Study on flavor compounds in milk fermented by Lactococcus lactis ssp. Lactis biovar diacetylactis | 乳酸乳球菌乳亚种丁二酮变种发酵乳风味物质研究

صينى. 研究发酵过程中乳酸乳球菌乳亚种丁二酮变种发酵乳双乙酰的变化规律，并检测发酵乳样品中风味物质的种类和含量。采用邻苯二胺法，分别测定25，30 ℃培养4，8，12，24，36和48 h发酵乳中双乙酰的含量，用GC-MS方法测定了发酵乳中挥发性风味物质的组成。乳酸乳球菌乳亚种丁二酮变种发酵前期有大量双乙酰积累，随着发酵时间的延长，双乙酰含量逐步增加。通过GC-MS方法在发酵乳挥发性风味物质中共鉴定出19种成分，其中酯类4种、醇类1种、杂环化合物1种、短链挥发性脂肪酸5种、羰基化合物8种。乳酸乳球菌乳亚种丁二酮变种发酵乳中，有较高含量的双乙酰，在发酵后期其含量更大，乙醇、2,3-_丁二酮、2,3-戊二酮含量也明显高于其他单菌种乳酸菌发酵乳中的相应含量。

إنجليزي. The Changes of diacetyl in milk fermented by Lactococcus lactis spp. Lactis biovar diacetylactis during fermentation were studied. Volatile flavour compounds in the fermented milk were separated and detected. The diaminobenzidine method was used to decide the concentration of diacetyl in fermented milk cultured in 25 or 30℃ for 4, 8, 12, 24, 36 and 48 hours respectively. GC-MS method was used to assess the identification and contents of volatile flavor compounds. There were plenty of metabolized diacetyls in early fermentation. Along with the prolonging of fermented time, the contents increased, and the rates of metabolizing diacetyl accelerated obviously. At the same time, the research identified 19 kinds of flavor compounds, including 4 kinds of esters, ethanol,α-furan formaldehyde,5 kinds of short linked fatty acids,8 kinds of carbonyls with GC-MS. There were high level diacetyl contents, higher in the later stage of fermentation. Furthermore, the contents of ethanol, 2, 3-butanedione and 2,3-pentanedione in the milk fermented by Lactococcus lactis spp. Lactis biovar diacetylactis were higher than the contents in corresponding milk fermented by other single lactic acid bacteria.