低温殺菌白カビチーズ中の黄色ブドウ球菌の生存率：異なる保存条件と塩水濃度下での保存

Contamination of brined white cheese (BWC) with pathogenic bacteria is a major concern in the Mediterranean region. This study aimed to investigate the survival capability of Staphylococcus aureus in white cheese immersed into different brine solutions (0.0%, 2.5%, 5.0%, 7.5%, and 10.0%) under different temperatures. A cocktail of three strains of S. aureus, were inoculated at ca. 5 log₁₀ CFU/g in BWC. The cheese was stored for 30 days at 4°C, 10°C, or 24°C. The water activity and salt content in cheese ranged between 0.99% and 0.0% in un-brined cheese to 0.96% and 5.2% in the BWC immersed in 10.0% NaCl. The initial pH of cheese was ca. 6.6 and it dropped significantly (p < 0.05) after 30 days, especially under high storage temperature. S. aureus was able to survive in BWC at 4°C throughout the storage period at counts higher than 3.8 log CFU/g. While at 10°C, the counts remained higher than 6.0 log CFU/g. In comparison, at 24°C, S. aureus reached to ca. 9.5 log CFU/g after 15 days of storage. TMC (total mesophilic bacterial count) and yeast and mold counts were significantly (p < 0.05) lower at higher brine concentrations (7.5% and 10.0%) and lower temperature (4°C). However, the TMC and yeast and mold counts reached their maximum levels after 10 and 5 days when BWC was stored at 10°C and 24°C, respectively. S. aureus can survive well in BWC preserved in various brines and different storage temperatures. However, the counts were particularly lower when BWC was kept refrigerated and immersed into 10% brine, emphasizing the necessity of keeping BWC refrigerated and necessitating exploring appropriate preventive measures to reduce the potential risk associated with this pathogen.