Lactiplantibacillus plantarum as an adjunct culture exhibits antifungal activity in shredded Cheddar cheese

Fungal spoilage is a substantial concern for the dairy industry, due to mycotoxin formation and a cause of food waste. In this study, several strains of Lactiplantibacillus plantarum from different sources were investigated for their antifungal activity and performance as adjunct cultures in Cheddar cheese production. All strains grew well in milk with minimal acidification. Although high concentrations of NaCl affected their growth in agar-based media, the salt concentration did not influence their antifungal activity towards the major spoilage mould Penicillium commune. L. plantarum strains were able to be inoculated in milk simultaneously as cheese starter cultures, without obstructing acid production. When added at the start of Cheddar cheese production as adjunct cultures, all strains of L. plantarum significantly prolonged the shelf life of shredded cheese. Visual spoilage of shredded cheese with deliberately inoculated P. commune was delayed a further 2-3 days when L. plantarum was included as an adjunct culture, compared to cheese without L. plantarum addition. Environmental fungal spoilage of shredded cheese was delayed by more than 20 days when L. plantarum was included as an adjunct culture in Cheddar cheese production, compared to cheese without L. plantarum addition. The results of this study show that L. plantarum has potential as a biopreservative adjunct culture in Cheddar cheese.