The Growth of Staphylococci in Condensed Skimmilk

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Abstract
Preheat treatment of skim milk at 165[degree] or 185[degree] F for 30 minutes before condensing did not affect the growth of 2 cultures of Staphylococcus aureus in condensed skim milk. Growth of one of these cultures was retarded somewhat when the preheat treatment was 150[degree]F for 30 minutes; growth of the other culture was not retarded. Cultures of staphylococci grew optimally or nearly so at temperatures ranging from 90[degree] to 113[degree]F in condensed skim milks having solids concentrations ranging from approximately 30 to 50%. Three of 6 cultures grew, although slowly, in 40% milk solids at 116[degree]F and one grew under similar conditions at 118[degree]F. Under conditions of simulated vacuum condensing, growth was less extensive than under normal atmospheric pressure. However, growth was sufficiently rapid to exclude the possibility that subatmospheric pressures, likely to prevail in a vacuum condensing operation, would afford sufficient retardation of growth to be of any practical significance in controlling growth of staphylococci.