Fate of Staphylococcus aureus in Whey, Whey Cream, and Whey Cream Butter

Abstract

Fresh Cheddar cheese whey was inoculated with ca. 106Staphylococcus aureus/ml and held at 4, 25, and 37°C for 48h. Numbers of staphylococci decreased in whey at 25 and 37°C and decreased or remained constant in whey at 4°C. When Cheddar cheese whey was neutralized with sodium hydroxide before inoculation with ca. 102 or 106S. aureus/ml, numbers of the bacterium increased at all incubation temperatures. Viability of S. aureus strains in whey butter made from inoculated whey cream (from Cheddar cheese whey) was determined. Whey cream was either neutralized to a titratable acidity of .15% or untreated before inoculation with ca. 104S. aureus/ml. Butter churned from the whey cream was held at 4, 25, and 30°C for up to 4 wk. Viability of S. aureus was enhanced in lightly salted (1%) whey cream butter and in butter made from neutralized whey cream. Strains of S. aureus did not survive in unsalted or in salted (1.5%) butter made from untreated whey cream.