高产甾醇热带假丝酵母发酵工艺优化及富含甾醇调制乳的制备

Optimization of fermentation process of high-yield sterol Candida tropicalis and preparation of sterol-rich modified milk

该研究以脱脂奶粉及核桃油为主要原料,以高产甾醇热带假丝酵母(Candida tropicalis)1253、保加利亚乳杆菌(Lactobacillus bulgaricus)及嗜热链球菌(Streptococcus thermophilus)为发酵菌种制备甾醇冻干粉,并在此基础上研制富含甾醇调制乳。以甾醇产量为评价指标,通过单因素试验和响应面试验优化菌株1253发酵工艺,对富含甾醇调制乳品质和营养进行综合性评价,并分析其关键差异代谢物及代谢通路。结果表明,最佳发酵工艺为培养时间97 h,培养温度30℃,菌种接种量9.5%,核桃油添加量4%。在此优化条件下,甾醇产量为0.90 mg/g。富含甾醇调制乳感官评分为(86.44±2.06)分,甾醇含量为(22.7±0.6)mg/g。吡哆醛、胆甾醇、γ-氨基丁酸(GABA)、麦角甾苷和柠檬酸等关键差异代谢物通过富集维生素B6代谢、磷酸戊糖途径、乙氧基化物和二甲酸酯代谢、果糖和甘露糖代谢和柠檬酸循环等途径形成特征风味。

In this study,using defatted milk powder and walnut oil as main raw materials,the freeze-dried sterol powder was prepared with high-yield sterol Candida tropicalis 1253,Lactobacillus bulgaricus and Streptococcus thermophilus as fermentation strains.On this basis,the sterol-rich modified milk was prepared.Using sterol yield as evaluation index,the fermentation process of strain 1253 was optimized by single factor tests and response surface tests.The quality and nutrition of sterol-rich modified milk was evaluated comprehensively,and the key differential metabolites and metabolic pathways were analyzed.The results showed that the optimum fermentation technology was culture time 97 h,temperature 30℃,inoculum 9.5%,walnut oil addition 4%.Under the optimized conditions,the sterol yield was 0.90 mg/g.The sensory score of sterol-enriched modified milk was(86.44±2.06)and the sterol content was(22.7±0.6)mg/g.Key differential metabolites such as pyridoxal,cholesterol,gamma-aminobutyric acid(GABA),acteoside and citric acid formed the characteristic flavors through enrichment of vitamin B6 metabolism,pentose phosphate pathway,ethoxylate and dicarboxylate metabolism,fructose and mannose metabolism,and citric acid cycle.