Studying the Population Dynamics of NSLAB and Their Influence on Spores During Cheese Ripening

Abstract

Cheese ripening involves microbial changes, with starter lactic acid bacteria (SLAB) initiating fermentation and nonstarter lactic acid bacteria (NSLAB) driving flavor and texture development. However, heat-resistant spores of Clostridium and Bacillus can survive pasteurization and cause spoilage during ripening. This study evaluated NSLAB dynamics in the presence of spores during cheese ripening. Cheddar cheese samples at pilot-scale level (110 L) with four treatments, namely control, with spores of B. licheniformis (T1), with spores of Cl. tyrobutyricum (T2), and both spores (T3) at 2.0 Log10 CFU/mL, were ripened at 7 °C for six months. SLAB declined from 8.0 to 0.2 Log10 CFU/g, while NSLAB increased from 2.0 to 8.5 Log10 CFU/g by month three and maintained their counts up to six months, unaffected by spore presence. Spore counts were ≤1.45 Log10 CFU/g in controls but reached 2.94 ± 0.02 (T2) and 2.48 ± 0.03 (T3), correlating with spoilage signs after five months. MALDI-TOF identified L. rhamnosus (up to 37%) and L. paracasei (up to 25%) as dominant NSLAB across treatments. Physicochemical parameters were not significantly affected by higher spore levels. While NSLAB dominated, they were inadequate to prevent spoilage in spore-inoculated samples exceeding 2.0 logs during cheese ripening.