【作者】 于辉；

【导师】 贾英民； 孙宝忠；

【作者基本信息】 河北农业大学 ， 农产品加工及贮藏工程， 2006， 硕士

【摘要】 本课题以国产发酵牛肉Bundnerfleisch自然发酵过程中分离筛选出的三株优势菌——植物乳杆菌、戊糖片球菌和木糖葡萄球菌为研究对象,对菌株部分特性进行了测定,系统研究了菌体细胞增殖条件、浓缩分离条件、冻干菌粉发酵剂冷冻过程中抗冷冻复合干燥剂的配制、成品发酵剂的贮存特性,旨在为低酸发酵肉制品直投式浓缩型发酵剂生产提供依据。研究结果如下: 本文测定了植物乳杆菌、戊糖片球菌和木糖葡萄球菌的部分发酵特性,研究发现:三者均具有较强的耐盐性和耐亚硝酸盐性;植物乳杆菌和戊糖片球菌只具有蛋白降解能力,而木糖葡萄球菌具有蛋白降解能力和脂肪降解能力;植物乳杆菌和戊糖片球菌菌株对致病菌的抑菌效果较好,木糖葡萄球菌抑菌作用较差。 对植物乳杆菌、戊糖片球菌和木糖葡萄球菌的增殖培养基进行了优化,确定了菌株的复合增殖培养基配方。植物乳杆菌的复合增殖培养基配方为:麦芽汁培养基中添加2%乳糖、1%牛肉蛋白胨、2.5%酵母膏、10%番茄汁;戊糖片球菌的复合增殖培养基配方为:麦芽汁培养基中添加0.5%乳糖、1.5%牛肉蛋白胨、5%酵母膏、10%番茄汁;木糖葡萄球菌的复合增殖培养基配方为:麦芽汁培养基中添加0.5%葡萄糖、1.5%牛肉蛋白胨、0.1%牛肉膏、1%NaCl。 同时对菌株的增殖培养条件进行了研究,确定了菌株的培养条件。植物乳杆菌和戊糖片球菌:培养温度为20℃,培养基初始pH值6.5～7.0,培养时间20h,菌体密度可分别达3.75x10⁹cfu/mL和3.68×10⁹cfu/mL:木糖葡萄球菌:培养温度为20℃,培养基初始pH值7.0,培养时间20h,菌体密度可达5.00x10⁹cfu/mL。 对菌体细胞浓缩分离条件进行了选择研究,结果显示:离心方法浓缩菌体的效果明显高于细菌过滤器的浓缩效果,并且采用高转速离心,可以提高浓缩菌体浓缩倍数,有利于菌体细胞富集分离。确定菌体细胞浓缩分离的适宜离心条件为0～4℃、6000rpm离心30min。 以12%的脱脂乳为冻干悬浮基质添加单因子制成冻干保护剂,进行冷冻干燥试验。从试验结果中发现蔗糖、维生素C、甘油和CaCO₃是植物乳杆菌、戊糖片球菌和木糖葡萄球菌的较好单因子保护剂。利用L₉（3⁴）正交试验优化的植物乳杆菌、戊糖片球菌和木糖葡萄球菌的复合冻干保护剂配方分别为:在脱脂乳中添加5%蔗糖、0.5%维生素C、4%甘油、3%CACO₃;脱脂乳中添加4%蔗糖、1%维生素C、3%甘油、2%CACO₃和脱脂乳中添加3%蔗糖、1.5%维生素C、5%甘油、4%CACO₃,可分别使植物乳杆菌、戊糖片球菌和木糖葡萄球菌冷冻干燥存活率达到63.01%、66.20%和70.47%,制备的冻干菌粉发酵剂的活菌数分别为2.62×10¹⁰cfu/g、2.54×10¹⁰cfu/g和2.91×10¹⁰cfu/g。更多还原

【Abstract】 Biotechnological characteristics, high density cultivation, combined cryoprotectants of concentrated cultures production and quality guarantee-time of starts cultures.et al. were studied here systemically with three strains including Lactobacillus plantarum, Pediococcus pentosaceus and Staphylococcus xylosus, which were separated and identified from naturally fermented dried beef-Bundnerfleisch. The results were following:The result of the fermenting characteristics of the strains indicated that three strains have the properties to endure high salt and high nitrite;Lactobacillu plantarum and Pediococcus pentosaceus could affect the decomposition of protein, Staphylococcus xylosus could affect the decomposition of protein and fat;Lactobacillus plantarum and Pediococcus pentosaceus could inhibit the growths of some pathogenic bacteria, but Staphylococcus xylosus couldn’t.The optimum mediums of these three bacteria were obtained. The optimum medium of Lactobacillus plantarum was based on the malt juice medium adding with 0.5% lactose, 1% peotone beef, 5% yeast extract,5% tomato juice;the optimum medium of Pediococcus pentosaceus was based on the malt juice medium adding with 0.5% lactose, 1.5% peotone beef, 5% yeast extract, 10% tomato juice;the optimum medium of Staphylococcus xylosus was based on the malt juice medium adding with 0.5% glocuse, 1.5% peotone beef, 0.1 %beef extract, 1 %sodium chloride.This paper studied the culture conditions of Lactobacillus plantarum, Pediococcus pentosaceus and Staphylococcus xylosus.The culture conditions of Lactobacillus plantarum and Pediococcrs pentosaceus were: cultured temperature 20℃, initial pH value 6.5~7.0, cultured time 20h;the culture condition of Staphylococcus xylosus was: cultured temperature 20℃, initial pH value 7.0, cultured time 20h. After incubation, the viable counts of three strains were 3.75×10~9cfu/mL, 3.68×10~9cfu/mLand 5.00×10~9cfu/mL.The concentrating enrichment conditions were studied and chosen, the results illstruted that the centrifugal effect was better than the bacteria filter;the effect of high rpm was helpful for bacteria’s concentrating, improved the centrifugation concentrating times.The results indicated that the best effect could be obtained at 0~4℃ with 6 000rpm for 30min.Using 12% skimmed milk as suspended substrat, the function of protectors includingsucrose, glycerin was studied. Results suggested that sucrose, Vc, glycerin and CaCO3 had better effects on promoting cell count. According to orthogonal experiment, the optimal combined cryoprotectants of Lactobacillus plantarum, Pediococcus pentosaceus and Staphylococcus xylosus contained the following ingredients were based on the modified skimmed milk adding with 5% lactose, l%Vc, 5%glycerin and 3%CaCC>3;based on the modified skimmed milk adding with 4% lactose, l%Vc, 3%glycerin and 2%CaCC>3;based on the modified skimmed milk adding with 3%lactose, 1.5%Vc, 5%glycerin and 2%CaCO3. The survival of Lactobacillus plantarum, Pediococcus pentosaceus, Staphylococcus xylosus got to 63.01%, 66.20% and 70.47%;the cell suspension in freeze-drying culture starter containing the suitable protector might be lyophilized into the strains with high viability(the number of viable cell 2.62xl010cfu/g, 2.54x1010cfu/g and2.91xl010cfu/g).Measuring of quality guarantee-time: Storage effect under freezing condition and refrigeration condition was superior to those under indoor temperature, but the contrast was smallness.The prepared solid fermentation agents are stored under refrigeration condition for six months.更多还原