Comparative Study of Rapid Test Strips and the National Standard Method to Analyse Staphylococcus aureus in Desalted Whey Powder

In this study, the results of counting test of S.aureus in desalted whey powder were compared by using the rapid test strips method and the national standard method, and the differences between the two methods were compared. Results showed that, after the test of desalted whey powder, it was confirmed that the Baird-Parker plate and the rapid test strips had no colony growth at 10⁻¹ dilution, and the results were both less than 10 CFU/g, indicating that the desalted whey powder used in this experiment had no effect on the additive quantity of standard strains. Besides, the results of compatibility test for standard strains showed that the desalted whey powder used in this study had no inhibition effect on the growth of standard strains. On that basis, 18 desalted whey powder samples with artificial contamination (added with quantitative standard strain of S. aureus) were counted and compared respectively by rapid test stripe method and national standard method. The repeatability obtained in the repeatability test was within the limit (r≤0.25). The results met the requirement of ISO 4833-1:2013 for repeatability. The t-test was used to analyze the results and it showed that there was no significant difference between those two methods. Therefore, rapid test strips method could be used to count S.aureus in desalted whey powder quickly, accurately and effectively.