Abstract: In this study, lipase-producing lactic acid bacteria (LAB) were isolated from traditional fermented foods and screened for their growth characteristics and lactone-producing ability in a fast-ripened cheese slurry model. The selected strains were used as an adjunct starter culture for making Cheddar cheese. Sensory evaluation and gas chromatography-mass spectrometry (GC-MS) were used to compare changes in the flavor and lactone content of Cheddar cheese made with and without an adjunct starter during ripening at 4, 10 or 14 ℃ for up to 150 days. The results showed that Pediococcus acidilactici 4D and Lactococcus garvieae Y3, two strains with the ability to produce lipase, exhibited better lactone production performance. Sensory evaluation showed that compared with Cheddar cheese without adjunct starter, the cheese added with P. acidilactici 4D had the highest milky and fruity aroma intensity after 90 days of ripening at 10 and 14 ℃, respectively. The cheese added with L. garvieae Y3 showed the highest milky aroma intensity after 120 days of ripening at 14 ℃. Four lactones were identified by GC-MS. The contents of δ-decalactone and δ-dodecalactone in Cheddar cheese with P. acidilactici 4D or L. garvieae Y3 were higher than those in Cheddar cheese without adjunct starter at all three ripening temperatures, and both strains could promote the formation of δ-octolactone. In addition, γ-butyrolactone was identified only in cheddar cheese fermented by L. garvieae Y3. By exploring the effects of ripening temperature and time on the formation of lactones, it was found that the optimal ripening temperature was 14 ℃. The total lactone content of cheese added with P. acidilactici 4D reached the highest level at 90 days of ripening, while that with L. garvieae Y3 reached the highest level at 120 days.

Key words: lactic acid bacteria; lipase; Cheddar cheese; lactone compounds; adjunct starter