Characterization and Comparative Analysis of the Key Aroma Compounds in Selected Kefir and Yogurt Samples by Sensomics

Aroma is a key attribute influencing the quality of fermented dairy products. Volatile and odor-active compounds of kefir (SN) and three yogurt samples (S1, S2, and S3) were analyzed using the Sensomics approach. Sensory results showed that kefir scored lower than yogurt in sweet, milky, and fermented odor attributes. Gas chromatography-time-of-flight mass spectrometry (GC-ToF/MS) detected 61 volatiles, and gas chromatography-olfactometry (GC-O) further identified 16 odor-active compounds, including three unknown compounds with notable sensory relevance. Based on odor activity value (OAV) calculations, aroma recombination, and omission tests, 2,3-butanedione, hexanal, acetoin, and butanoic acid were identified as key aroma compounds in the kefir sample (SN), contributing to buttery, grassy, creamy, and cheesy aromas. In the yogurt sample (S1), the key contributors were 2,3-butanedione, acetoin, and butanoic acid, imparting buttery, creamy, and cheesy attributes. These findings enhance the understanding of aroma profiles in fermented milks and support future product optimization.