Isolation and characterization of a Lactobacillus helveticus strain with reduced post-acidification

Abstract:

[Objective] Fermented dairy are favored for their excellent nutrition and health functions concomitantly. Post-acidification is caused by the continuous metabolism of active lactic acid bacteria during the process of storage, transportation and sales, which seriously affects its sensory quality and the number of viable strains. This study screened the low-post-acidification Lactobacillus helveticus to resolve the post-acidification of its fermented dairy.[Methods] In this study, Lactobacillus helveticus L551 was used as the original strain. Using neomycin sulfate as the selection pressure select the weakly acidified Lactobacillus helveticus. Comparing the difference of fermentation characteristics between the weakly acidified strain and the original strain.[Results] The acid production rate of weakly acidified Lactobacillus helveticus L551-1 was slowed down. The acid production rate of 7-8 h at 42℃ was 9 °T/h, which was 53% lower than the original strain (19 °T/h); the acidity of fermentation at 42℃ for 24 h was 155 °T, which was 40% lower than that of the original strain (259 °T); the post-acidification of fermented milk was 122 °T stored at 4℃ for 21 days, which was 23% lower than the original strain (158 °T). Using gas chromatography-mass spectrometry (GC-MS) compared the composition and type of volatile flavor compounds in fermented milk of the two strains, and there was no significant difference.[Conclusion] Through neomycin sulfate, the weakly post-acidified Lactobacillus helveticus L551-1 was obtained, which can significantly improve the post-acidification problem of fermented milk, and have a great significance to the development and application of direct starter.

Key words:Lactobacillus helveticus;post-acidification;fermentation properties;fermented dairy;flavor substances