Investigating the effect of addition of probiotic microorganisms (bacteria or yeast) to yoghurt on the viability and volatile aromatic profiles

Aroma compounds are key components of food, and the food industry places a high priority on the enhancement of these chemicals. Streptococcus thermophilus (ST), Lactobacillus bulgaricus (LB), Limosilactobacillus reuteri (LR), Lactobacillus acidophilus (LA-5), Bifidobacterium bifidum (BB-12) and Saccharomyces boulardii (SB) were mixed starter cultures used in this study to improve the flavor of the yoghurt. To make the yoghurt, four starter mixtures were used, with the presence of the common yoghurt starter (CYS) as a control sample: CYS + LR, CYS + LA-5, CYS + BB-12, and CYS + SB. The pH, total acidity, and starter culture viability of yoghurt samples were then estimated over the course of 21 days of storage, while aroma compounds and sensory evaluation were determined on the first day of storage. The pH and total acidity of the yoghurt samples ranged between 4.2 and 4.5 and 0.84–0.93% on the first day to storage respectively, according to the results. The vaiable count of probioticbacteria were 8.1 (LR), 9.3 (LA-5), and 7.9 (BB-12) log CFU/g while it was 6.9 CFU/g for the probiotic yeast at the end of storage period. Furthermore, yoghurt samples contained a total of 47 volatile compounds. Esters and alcohols had the greatest impact on the formation of volatile compounds in fermentations containing various probiotic microorganisms and yoghurt starter. The mixture of aroma compounds produced therefore in the current study would be useful for selecting starter cultures that could serve as significant resources in the development of novel fermented milks.