Identification of odor compounds and odor-active compounds of yogurt using DHS, SPME, SAFE, and SBSE/GC-O-MS

Yogurt is widely acknowledged as a healthy dairy product with unique aroma. However, the changes in the odor compounds often affect the storage and shelf life of yogurt. Besides, the complex colloidal system and low concentration levels of most of odorants make it more difficult to be analyzed. Therefore, this study extracted the odor compounds of yogurt through four extraction methods, including dynamic headspace sampling (DHS), solid phase micro-extraction (SPME), solvent-assisted flavor evaporation (SAFE), and Stir bar sorptive extraction (SBSE). A total of 117 odorants, including 27 esters, 27 alcohols, 22 ketones, 16 acids, 15 aldehydes, 5 sulfides, and 5 other compounds, were identified. Of which, 31 odor-active compounds were perceived, and 12 compounds were smelled for the first time in yogurt. Of the four methods, DHS showed the most outstanding extraction effect by obtaining 88 odor compounds. Around 13 volatiles were characterized as the key odor-active compounds of yogurt. Similarly, acetophenone and butyl acrylate were detected as the key odor-active compounds of yogurt for the first time. 2,3-Butanedione was the vital odor-active compound with the highest flavor dilution (FD) factor in yogurt. The results concluded that the odor-active compounds in yogurt might have synergistic and masking effects between them.