面团冻藏过程中淀粉性质的变化及其与面团品质劣变的关系

Wheat starch is the largest fraction of solids in dough, comprising about 75% in wheat flour. However, Studies focus on the freezing-induced changes for wheat starch granules in the frozen dough are limited. Research will be based on the studies about physico-chemical changes of wheat gluten and separately wheat starch induced by frozen storage, which had been investigated by the applicant. In this proposal, the changes in morphology, chemical content, molecular weight and crystallinity of wheat starch extracted for frozen dough with different freezing storage will be analyzed respectively. Then, the changes in gelatinization, pasting behavior and thermogravimetric analysis for the extracted wheat starch will be also evaluated. Next step to analyze the properties of reconstituted dough with different storage periods, which the frozen starch including A-type starch and B-type starch will be replaced by the unfrozen starch or correspondingly A/B type starch. The evaluation of dough properties will be focused on by the following instruments: farinograph, extensograph, rheometer, rheofermentometer, fourier transform infrared and circular dichroism spectroscopies. The baking response of the correspondingly reconstituted dough will be also determined, such as the appearance, volume, crust color, texture and crumb structure. This research try to understand the rules of changes on physic-chemical characteristics of wheat starch in frozen dough and find the relationship between deterioration of frozen dough and its starch. All these will be beneficial to clarify the essence of deterioration of wheat dough in frozen storage and to improve the quality of frozen dough by suitable and specific methods.

基于小麦淀粉约占面粉质量分数75％，是面团的主要成分，而冷冻面团冻藏过程中淀粉性质变化及其对面团品质影响的研究缺失，本项目以申请人前期就小麦面筋蛋白在冻藏过程中品质劣变以及淀粉冻藏过程中性质变化的研究为基础，以冷冻面团为研究对象，通过分析不同冻藏期淀粉的颗粒形貌、基本组成、分子量分布和晶体结构等特点，获得小麦淀粉在面团冻藏过程中分子结构的变化规律；通过对比不同冻藏期这些淀粉的糊化、黏度及热分解等特性的差异来阐述面团冻藏过程中小麦淀粉热特性变化的规律；在此基础上，采用重组面团方法，以未冻藏淀粉或A、B淀粉分别替换不同冻藏期面团中相应组分，探讨重组面团的粉质、发酵、面筋和微观结构，以及面包的形状、比容、色泽、质构和组织纹理等特性，由此阐明冻藏过程淀粉性质变化及其变化对冷冻面团和面包品质的影响。研究有利于进一步了解冷冻面团品质劣变的本质，为探究合理延缓冷冻面团品质劣变的方法提供理论指导。

冷冻面团会在贮藏过程中发生品质劣变。作为面团最主要成分的小麦淀粉（约占面粉质量分数75%），它在冻藏过程的性质变化及对冷冻面团和最终产品品质的影响的决定性淀粉类型尚未阐明。随着面团冷冻时间的延长，淀粉颗粒中溶出物质量增加，表面形态破坏增大、相对结晶度增加，回生黏度增加。与粒径较大的A-型淀粉颗粒相比，较小粒径的B-型淀粉颗粒理化性质受冷冻影响更大。8周冷冻后B-型淀粉颗粒的劣变对全小麦淀粉短程有序度的增加贡献最大，为74.59%；A-型淀粉颗粒的冷冻变化对全小麦淀粉结晶度(71.92%)与热焓值增加的贡献更大。冻藏过程中小麦淀粉性质变化对面团粉质特性的影响要大于面筋，而流变学特性则相反。在冷冻面团中B-型淀粉颗粒的冷冻变化比A-型淀粉颗粒冷冻对面筋网络、面筋二级结构、流变学特性、可冻结水含量的影响更大。小麦淀粉在冻藏过程中的性质变化对冷冻面团面包的比容、老化速率具有较大影响。其中A-型淀粉颗粒是面包中小麦淀粉回生的主要原因，在冷冻面团面包老化过程中起着至关重要的作用。面粉中A-型淀粉颗粒和全小麦淀粉比例提高对冷冻面团面包比容会产生负面影响，而B-型淀粉颗粒比例提升则会起到正面作用。本课题研究面团冻藏过程中小麦淀粉的结构和功能性质变化规律以及淀粉性质变化与冷冻面团品质劣变的相关性，为完善冷冻面团品质劣变的机理，寻找有效延缓冷冻面团劣变的解决方法，实现冷冻面团品质的可控性提供理论依据。