ASSESSMENT OF THE MICROBIOLOGICAL QUALITY OF RAW EWES MILK BY RAPID COLORIMETRIC METHODS

Dye reduction (methylene blue and resazurin) was assayed on samples from bulk raw ewes milk used for cheesemaking taken on receipt at the dairy over one year at both 37 and 30-degrees-C. There were higher correlation coefficients between mesophilic aerobic counts and dye reduction with methylene blue (r = -0,77) and white end-point resazurin reduction (r = -0,79). These tests allowed also a good distribution of samples in hygienic categories. Resazurin tests (10 and 30 min) were also found suitable as a first grading test in order to classify unrefrigerated ewes milk by hygienic quality. Incubation at 30-degrees-C did not improve the relationship between dye reduction and mesophilic or psychrotrophic counts. The oxidase-positive count was checked as a rapid method of evaluating the potential psychrotrophic count in raw ewes milk. Prediction of the psychrotrophic flora (r = 0,64) was not accurate with this test. Traditional methods of husbandry and milk handling during production may have influenced the results.