Effect of prebiotics on rheological properties and flavor characteristics of Streptococcus thermophilus fermented milk

The fermentation characteristics and aroma production properties of lactic acid bacteria can influence the flavor quality of fermented milk, which is one of the important factors influencing the consumer preference. In this study, fermented milk was prepared using Streptococcus thermophilus, and dynamic changes in its quality, including rheological properties and flavor characteristics, were evaluated throughout the fermentation process. The results showed that benzaldehyde, 2-undecanone, octanoic acid, n-hexanol and 2-nonanol were the key flavor components during the fermentation process. The quality of the fermented milk tends to be stabilized after 24-h, showing the minimal off-flavor and optimal fermented aroma at 48-h. Three prebiotics (inulin, Galactooligosaccharides and inulin mixed with Galactooligosaccharides) were added to Streptococcus thermophilus fermented milk separately, and the results showed that inulin was the most effective group in improving the organoleptic quality of the fermented milk. These findings contribute to our understanding of the release and retention of flavor compounds during fermentation and can be used as a scientific reference for the application of probiotics and flavor-producing lactic acid bacteria in fermented milk processing.