Potential for Presence and Growth of Staphylococcus aureus in Brazilian Minas Cheese Whey

Presently there is a great interest in further utilization of Minas cheese whey by the Brazilian food industries. The potential growth of Staphylococcus aureus in Minas cheese whey was evaluated. S. aureus strain 100 was inoculated at levels of (log₁₀) 3 and 5 cells/ml in sterile whey along with (log₁₀) 7.17 cells/ml of Streptococcus lactis and Leuconostoc cremoris starter and incubated at 37 C for 8 h. S. aureus growth occurred at both levels of inoculum. Better growth was observed at the higher inoculum (P < 0.05). Thermonuclease was detected after 2 h of incubation only in the whey inoculated with (log₁₀) 5 cells/ml and when growth reached about (log₁₀) 7. Then we determined the presence of S. aureus in Minas cheese whey after inoculation of pasteurized milk with strains 100, 137 and 243 alone and in combination at levels (log₁₀) of 4.23 to (log₁₀) 6.20 with or without starter, and sampling the whey 60 and 70 min after the cheese processing started. A significant sampling time effect for S. aureus counts was observed (P < 0.01). Duncan's Multiple Range test showed that there were significant differences in strain behavior. Starter culture effect and the interactions were not significant (P > 0.05). The failure to observe a starter culture effect upon staphylococcal counts in whey may be due to the short time between starting the cheesemaking process and sampling of whey, insufficient amount of lactic acid produced by the starter culture and the detrimental effect of the processing temperature (34-36 C) upon the starter bacteria.