Abstract:During fermentation, benzene and benzene derivatives can be produced in yogurt, but there is a lack of studies on the pattern of production and the amount produced. In this study, single-strain fermentation and mixed-strain fermentation using Lactobacillus bulgaricus and Streptococcus thermophilus were compared, and the pattern of production of benzene compounds and their contents in yogurt were studied. The results showed that the amount of benzene compounds produced in the single-strain fermentation with Streptococcus thermophilus was higher than that produced in the single-strain fermentation with Lactobacillus bulgaricus; the peak production of benzene compounds occurred after about 24 h of ripening, and acetophenone showed the highest content (Streptococcus thermophilus: 2.64±0.34 μg/L; Lactobacillus bulgaricus: 1.95±0.22 μg/L) among all the benzene compounds. When mixed-strain fermentation was performed with both strains, the contents of benzene and benzene derivatives in yogurt were higher than those of the single-strain fermentations. The results of mixed-strain fermentations with different ratios of the two strains were compared. The relatively lowcontents of benzene and benzene derivatives in yogurt were presented with a 1:1 ratio of Lactobacillus bulgaricus and Streptococcus thermophilus, and the content of methylbenzene was the highest amongst produced benzene compounds at 3.68±0.15 μg/L. According to the requirements for drinking water, the contents of benzene and benzene derivatives in yogurt for both single-strain and mixed-strain fermentation were lower than the maximum levels allowed for drinking water; hence, the benzene and benzene derivatives in yogurt, in theory, will not have an impact on human health.
