Antifungal Activity of Sourdough Microbial Consortia and the Impact of Volatile Organic Compounds

Bread is a global dietary staple, but its susceptibility to fungal spoilage causes substantial food waste, economic losses, and greenhouse gas emissions. Volatile organic compounds (VOCs) produced by sourdough microorganisms can contribute to the prevention of bread spoilage; however, the specific VOCs that exert the protective effect in the bread matrix have not been precisely identified. Our study investigated the antifungal activity of sourdough lactic acid bacteria (LAB) consortia, both alone and in combination with yeast and acetic acid bacteria (AAB), as well as the VOC profiles of sourdough and sourdough bread. The consortium comprising Lactiplantibacillus plantarum 9-5 and Levilactobacillus brevis 9-2 (LAB), Monosporozyma unispora R3SD1d (yeast), and Acetobacter fabarum WB and Komagataeibacter rhaeticus Ch2 (AAB) extended the mold-free shelf life of sourdough bread by 8–20 days after challenge tests. VOC analysis revealed that sourdough bread had significantly higher concentrations of ethyl esters of hexanoic and octanoic acids with 6.3- to 9.7-fold increase in peak areas after three days of refrigerated storage, assuming their decisive role in prevention of fungal spoilage. In conclusion, the use of this consortium is promising to significantly extend bread shelf life, but also to enrich the bread VOC profile.