Development of a Natural Coating Based on Fermented Milk Whey for Biopreservation of Cheese

Consumer demand for natural, additive-free foods is increasing. Following the trend, this study evaluated the antifungal potential of lactic acid bacteria (LAB) against <i>Penicillium</i> species commonly found in cheese, using both LAB ferments and hydroxypropylmethylcellulose (HPMC) coatings. LAB strains were first screened with a dual-culture assay. Fermentations in Man-Rogosa-Sharpe (MRS) broth and milk whey were lyophilized and tested, with whey-based ferments showing greater antifungal activity. All whey ferments inhibited fungal growth, with KK₁₃, KB₂, KB₃, and KB₄ being the most effective based on MIC and MFC assays. KB₃-fermented whey had the highest levels of antifungal metabolites, such as phenyllactic acid. A coating containing 5% HPMC and 100 g/L of KB₃-fermented whey was applied to cheese slices, reducing the fungal counts of <i>Penicillium commune</i> by more than 1 Log₁₀ CFU per gram and extending shelf life by 12 days. In whole-cheese trials with natural contamination, this coating delayed visible fungal growth until day 60, extending shelf life by 45 days compared with uncoated samples and 33 days compared with coated controls. These findings support the use of LAB-fermented whey and HPMC coatings as natural preservation strategies, thereby contributing to the sustainable reuse of dairy by-products.