优质奶啤乳源酵母菌的筛选及其活性干粉制备的研究

发布时间：2017-12-28 19:08

本文关键词：优质奶啤乳源酵母菌的筛选及其活性干粉制备的研究　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：奶啤是一种经乳酸菌、酵母菌两步发酵制成的有益于人类健康的新型乳饮料,属国内外首创。酵母菌是奶啤发酵的关键菌种,能为奶啤提供醇、酸和酯等主要风味物质。但目前采用市售酿酒酵母生产的奶啤产品,无论是在风味上还是在口感上,都不足以满足消费者多样性的需求;部分企业采用筛选后的优质奶啤酵母菌发酵,改善了奶啤的质量,却缺乏此类酵母菌的活性干粉,不利于奶啤产业的长期发展。因此,近年来,奶啤饮料的研究热点逐渐转为优质酵母菌的筛选及其活性干粉的制备问题。本课题首先从开菲尔粒中分离筛选出了一株优质的奶啤发酵乳源酵母菌,并对其种属进行了鉴定,为活性菌粉的制备提供了优质的菌种。然后以摇瓶发酵为基础,采用单因素、BBD(Box-Behnken Design)和正交试验的方法,研究了该酵母菌的最佳培养基组成和最适培养条件,为活性干粉的制备提供高浓度的菌体。最后对真空冷冻干燥法制备活性干粉进行了研究,为优质奶啤乳源活性干酵母的工业化应用提供了基础。论文主要实验结果归纳如下:1.筛选到了一株优质的奶啤发酵乳源酵母菌。以西藏、新疆、黑龙江等地区的新鲜开菲尔粒作为菌种分离源,分离得到了17株纯种乳源酵母菌。分别从发酵样品的理化数据、微生物数;酵母菌的遗传稳定性;发酵样品的感官风味;发酵样品的理化、感官和风味结果的主成分分析这4个方面,逐步进行酵母菌的筛选。结果表明MJ1菌株发酵的样品整体风味最佳,适于奶啤发酵,经5.8S rDNA分子生物学鉴定为马克思克鲁维酵母(Kluyveromyces marxianus)。2.优化了马克斯克鲁维酵母菌MJ1的增殖培养基组成和培养条件。通过单因素和响应面设计对培养基成分进行了优化,得到增殖培养基最佳成份是蔗糖66.37 g/L,酵母粉28.3 g/L,玉米浆15.61 g/L,KH2PO4 4.13 g/L,MgSO40.3 g/L;利用正交设计得到MJ1的培养条件为30℃、160 r/min、初始pH 6.0。3.确定了真空冷冻干燥法制备MJ1活性干粉的条件,得到了真空冷冻干燥保护剂的最佳配方。在真空冷冻干燥过程中,通过比较MJ1菌体的离心收得率,得到了离心的最佳条件6000 r/min,15 min;真空冷冻干燥24 h时,MJ1冻干粉的含水率为2.9±0.08%;单因素和正交试验确定的最佳保护剂组合为5%蔗糖,5%甘露醇,7.5%脱脂乳粉,此条件下所得干粉冻干存活率为74.63±1.17%;-20℃比4℃条件更适宜存放马克斯克鲁维酵母菌活性干粉;活性干粉的发酵活性稳定,发酵产生的奶啤样品在风味和口感上都能得到很好的保证。
[Abstract]:Milk beer is a new type of milk beverage, which is made by two steps of lactic acid bacteria and yeast, which is beneficial to human health. It is the first creation at home and abroad. Yeast is the key strain of milk beer fermentation. It can provide the main flavor substances such as alcohol, acid and ester for milk beer. But the present commercially available yeast production of milk beer products, either in flavor or taste, are not enough to meet consumer diversity demand; some enterprises with high-quality milk beer yeast fermentation after screening, to improve the quality of milk beer, but the lack of such active dry powder yeast, is not conducive to long-term the development of dairy industry. Therefore, in recent years, the research hotspot of milk beer has gradually changed to the selection of high quality yeast and the preparation of active powder. In this project, we first isolated and screened a high quality Ruyuan beer yeast from Phil seed and identified its species, which provided excellent strains for the preparation of active bacteria powder. Then, based on shake flask fermentation, single factor, BBD (Box-Behnken Design) and orthogonal test methods were used to study the optimum medium composition and optimal culture conditions of this yeast, providing high concentration of bacteria for the preparation of active dry powder. Finally, the preparation of active dry powder by vacuum freeze drying was studied, which provided a basis for the industrial application of high quality milk beer Ruyuan active dry yeast. The main results of this paper are summarized as follows: 1. a high quality milk beer fermented Ruyuan yeast was screened. 17 strains of pure Ruyuan yeast were isolated from fresh Phil particles in Tibet, Xinjiang, Heilongjiang and other regions. Yeast selection was gradually done from 4 aspects: physical and chemical data, microbial number, genetic stability of yeast, sensory flavor of fermented samples, physicochemical, physical and sensory analysis results, and principal component analysis. The results showed that the MJ1 strain fermented samples had the best overall flavor, suitable for milk beer fermentation, and identified by Max Clewett M rDNA molecular biology as Kluyveromyces (Kluyveromyces marxianus). 2. optimization Marx Kluyveromyces MJ1 proliferation culture medium and culture condition. Through the single factor and response surface design to optimize the composition of culture medium, get the best multiplication medium ingredient is 66.37 sucrose g/L, yeast powder 28.3 g/L, corn syrup 15.61 g/L, KH2PO4 4.13 g/L, MgSO40.3 g/L; using orthogonal design culture conditions of MJ1 is 30 DEG C, 160 R /min, initial pH 6. 3. the conditions for the preparation of MJ1 active powder by vacuum freeze drying were determined, and the best formula of the vacuum freeze-drying agent was obtained. In the vacuum freeze drying process, through the comparison of MJ1 centrifugal cell yield, the optimal conditions of centrifugation 6000 r/min, 15 min; 24 h vacuum freeze drying, water MJ1 freeze-dried powder rate was 2.9 + 0.08%; the optimum combination of protective agent to determine the single factor and the orthogonal experiment of 5% sucrose, 5% mannitol 7.5%, skim milk powder, the powder obtained under this condition, the survival rate of freeze-dried was 74.63 + 1.17%; -20 C is more suitable for storing Marx Kluyveromyces active powder than 4 DEG C; fermentation activity stable active dry powder, produced by fermentation of milk beer samples in flavor and mouth feeling can get a good guarantee.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS201.3

【参考文献】