A study in Ecuador of the calibration curve for total bacterial count by flow cytometry of raw bovine milk

Abstract

The total bacteria count (TBC) analysis, as a parameter of hygienic quality in raw milk, is one of the most requested analysis by dairy industries and food safety organizations. This analysis is done by the reference method of plate count expressed as colony-forming unit per milliliter (CFU/mL). However, the alternative method by flow cytometry currently is a reliable and faster method than the reference method of Individual Bacteria Count per milliliter (IBC/mL). The aim of the study was to determine the linear regression equation and correlation between the reference method and the alternative method by flow cytometry. Because the activities of livestock management during milking are different in each country, a total of 357 milk samples with a range from 100000 to 1;5 millions of UFC/mL from two altitudinal floors: Z1 (> 3000 masl) and Z2 (1050 masl) were done in Ecuador. Both methods were analyzed at the same time, (maximum deviation of ± 1 h), following the recommendations of the IDF=ISO-196 and the AOAC 986.33 standard. The results showed a high correlation between the two methods (r = 0;91) and since there were no statistic differences for the effect of Zones 1 and 2, it was not considered, suggesting the use of a unique linear regression equation.