ENUMERATION AND PREVENTION OF MICROBIAL CONTAMINATION OF PASTEURIZED MILK DURING THE MANUFACTURING PROCESS

Abstract

Milk is a source of high nutrient content fortified with essential ingredients for a healthy growth and is thus a perfect medium for microorganisms to grow, resulting in subsequent spoilage. A frequently employed method of retarding spoilage of milk is pasteurization. This destroys all pathogenic organisms and guarantees a shelf life of 3 days. Pasteurized milk, to be up to Sri Lanka Standards, should be completely devoid of coliforms and should not contain more than 30,000 microbial colonies per ml. But these standards are not always met due to the cross contamination through equipment and people. Therefore a study was done to evaluate the effectiveness of oxonia as a sanitizer and hence to eliminate microbial contamination. Degree of contamination was determined by drawing samples from all stages after pasteurization and carrying out Total Plate Count and coliform tests. Effectiveness of oxonia was evaluated by enumerating microbial counts before and after its application as a sanitizer. Workers, their hygienic practices and traffic flow within the factory was observed and examined thoroughly to identify causes of cross contamination. Results indicated that the sources of re-infection were parts of the plant in which Clean In Place (CIP) was not sufficient to provide complete sanitation. Analysis of the test results proved oxonia to be a very good sanitizer that can be used on a permanent basis. ' Suggestions such as HACCP (Hazard Analysis and Critical Control Points) implementation and improving worker hygiene were made to further reduce the microbial count of pasteurized milk.