Scientific journal

47 2008

Journal of Food and Nutrition Research
Summary No. 1 / 2008

Variability of growth parameters of Staphylococcus aureus in milk
Journal of Food and Nutrition Research, 47, 2008, No. 1, s. 18-22

Ľubomír Valík, Institute of Biochemistry, Nutrition and Health Protection, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, SK – 812 37 Bratislava, Slovakia. E-mail:

Summary: Growth of 15 strains of Staphylococcus aureus in milk at 15 °C was studied in 87 experiments, in order to determine the reproducibility of the growth parameters measured. The average growth rate (Gr) at 15 °C was 0.067 log CFU.h-1, ranging from 0.54 to 0.77 log CFU.h-1, which was equivalent to a doubling time ranging from 12.8 h to 9.0 h. Using a standard inoculation of an 18 h culture, the initial counts in milk of 3.68 log and the duration of the lag phase of 14.4 h were determined with the standard deviations of 0.2 log and 2.4 h, respectively. Based on ANOVA tests, the growth rates of individual strains did not produce different variances at the statistically significant 5% level. The results show that despite the errors connected with cultivation methods of determination microbial counts, the coefficient of variation (CV) of the growth rates for all 15 strains was as low as 7.1%. When 6 growth curves for a single strain were studied in two independent experiments, a CV of 1.2% for the growth rate was determined.

Keywords: growth parameters; variability; Staphylococcus aureus; predictive microbiology

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