双菌种混合发酵制备富含γ-氨基丁酸酸奶工艺优化

为提升富含γ-氨基丁酸（gamma-aminobutyric acid，GABA）酸奶中GABA的含量与品质，以脱脂复原乳液为主要原料，以课题组前期筛选的在乳基底物中具备高产GABA潜力的乳酸乳球菌乳酸亚种为发酵剂，以活菌数、GABA产量、L-谷氨酸钠（L-Glu-Na）残留和感官评定等为评价指标，对富含GABA酸奶的发酵工艺进行优化。经单因素实验和均匀试验，推导出双菌种混合发酵脱脂复原乳的模型方程，并确定发酵工艺最优条件。结果表明，复配菌种为干酪乳杆菌；乳酸乳球菌乳酸亚种和干酪乳杆菌复配比例为1:3，发酵时间为48 h，发酵温度为32 ℃，L-Glu-Na添加量为8 g/L；在此最优发酵工艺最优条件下，GABA产量为4.10±0.10 g/L，是优化前的3.78倍。此外酸奶中活菌数为3.03×1010±1.75×1010 CFU/g，酸度值为129.67±2.08 °T，L-Glu-Na残留为0.11±0.01 g/L，各项指标满足GB 19302-2010《食品安全国家标准 发酵乳》中要求，综合感官评分78.42±4.63 分。该工艺有望为更多富含GABA发酵乳制品的开发奠定基础。

Process Optimization of γ-Aminobutyric Acid-rich Yoghurt by Mixing Fermentation with Double Strains

In order to promote the content and quality of γ-aminobutyric acid (GABA) in γ-aminobutyric acid-rich yogurt, defatted reconstituted dairy was taken as the main raw material, Lactococcus lactis subsp. lactis with high-yielding potential of GABA in dairy-based medium selected previously by research group was used as start culture, viable count, yield of GABA, residue of L-Glu-Na and sensory evaluation were taken as evaluation indexes, to carry out research on optimizing the fermentation process of yogurt rich in GABA. Through single factor experiment and uniform experiment, model equation of double-strain mixed fermentation in defatted reconstituted milk was derived, and the optimal fermentation conditions were determined. Results showed that: Compound strain was Lactobacillus casei, proportion of Lactococcus lactis subsp. lactis and Lactobacillus casei 1:3, fermentation time 48 h, fermentation temperature 32 ℃, addition of L-Glu-Na 8 g/L. Finally, the yield of GABA was 4.10±0.10 g/L, which was 3.78 times of that before optimization. In addition, viable count was 3.03×1010±1.75×1010 CFU/g, acidity of yogurt was 129.67±2.08 °T, residue of L-Glu-Na was 0.11±0.01 g/L, all indexes met the requirements of GB19302-2010 National Food Safety Standard Fermented Milk, and the sensory evaluation score was 78.42±4.63. This process would be hopeful to provide a basis for development of more fermented dairy products rich in GABA.