The characteristics investigation of lactic acid bacteria capable of producing aromatic compounds isolated from traditional yogurt in Zanjan province

Yogurt production by milk fermentation is one of the oldest methods used by humans to convert milk into a product with longer shelf life and better sensory evaluation. This study aimed to investigate the characteristics of lactic acid bacteria isolated from yogurt in Zanjan rural areas and these strains ability in the diacetyl production. This study collected and transferred seven yogurt samples to the laboratory under standard conditions. Then the isolated strains were examined for morphology, several test such as catalase, hemolysis, antibiotic susceptibility, growth rate at different temperatures and yogurt sensory evaluation. The selected yogurt samples were examined for diacetyl production using SPME-GC after bwing stored at 5°C for 14 days. According to the results, the strains were divided into two groups based on morphology: bacilli and cocci. All strains were gram-positive and catalase negative. Most of the studied strains were antibiotic sensitive and shown negetive hemolysis. In the selected yogurt samples L1and N7, the diacetyl production was 5/6,10ppm respectively. The studied strains had high diacetyl production ability and also caused the butter aroma and the traditional Iranian yogurt memory, which leads to the production of yogurts that is more compatible with the Iranian people’s taste.