The Inhibitory Effects of Varying Water Activity, pH, and Nisin Content on Staphylococcus Aureus Growth and Enterotoxin a Production in Whipping Cream

Abstract

AbstractTo determine the appropriate method to inhibit Staphylococcus aureus growth in whipping cream, enterotoxin A‐producing S. aureus strain was inoculated into whipping cream and stored at 36 ± 1°C for 36 h under varying water activity (Aw), pH, and nisin content. Duplicate samples were analyzed every 3 h to count the number of colonies by 3M Petrifilm™ Staph Express Count Plate, and the S. aureus enterotoxin A (SEA) was detected using ELISA kit (Tecra™). The modified Gompertz model was used to describe the S. aureus growth in whipping cream under various conditions. The results indicated that with the reduced Aw of whipping cream after adding sorbitol, S. aureus growth and SEA production was more effectively inhibited compared with other methods. Compared with the cream with pH 5.5 or containing 0.5 g/kg nisin, SEA production appeared later in the cream containing 7% sorbitol. The cream containing 14% and 21% sorbitol could markedly inhibit S. aureus growth and no SEA could be detected during 36 h. The results from this study may be beneficial for cream manufacturers to improve the safety of their products.Practical ApplicationsThe purpose of this study is to find an appropriate method to inhibit Staphylococcus aureus growth and SE production whenever the whipping cream is contaminated with S. aureus during whipping, piping, and storage. The result showed that the water activity of the cream reduced by adding sorbitol had better effect against the S. aureus growth and SE production. The application of the result may be beneficial for manufacturers to formulate whipping cream that limit the ability of S. aureus to produce SE, thereby reducing the risk of staphylococcal food poisoning.