【作者】 卫玲玲；

【导师】 应铁进；

【作者基本信息】 浙江大学 ， 食品工程， 2012， 硕士

【摘要】 本文研究了从三种天然优势乳酸菌菌株短乳杆菌(Lactobacillus brevis)、干酪乳杆菌(Lactobacillus casei)、植物乳杆菌(Lactobacillus plantarum)中优选菌种用于制备蔬菜发酵用直投式发酵剂(DVS)的主要影响因素和工艺过程。首先研究了上述三种乳酸菌株单独或复配使用对发酵甘蓝品质的影响。甘蓝接种后,常温条件(约24℃)下发酵3天,监测pH值、总酸、亚硝酸含量、乳酸菌总数的变化情况及感官品质。结果表明按短乳杆菌：植物乳杆菌=1:1复配,总接种量为2-3%,甘蓝泡菜的发酵效果最好。当总接种量为2%时,发酵后泡菜的pH为3.35,总酸为0.74%,乳酸菌活菌数为8.93*107cfu/mL,感官品质也最佳,评分值达到12.1/15.0,亚硝酸盐含量为14.2 mg/kg。然后研究了短乳杆菌、植物乳杆菌的高密度培养,结果表明,短乳杆菌从延滞期到衰亡期的时间为24h,对短乳杆菌影响最大的是初始pH值,pH值较高培养效果较好,接种量影响不大；植物乳杆菌从延滞期到衰亡期的时间为27h,对植物乳杆菌影响最大的是接种量,接种量较小生长较好,初始pH值影响甚小。短乳杆菌比植物乳杆菌更能适应低温环境。在优化的培养条件下,培养密度可达到1.15-1.26*1010cfu/mL最后初步尝试了直投发酵剂的制备工艺。短乳杆菌和植物乳杆菌培养液在4000r/min下离心30min,添加脱脂乳、乳糖、葡萄糖、维生素C、D-山梨醇、L-谷氨酸按照一定比例混合而成的保护剂,通过冷冻干燥,离心回收率分别为：63.9%,74.6%,离心得率分别为：3.75%,3.50%,冻干回收率分别为52.8%,29.4%,冻干得率分别为26.9%,23.0%,冻干粉的活菌密度分别为2.4*109cfu/g,2.74*109cfu/g。按质量比1:1复配后发酵甘蓝泡菜,在常温条件(约24℃),总接种量为1%,发酵3天甘蓝泡菜的发酵效果较好。发酵后泡菜的pH为3.50,总酸为0.89%,乳酸菌活菌数为8.98*107cfu/mL,感官评定也最佳,达到11.6/15.0,亚硝酸盐含量最低为15.6mg/kg。更多还原

【Abstract】 This paper studied the preparation of direct vat starter (DVS) from 3 natural Lactobacillus bacteria Lactobacillus brevis, Lactobacillus casei, Lactobacillus plantarum, for using in vegetable fermentation. The effects of the 3 bacteria as starters individually or combined on the quality of cabbage pickle were investigated. pickle was fermented at room temperature (24℃) for 3 days, with following parameters monitored:pH, titratable acidity(TA), nitrite content, viable cell counts and sensory attributes. Results showed that the combination of Lactobacillus brevis and Lactobacillus plantarum at a ratio of 1:1, with a 2-3% total inoculation had the best effect on fermentation. With the above strains combination and 2% inoculation, the pH reached 3.35, TA reached 0.74%, viable cell counts was 8.93*107cfu/mL, score of sensory analysis was 12.1/15, content of nitrite was 14.2 mg/kg after 3 days of fermentation.Moreover, The high dense cultivation of L.b and L.p was studied. The period between lag phase and decline phase was 24h for L.b, the cultivation of L.b was positively impacted by a higher initial pH, and not affected by the quantity of inoculation. While the period between lag phase and decline phase was 27h for L.p. The cultivation of L.p was better at a controlled quantity of inoculation, but not much influenced by the initial pH. L.b has a better toleration to low temperature than L.p. The dense of L.b and L.p were 1.15*1010to 1.26*1010 cfu/mL by optimization.Finally, the preparation process of DVS was tried out. L.b and L.p were centrifuged at 4000rpm for 30 min, added skim milk, lactose, glucose, VC, D-sorbite, L-glutamic acid with certain ration as protect agent, and freeze-dried. The recovery of L.b and L.p by centrifuging were 63.9% and 74.6%, the yield were 3.75% and 3.50%, recovery of L.b and L.p by freeze-drying were 52.8% and 29.4%, yield were 26.9% and 23.0%. The viable lactobaccilus of DVS were 2.4*109 cfu/g and 2.74*109 cfu/g respectively. The DVS of L.b and L.p were mixed at a ratio of 1:1. It was recommended to inoculate the mixture with 1% at room temperature (24℃) for best quality of pickle fermentation. The fermented pickle had a pH at 3.5,0.89% TA,8.98*107cfu/mL viable lactobaccilus, sensory assessment score at 11.6/15.0, and the lowest nitrite content of 15.6mg/kg (far below the GB upper limit at 40mg/kg).更多还原