Analysis of volatile flavor compounds in fermented milk by solid phase microextraction-gas chromatography-mass spectrometry and electronic nose

Abstract:

[Background] Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus are commonly used as yogurt starters, which are widely used in dairy production. [Objective] Based on the previous study, the compound starter with good flavor was screened out (1:100). L. delbrueckii subsp. bulgaricus IMAU20312 and S. thermophilus IMAU80809, and the dynamic variation of flavor compounds in cow milk during the fermentation and storage was analyzed. The result is expected to lay a basis for the development and application of related starters. [Methods] We employed solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and electronic nose to detect and analyze the dynamic changes of the volatile flavor compounds in milk during fermentation and storage. [Results] A total of 23 acids, 13 aldehydes, 15 alcohols, 18 ketones, 11 esters, and 22 alkanes were produced in the fermentation and storage of milk. According to odor activity values (OAV), there were two key flavor compounds (OAV≥1) in the fermented milk. Moreover, other compounds such as 1-octene-3-ol, 3-hydroxybutyraldehyde, 3-methyl-n-butyraldehyde, 2,3-butanedione, 2-nonanone, and ethyl ester modified the overall flavor of the fermented milk (0.1≤OAV<1). According to the cluster heatmap, the flavor substances produced during fermentation and storage were significantly different. Similar results were also found by electronic nose detection. [Conclusion] The flavor compounds produced by the compound starter in milk during fermentation and storage endow fermented milk a good flavor.