【作者】 刘冬；

【导师】 叶明；

【作者基本信息】 合肥工业大学 ， 农产品加工与贮藏工程， 2011， 硕士

【摘要】 本文利用青春双歧杆菌ys01和干酪乳杆菌ys05混合培养富硒,并以其制备富硒酸奶发酵剂。以单因素试验和中心组合试验对富硒酸奶发酵条件进行优化,并考察其理化性质在冷藏期间的变化。结果表明,青春双歧杆菌ys01和干酪乳杆菌ys05混合菌体中硒含量为551μg/g,以其制备的富硒酸奶发酵剂具有良好的发酵性能。富硒酸奶的最佳发酵条件为：奶粉12%、蔗糖5%、低聚异麦芽糖1%、亚硒酸钠61.8μg/kg、酪蛋白酸钠1.4%,接种量4.5%、发酵温度40℃、发酵时间7h。在该条件下,富硒酸奶酸具有良好的感官品质,其理化指标符合GB19302的相关规定,有机硒含量为29.2μg/kg。在25天储藏过程中,富硒酸奶的pH和乳酸菌数,蛋白质、脂肪和非脂乳固体含量均呈下降趋势,有机硒含量相对稳定。以青春双歧杆菌ys01、德氏乳杆菌保加利亚亚种1.1480和嗜酸乳杆菌ysh2混合培养富锌,用富锌的混合菌体制备富锌酸奶发酵剂。通过单因素试验和Box-Behnken试验对富锌酸奶的发酵条件进行优化,并考察其理化性质在冷藏期间的变化。结果表明,青春双歧杆菌ys01、德氏乳杆菌保加利亚亚种1.1480和嗜酸乳杆菌ysh2混合菌体中锌含量为550gg/g,以富锌混合菌体制备的富锌酸奶发酵剂有良好的发酵性能。富锌酸奶的最佳发酵条件为：奶粉13%、蔗糖6%、葡萄糖酸锌39.1mg/kg、变性淀粉1.3%,接种量4.2%、发酵温度41℃、发酵时间6h。在此条件下,富锌酸奶感官总分为8.9,其理化指标符合GB19302的相关规定,有机锌含量为6.2mg/kg。在冷藏过程中,富锌酸奶的pH、乳酸菌数,蛋白质、脂肪和非脂乳固体和有机锌的含量均呈下降趋势,而脱水收缩值呈增加趋势。在复原乳中添加2%、4%和8%(w/v)的老鹰茶,接种青春双歧杆菌ys01、德氏乳杆菌保加利亚亚种1.1480、干酪乳杆菌ys05、嗜热链球菌ys14和嗜酸乳杆菌ysh2制备老鹰茶酸奶,并考察老鹰茶对酸奶的乳酸菌数、风味物质和其他性质的影响。结果表明,老鹰茶对酸奶的脱水收缩值和pH无显著影响,但增加了酸奶的粘度,此外还促进了嗜热链球菌、嗜酸乳杆菌和干酪乳杆菌的生长。在老鹰茶酸奶中,共检测出30种风味物质,主要为醛、酮、酸和醇类。另外,与对照相比老鹰茶酸奶中的部分醛、酮和酸类等风味物质有不同程度的增加。以四氧嘧啶诱导正常小鼠,建立糖尿病小鼠模型,评价富硒、富锌和老鹰茶酸奶对糖尿病小鼠的降血糖作用。结果表明,富硒和富锌酸奶能抑制糖尿病小鼠血糖值增加,而老鹰茶酸奶具有较好的降血糖效果。更多还原

【Abstract】 In this paper, Bifidobacterium adolescentis ys01 and Lactobacillus casei ys05 in the form of mixed culture were used to enrich selenium (Se), and applied them to produce Se-enriched yogurt starter. Then the fermentation conditions of Se-enriched yogurt were optimized by single-factor and central composite design experiments. The changes of physicochemical properties of Se-enriched yogurt were investigated during refrigerated storage. The results showed that the content of selenium in B. adolescentis ys01 and L. casei ys05 was 551μg/g, and Se-enriched yogurt starter had good fermentation performances. The optimal fermentation condition of Se-enriched yoghurt was as follows:milk powder 12%, sucrose 5%, isomaltooligosaccharide 1%, sodium selenite 61.8μg/kg, sodium caseinate 1.4%, inoculum 4.5%, fermentation temperature 40℃, culture time 7h. Under this condition, Se-enriched yogurt had a good sensory quality, physicochemical parameters conformed to the relative requirements in national standard GB19302 and the content of organic selenium was 29.2μg/kg. During 25 days’ storage, the main properties of Se-enriched yogurt including lactic acid bacteria, pH, protein, fat and non-fat milk solid declined, while the content of organic selenium was relatively stable.Bifidobacterium adolescentis ys01, Lactobacillus delbrueckii subsp bulgaricus 1.1480, and Lactobacillus acidophilus ys2 in the form of mixed culture were used to enrich zinc (Zn), and then utilized the mixed cells to produce Zn-enriched yogurt starter. The fermentation conditions of Zn-enriched yoghurt were optimized by single-factor and Box-Behnken design experiments. Then changes of physicochemical properties of Zn-enriched yogurt were investigated during refrigerated storage. The results indicated that the content of zinc in mixed cells was 550μg/g, and Zn-enriched yogurt starter had good fermentation performances. The best fermentation condition of Zn-enriched yoghurt was as follows:milk powder, sugar, zinc gluconate, modified starch, inoculum, fermentation temperature, fermentation time was 13%,6%,39.1mg/kg,1.3%,4.2%,41℃,6h, respectively. With this understanding, the sensory score was 8.9, physicochemical parameters conformed to the relative requirements in national standard GB19302 and the content of organic zinc was 6.2mg/kg of the yoghurt. During refrigerated storage, the pH and the number of lactic acid bacteria, protein, fat, the non-fat solid and organic zinc of the Zn-enriched yoghurt had a decrease trend, but the syneresis increased.The reconstituted milk was added with hawk tea of 2%,4%and 8%(w/v), and inoculated with B. adolescentis ys01,L. bulgaricus 1.1480,L. casei ys05, S. thermophilus ys14 and L. acidophilus ys2 to obtain hawk tea yoghurts. Effects of hawk tea on lactic acid bacteria and flavor, and other qualities of yoghurt were investigated. Results suggested hawk tea had no significant effect on the syneresis and pH of the yoghurt, but increased the viscosity. Hawk tea promoted the growth of the Streptococcus thermophilus, Lactobacillus acidophilus, and Lactobacillus casei. Thirty kinds of flavour components were identified in the hawk tea yoghurt, and majority were aldehydes, ketones, acids and alcohols. Moreover, some of aldehydes, ketones, acids in the hawk tea yoghurt increased to varying degrees, comparing with the control.Diabetic mice model was established with alloxan, and hypoglycemic effects of Se-enriched yoghurt, Zn-enriched yogurt, and hawk tea yogurt were assessed. Results indicated that Se-enriched and Zn-enriched yogurts could prevent blood glucose increasing, whereas hawk tea yogurt had hypoglycemic effect on diabetic mice.更多还原