Chemical and Microbial Quality of Iranian Commercial Pasteurized Milk Samples at Their Expiration Date

Background: Milk can provide a good medium for growth and proliferation of various spoilage and pathogenic microorganisms. The main aim of this study was to evaluate the chemical and microbial quality of Iranian commercial pasteurized milk samples at their expiration date. Methods: Hundred samples of pasteurized milk packaged in polyethylene pouches were randomly collected from local markets of Amol, North of Iran. Acidity, pH, total viable, coliforms and Escherichia coli counts were carried out at expiration date of the samples according to the standard procedures. Data were statistically analyzed using SPSS software (version 16.0, SPSS Inc., Chicago, IL, USA). Results: The mean value of pH, acidity, and sensory score of the samples were obtained as 6.6, 0.15 g lactic acid/100 ml, and 6.4, respectively. Also, the mean value of total viable count, coliforms and E. coli counts of the samples were 4.11, 0.77, and 0.01 log10 colony forming unit/ml, respectively. No significant relationship (p>0.05) was found between various studied parameters and different milk brands. Conclusion: Storage of milk pouches out of refrigerator in supermarkets of Iran must be strictly avoided in order to improve chemical and quality of this product. Also, proper pasteurization process and reduction of post-pasteurization contamination are the other keys to produce high-quality pasteurized milk.