【作者】 陆小雪；

【导师】 顾振新；

【作者基本信息】 南京农业大学 ， 农产品加工与贮藏工程， 2008， 硕士

【摘要】 本文从食品原料中筛选出产γ-氨基丁酸(GABA)的乳酸菌株。采用糙米、黄豆芽及脱脂牛奶等营养丰富的天然原料,经酶解处理后作为乳酸菌发酵产GABA的基础培养基,以GABA产量为指标,进行发酵条件优化;将发酵液与果汁复配,制作GABA保健饮料。1、从泡菜和酸奶中分离出产GABA乳酸菌10株,筛选得GABA高产菌株B、BY和SS。3个菌株在含10g/L谷氨酸钠(MSG)的MRS培养基中培养6 d,发酵液中GABA含量分别达到3.680、3.341和2.700g/L。通过16S rDNA基因鉴定和生理生化鉴定,确定菌株B和SS为乳酸乳球菌乳酸亚种(Lactococcus lactis subsp.lactis);菌株BY为唾液链球菌嗜热亚种(Streptococcus salivarius subsp.thermophilus)。2、采用D-最优混料设计对组成乳酸菌发酵培养基的糙米汁、黄豆芽汁及酶解牛奶汁混料比进行优化。结果表明:酶解糙米汁、黄豆芽汁、牛奶汁(可溶性固形物均为4°Bix)混料体积比为33∶62∶5时,发酵液中GABA浓度高达6.43 g/L。3、乳酸菌发酵培养条件优化试验结果表明:MSG添加量对GABA产量和MSG摩尔转化率有显著影响。以GABA产量为5.0 g/L和MSG转化率85%为优化目标,优化出的乳酸菌产GABA的培养条件为:接种量1%、培养温度32.69℃、培养基初始pH 7.05、底物添加量7.32g/L,其最大GABA产量和MSG转化率预测值为5.000g/L和83.2%。在此条件下,乳酸菌发酵过程中发酵液中还原糖、游离氨基态氮、pH值、Glu含量呈下降趋势,可滴定酸和GABA产量呈上升趋势。发酵液中GABA含量在发酵60 h时达最高值。4、采用优化的培养基及发酵条件进行上罐(5 L)发酵,再以此发酵液为原料进行保健饮料研制。优化得到的GABA保健饮料配方为:乳酸菌发酵液5%、枸杞汁40%、苹果汁40%、复合甜味剂3%、磷酸0.10%。用0.25%(W/V)的明胶和0.25%(w/v)的单宁进行澄清后,饮料于室温放置60 d未出现浑浊、沉淀等现象。模糊综合评价表明GABA保健饮料符合消费者的饮用要求。更多还原

【Abstract】 Lactic acid bacteria(LAB) strains producingγ-amino butyric acid(GABA) were isolated from food materials.The GABA-producing strain was cultured in the medium composed of brown rice juice,germinated soybean juice and enzymolyzed skim milk.The ratio of the three kinds of components in the media and culture condition were optimized to increase GABA yield in the broth.Then the fermentation broth was mixed with fruit juice to produce GABA-enriched health drink.1 Ten lactic acid bacteria(LAB) strains producing GABA in culture medium were isolated from pickle and yoghurt.The strain B,BY and SS showed higher GABA-producing ability.Screening results revealed that strain B,BY and SS produced GABA at concentrations of 3.680,3.341 and 2.700 g/L,respectively.Identification tests (i.e.,16S rDNA sequencing and physiological characters) indicated that B and SS belonged to Lactococcus lactis subsp,lactis and BY belonged to Streptococcus salivarius subsp. thermophilus.2 GABA yield of L.lactis B was investigated using brown rice juice,germinated soybean juice and enzymolyzed skim milk(the soluble solids contents were all 4°Bix) through D-optimal mixture design.The results showed that when the mixing ratio of brown rice juice,germinated soybean juice and enzymolyzed skim milk was 33:62:5(v:v:v),the maximum GABA yield of L.lactis B was 6.43 g/L.3 The results of fermentative condition optimization indicated that MSG addition was the most significant factor affecting GABA yield and MSG mole transformation percentage. The optimum condition obtained by RSM for GABA enrichment by L.lactis included the following parameters:inoculation amount 1%,culture temperature 32.69℃,the medium initial pH 7.05 and MSG addition 7.32 g/L.Under this condition,the model predicted a maximum response of 5.000 g/L GABA yield and 83.2%MSG mole transformation percentage.When the strain was cultivated in the above condition,the reducing sugar,free amino nitrogen,pH,Glu content showed increasing tendencies;while titratable acidity and GABA yield showed decreasing tendencies.The GABA yield reached the maximum at the fermentation time of 60 h.4 The pilot-scale research(5 L) was carried out.Then a kind of health GABA-enriched soft drink was developed with the whole liquor from L.lactis B fermentation.Organoleptic assessment was carried out with fuzzy comprehensive evaluation methodology.The results showed that the basic ingredients of GABA-enriched soft drink were:5%fermentation broth,40%medlar juice,40%apple juice,3%compond sweetener,0.10%phosphoric acid.The drink was lauter after clarified with 0.25%gelatin and 0.25%tannin clarification and there was no deposition in the beverage after 2 months storage at the room temperature. Fuzzy comprehensive evaluation methodology showed that GABA-enriched soft drink was acceptable to sensory test members.更多还原