Effect of Staphylococcus aureus Contamination on the Microbial Diversity and Metabolites in Wholewheat Sourdough

Whole wheat sourdough products are becoming increasingly more popular, and Staphylococcus aureus is a common opportunistic pathogen in dough products. The effects of S. aureus contamination (10(2) cfu/g) on metabolites as well as titratable acidity (TTA), pH, and microbial diversity of sourdough were investigated. S. aureus contamination significantly decreased the content of mannose while increasing the sorbitol in sourdough (p < 0.05). The S. aureus contamination significantly reduced the number of lactic acid bacteria (LAB), such as Lactobacillus curvatus, and the TTA values (p < 0.05). Furthermore, S. aureus contamination significantly reduced the content of most esters and acid flavor compounds while significantly increasing the content of 2,4-decadienal (p < 0.05), which is a compound that could have a negative impact on the flavor of sourdough. The PCA model developed based on volatile metabolites data could be used to distinguish contamination of S. aureus in sourdough cultured for 4 h. Sorbitol, 2,3-dimethylundecane, 1-pentanol, and 3-methylbutanoic acid were newly found to be the characteristic metabolites in S. aureus-contaminated sourdough.

Automated summary

S. aureus contamination in sourdough has significant effects on metabolites, titratable acidity, and microbial diversity. It decreases the content of mannose, increases the content of sorbitol, reduces the number of lactic acid bacteria, decreases the acidity values, reduces the content of esters and acid flavor compounds, and increases the content of 2,4-decadienal. A PCA model using volatile metabolites data can be used to detect S. aureus contamination in sourdough.