Fate of Staphylococcus aureus in Whipped Butter

This study determined growth and survival of Staphylococcus aureus strains 100-A, 196-E, 254, 473, 505, and 521 in whipped butter made by whipping butter produced from inoculated cream or in whipped butter inoculated after manufacture. Cream was inoculated to contain ca. 10⁴ to 10⁵ S. aureus /ml and then was held at 4°C for 3 d, at 22°C for 36 h, or at 37°C for 24 h. After incubation, cream was churned to obtain butter which then was either lightly salted (1.0%, w/w) or left unsalted. Fresh sweet cream also was churned to obtain sweet cream butter which was lightly salted or left unsalted. Sweet cream butter was inoculated to contain ca. 10⁵ S. aureus /g. Butter containing S. aureus was brought to 15°C and whipped for 5-7 min with a three-speed hand mixer. Whipped butter was held at 4, 10, 15, and 25°C for up to 6 weeks. Whipping of butter influenced growth and survival of all strains of S. aureus . Whipped butter inoculated after churning and before whipping was a better medium for growth of the pathogen than was whipped butter made from butter that had been churned from inoculated cream. Whipping of butter had a greater effect than salt on the ability of S. aureus to grow or survive. Variability among strains also was important in determining growth and survival of S. aureus in whipped butter.