Heat resistance of salmonellae in concentrated milk.
The heat resistance of Escherichia coli, Salmonella typhimurium, and Salmonella alachua in milk solutions containing 10, 30, 42, and 51% (w/w) skim milk for total solids was determined. Increased milk-solids level effected a significant increase in the heat resistance of each organism. Although E. coli was more heat-resistant than both strains of Salmonella in 10% milk, the situation was reversed in 42 and 51% milk. Prior growth temperature was found to exert a profound effect on the heat resistance of S. typhimurium. Growth of S. typhimurium in 42% milk solids for 24 hr did not greatly enhance the thermal resistance of the organism when heated in a fresh 42% solids concentrate. Application of a partial vaccum during heating greatly diminished the decimal reduction times of S. typhimurium and E. coli and, in addition, virtually eliminated the protective effect of increased solids level.
D000818:Animals; D001274:Atmospheric Pressure; D001431:Bacteriological Techniques; D002452:Cell Count; D002470:Cell Survival; D004926:Escherichia coli / Q000254:growth & development / Q000302:isolation & purification; D005516:Food Microbiology; D005519:Food Preservation; D006358:Hot Temperature; D008892:Milk; D012475:Salmonella / Q000254:growth & development* / Q000302:isolation & purification; D012486:Salmonella typhimurium / Q000254:growth & development / Q000302:isolation & purification