Milk contamination in different points of the process: I) Aerobic mesophilics and psychrotrophics microorganisms

Abstract

To improve the microbiology quality of the milk produced in Brazil, steps like the refrigeration have been implanted in the dairy sector but, temperatures of 4oC are selective for psycrotrophics microorganisms. These microorganisms, irrespective of their optimum growth temperature, are able to multiply in refrigeration temperature and produce heat-resistant extra celular enzymes that can cause changes, especially in dairy products and UHT milk. This work has the objective to determine the main points of milk contamination in dairy process and the effect of refrigeration on the control and multiplication of microorganisms. Five properties located in Londrina city- PR were aviated. Different points have been assessed in the dairy process and mesophilics (35oC/48hs) and psychrotrophics (21oC/25hs) microorganisms were researched. The main contamination points found were the milk cans, bulk milk tanks, residual water in the dairy equipments and teats bad cleaned. The residual water on the bulk milk tanks, on the cans, teats bad cleaned and the dairy centrifuge equipment were the main source of psychrotrophics. The quantity of psycrotrophics in all points assessed were greater than the ideal limit (10% of the mesophilic count). In the refrigerated milk, the psychrotrophics count over came the mesophilics count, showing that the mesophilics count can under estimate the real microflora of refrigerated milk, what means that psychrotrophics are the best indicators for refrigerated milk contamination. By what means, refrigeration at 4oC is not sufficient to control the multiplication of the psycrotrophics group, is necessary to associate good practices to avoid or control the milk contamination by psycrotrophics in the main contamination points detected in this study.