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Growth and enterotoxin production by Staphylococcus aureus during manufacture and storage of telita type cheese

Abstract:

Telita is an artisan, white, cooked paste fresh cheese produced in Venezuela. Commonly, it is made from unpasteurized milk following a not standardized procedure and marketed at room temperature, there for presence and growth of pathogens is a potential risk. The goal of this study is was to establish Staphylococcus aureus grown rate and enterotoxins production during telita cheese making and storage. Cheese samples are made using contaminated milk containing two different doses, 103 and 105 CFU/mL of a strain enterotoxigenic of S. aureus, following a traditional procedure and stored for 6 days at two different temperatures, 25 and 12°C. The population of S. aureus is determined during manufacture (acidification, curding, salting and cooking) and storage at days (d) 2, 4, and 6. Additionally, the presence of enterotoxins A and B is measured by reverse passive agglutination immunoassay (SET RPLA). During telita type cheese manufacture, the population of S. aureus decreased (P· 0.05) while cooking at 70°C/10min. In storage, microorganism population is controlled by refrigeration, reducing the number of viable cells in one log cycle after day 2. However, at room temperature an increase (P· 0.05) of the microorganism population is observed, reaching final values of 107 and 106 CFU/g, after to 2 and 4 d storage, respectively, from samples with initial population level of 105 and 103 CFU/g, respectively. Enterotoxins A and B were detected only in 107 CFU/g samples stored at 25°C. This study shows that cooking temperature/time and refrigerated temperature throughout storage, significantly influenced (P· 0.05) growth and survival of S. aureus. These findings allows preventive recommendations for artesian cheese-makers to help improve product safety, use a cooking time relationship of 70°C/10min and a store temperature of 12°C.