大麦籽粒抗冻蛋白对冻藏面包酵母影响及机制的研究

Decrease of survival rate and vitality of baker's yeast in frozen dough during frozen storage influences the quality of frozen dough and restricts its large-scale applications. This project starts from the quality deterioration of baker's yeast during frozen storage, and the influence of antifreeze protein from barley (BaAFP-1) on baker's yeast during frozen storage and the mechanism was investigated. Systematic study of the influence of BaAFP-1 on baker's yeast during frozen storage would carry on both frozen dough and yeast suspension system. In addition, baker's yeast after frozen storage would isolated and add back to the simulation system and fresh dough to eliminate the influence of gluten deterioration on the gas holding capacity of frozen dough. The aim of this project was to clarify the effect of BaAFP-1 on the thermal properties of these systems during frozen storage; reveal the influences of BaAFP-1 on the formation, recrystallization of ice crystals and water status; clear the effect of BaAFP-1 on the cell membrane characteristics of baker's yeast during frozen storage, including the cell membrane structure and composition, the content of materials inside and outside the cell and the activities of key enzymes; analysis their relationship between these characteristics and the survival rate and vitality of baker's yeast and consequently specify the protection mechanism of the BaAFP-1 during frozen storage. That would be of great significance to elucidate the deterioration mechanism of baker's yeast during frozen storage, improve the quality of frozen dough, and extend the application of antifreeze proteins in the cryopreservation of functional microorganism.

冻藏过程中面包酵母存活率和活力的降低严重影响了冷冻面团的品质和大规模应用。本项目从冻藏过程中对酵母品质劣变，研究大麦籽粒抗冻蛋白（BaAFP-1）对冻藏过程中面包酵母品质的影响及机制。通过冷冻面团和面包酵母悬浮液两种体系系统研究冻藏过程中BaAFP-1对面包酵母冻藏品质的影响，此外通过酵母回添到模拟面团体系和新鲜面团中的方法消除面筋蛋白持气能力对研究结果的影响。旨在明确冻藏过程中BaAFP-1对体系热力学特性变化的影响；揭示BaAFP-1对体系冰晶的形成和重结晶、水分的存在状态的影响；揭示BaAFP-1对面包酵母细胞膜特性包括细胞膜结构和组成、胞内外物质含量及关键酶活性的影响；分析各项指标变化与面包酵母存活率和活力的关系，明确BaAFP-1对冻藏面包酵母品质的影响和作用机制。项目研究对于了解面包酵母冻藏品质劣变机制、提高冷冻面团品质及开拓抗冻蛋白在功能性菌类的低温保存中的应用具有重要意义。

冻藏过程中面包酵母存活率和活力的降低严重影响了冷冻面团的品质和大规模应用。本项目从冻藏过程中酵母品质的劣变出发，系统研究冻藏过程中抗冻蛋白对面包酵母冻藏品质的影响，以明确大麦籽粒抗冻蛋白对冻藏过程中面包酵母品质的影响及机制。项目分别以冷冻面团和面包酵母悬浮液两种体系为载体，通过酵母回添到模拟面团体系和新鲜面团中进行比较的方法消除面筋蛋白持气能力对研究结果的影响。通过对冻藏过程中抗冻蛋白对体系热力学特性变化的影响、水分存在状态的影响、酵母存活率、活性和功能性的影响以及面包酵母细胞膜特性包括细胞膜结构和组成、胞内外物质含量及关键代谢酶活性的影响，分析抗冻蛋白对冻藏酵母品质的影响和作用机制。结果表明浊点萃取法能够显著去除BaAFPs中的杂蛋白，大大提高纯化效率。选择-7℃作为提取液过冷温度，通过冰晶亲和吸附处理能够提高AFPs含量和纯度。BaAFP-1的加入能够显著影响面团及酵母悬浮体系的水分和热力学特性以及酵母存活率和活性，且对酵母悬浮液体系影响更显著。通过酵母回添方式与原始面团比较结果表明冻藏过程中面团品质劣变是酵母品质劣变与面团中面筋蛋白等组分劣变共同作用的结果。对酵母细胞膜结构特性的研究结果表明，冻融循环处理能导致酵母细胞膜流动性降低，破坏酵母主要代谢酶的活性，使酵母细胞膜通透性增大。BaAFP-1的加入能够减缓但不能抑制这种劣变。