基于“温度—真空度—水分”互作的水分运动抑制热包装馒头淀粉老化机理

Starch retrogradation, as the key factor for the coarse mouthfeel and short shelf-life of man-tou and other flour based food products has not yet been systematically investigated in previous research. Results from our preliminary studies showed that hot packaging could maintain man-tou’s freshness for a long storage time at room temperature; at the meantime water in man-tou would evaporate in the package while temperature rises and would be absorbed by man-tou while temperature falls. The water movements could play an important role in delaying starch retrogradtion significantly. Therefore in the proposed project, multi-techniques including vacuum determine, DSC, NMR, X ray diffraction, texture analyzer, and sensory analysis will be used in this study to explore the following mechanisms during the hot packaging of man-tou: 1) thermodynamic model of water-vapor phase change, 2) moisture dynamic model, 3) combined water-starch state evolvement rule of hot packaged starch and mantou samples, 4) sensory and in-vitro digestibility evaluation, as well as, 5) develop a novel model for illustrating the temperature-vacuum-moisture interaction effects on starch retrogradation, and the effects of moisture movements on starch recrystallization’s nucleation mode, retrogradation rate, crystalline nature and spatial conformation, and to reveal the regulating mechanisms of moisture movements pattern under packaging environment (i.e., moisture-starch combinet, moisture-vapor phase change, and moisture diffusion mode). Successful delivery of the proposed project would not only provide novel and useful theoretical foundation for modernization of Chinese traditional steamed products, but also would be beneficial to supplement the relevant theory of starch retrogradation.

淀粉老化是导致馒头等传统面制品口感变差和保鲜期缩短的主要原因；本实验室研究表明热包装能实现馒头常温长期保鲜；环境温度升高能使馒头中水分在包装袋内形成水蒸汽，温度降低水蒸汽重新被馒头吸收，与常规包装馒头相比，这种水分运动显著延缓淀粉老化，但深层次原理还不清楚。项目以中国传统食品—馒头为研究对象，利用真空度检测、NMR、DSC、品质分析、体外模拟消化等分析技术，研究①热包装馒头水—汽相变热力学模型，②热包装馒头水分动态变化模型，③热包装淀粉及馒头淀粉的水—淀粉结合态演变规律，④热包装馒头感官及体外消化，⑤构建温度—真空度—水分互作影响淀粉老化动力学模型，阐明水分运动对淀粉老化重结晶成核方式、回生速率、晶体性质及空间构象的影响，揭示包装环境下水分运动模式（水—淀粉结合、水—汽相变、水分扩散）调控淀粉老化的机理。本项目为馒头等中华传统主食的现代化生产提供理论基础，对补充淀粉老化相关理论有重要意义。

馒头是人们日常主食之一，热包装能实现馒头常温长期保存，但馒头贮藏过程中淀粉老化和水分动态变化直接影响馒头品质。本课题探讨了不同包装方式（散装、真空包装、热包装）、不同包装温度（50℃、70℃、90℃），以及不同添加物（燕麦粉、燕麦β-葡聚糖、沙蒿多糖（ASKP）、沙蒿高分子量多糖（60P）、沙蒿低分子量多糖（60S）、小麦淀粉、谷朊粉）等方式处理对馒头在常温贮藏过程中水分分布、淀粉老化特性以及馒头品质变化的影响。研究结果表明：（1）热包装延缓自由水含量降低，馒头淀粉老化结晶度和DO值最小，使得馒头保持较好的品质；（2）包装温度越高馒头，贮藏过程中水分含量越高，硬度越小，淀粉结晶度越小，淀粉形成的晶体结构越疏松，可以延缓馒头淀粉老化；（3）沙蒿多糖（ASKP）和沙蒿高分子量多糖（60P）可促进馒头淀粉短期老化，抑制长期老化，添加量在0.1%-0.5%范围时，添加量越多，抑制老化效果越好，沙蒿低分子量多糖（60S）可以抑制小麦淀粉短期和长期老化；（4）燕麦粉可延缓馒头贮藏过程中的水分散失，燕麦β-葡聚糖可以显著延缓馒头硬度和淀粉有序结构的增加，添加量越高效果越显著，还可引起面筋蛋白中 β-折叠和有序二级结构比例减小，无序二级结构比例增大；（5）添加10%小麦淀粉可增加馒头白度，弱结合水和自由水的相对含量，降低老化淀粉结晶度和晶体增长速率以及淀粉有序结构，对比容没有影响；（6）谷朊粉可以增加弱结合水、自由水的结合强度和相对含量，添加1%的谷朊粉，可增加馒头弹性，降低硬度、咀嚼性和回复性，降低馒头蛋白质的α-螺旋和无规则卷曲比例，增加β-转角和 β-折叠比例，使得蛋白质的螺旋化、无规则卷曲向转角及折叠转化，蛋白质分子结构更为紧密，趋向于稳定。本研究探讨了热包装环境下水分运动调控淀粉老化的机理，回答了密闭环境下馒头水分动态变化模型，分析了“温度—真空度—水分”互作抑制淀粉老化的机理，为实现馒头工业化生产过程中的精准品质控制，开发高品质杂粮馒头提供理论基础。