啤酒酿造过程中泡沫活性蛋白质Z的结构变化对其理化性质的影响

Beer foam quality is one of the important characteristics that a consumer uses to determine beer quality. Protein Z has an important impact on beer foam stability, and it is has been identified as one of foam-positive proteins. At present, the researches about protein Z focus on its detection, evaluation and contribution. Protein Z is glycated in the malting process, and the glycated protein Z was detected in final beer. However, all the study results couldn't completely explain the change regularity of protein Z through the whole beer brewing process. In addition, the structure of protein Z during different brewing stage has not been understood systematacially. The research intends to obtain the protein Z through the separation and purification during brewing process, and then research the changes in secondary structure of protein Z during brewing by using the technology of Circular Dichroism and Infrared Spectrum. Meanwhile, the surface hydrophobicity, heat stability and the physical chemistry index related with beer foam properties will be studied in order to investigate the relationship between changes in the structure of protein Z and the beer foam properties. These studies will be significant for revealing the mechanism of foam stability of protein Z, and supply research theories and ideas for improving beer foam quality and using model protein anticipating of foam performance.

啤酒泡沫是啤酒的重要特征之一，是消费者评价啤酒质量的重要指标。泡沫活性蛋白质Z对啤酒泡沫的稳定性发挥着重要的作用，是啤酒中较完整的泡沫活性蛋白质之一。目前对蛋白质Z的研究多集中在对啤酒泡沫的贡献及其检测与鉴定，并且发现蛋白质Z在制麦过程中发生糖基化修饰，而且在啤酒中发现了其糖基化形式。目前的研究结论尚不能完全解释蛋白质Z在酿造过程中经历了怎样的变化而具有了泡沫性能，没有系统地从蛋白质结构变化这一角度来解释蛋白质Z的特性。本研究拟通过对啤酒酿造过程中蛋白质的分离和纯化得到蛋白质Z，采用圆二色谱技术结合红外光谱技术研究其在酿造过程中二级结构的变化，通过检测其疏水性、热稳定性等和啤酒泡沫相关的关键理化性质指标，探索蛋白质Z结构表征变化对其理化性质的影响，这些研究对阐明蛋白质Z的泡沫稳定性机制有重要意义，同时为寻求预判啤酒泡沫性能或反映酿造过程特点的模式蛋白提供思路。

啤酒泡沫是一种能够直观体现啤酒质量的重要特征，丰富、细腻的泡沫不仅可以给消费者带来较为新鲜的感受，而且可以防止啤酒中风味物质的溢出和啤酒中的物质因空气影响而发生的氧化。影响啤酒泡沫的物质很多，蛋白质作为啤酒中的重要组成部分，对啤酒泡沫的品质起到至关重要的作用。蛋白质Z是啤酒中发现的拥有较高表面粘度和弹性的蛋白质，在酿酒过程中能够抵抗酶解与高温的影响，最终对啤酒泡沫的稳定性与啤酒质量产生影响。目前对于酿造过程中蛋白质Z的结构、理化特性以及对泡沫影响的研究较少，因此研究酿造过程中蛋白质Z的结构和修饰特性对探究其稳定啤酒泡沫的机理有重要意义。本论文建立了啤酒泡沫稳定性评价方法、确定了蛋白质Z与泡沫稳定性的正相关性、分析了酿造过程中蛋白质Z二级结构的变化规律、使用毕赤酵母表达体系获取糖基化修饰的蛋白质Z、对比分析糖基化与糖化修饰对蛋白质Z结构与特性影响，最终确定了对啤酒泡沫稳定性有利的蛋白质Z结构和修饰特性。