉链之间的缠结，促进随后的加温加湿贮藏过程中分子链的的重排和相互作用，从而导致大米淀粉的结构和理化性质的变化；（2）贮藏过程中大米陈化的微波调控：微波诱导使大米凝胶的糊化温度和硬度增加，凝胶网络强度增强，凝胶粘度和溶胀力降低，游离脂肪酸降低，晶体结构无明显变化，大米脂类（脂肪酸含量和直链淀粉-脂质复合物）及晶体结构变化与微波诱导无关；（3）大米陈化的微波调控机制：微波诱导促进巯基团的氧化和二硫键的形成，增加了蛋白质凝胶网络强度；导致结合酚酸的释放和游离酚酸含量的增加，增强了细胞壁强度；迫使胚乳微观机械力行为的变化，增加了细胞间的粘附强度；（4）功能性复合粒子及其贮藏稳定性：采用两步pH循环法制备蛋白-壳聚糖盐酸盐复合粒子，进而开发蛋白-壳聚糖的稳定乳液，采用喷雾干燥制备了微胶囊，得到包封率高、复水性能好、氧化稳定性强的产品。项目揭示了大米陈化行为与组分结构的关系，阐析了加温加湿贮藏过程中大米淀粉的微波调节机制，明晰了贮藏过程中大米陈化的微波调控机理，且形成了可提升新采收稻米食味品质的微波调控技术，适合直条米粉原料品质控制的微波加速陈化技术，可延长粮食贮藏期的微波抑制陈化技术，以及用于生产冻融稳定变性淀粉的改性技术等，可在粮食加工与贮藏、直条米粉原料质量控制、淀粉改性等领域应用。