en تخصصي Special Original article Original article <p style="text-align: justify;"><span style="font-family:times new roman;"><strong>Background</strong>: 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.<br> <strong>Methods</strong>: </span><span style="font-family:times new roman;">Hundred</span><span style="font-family:times new roman;"> 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 <em>Escherichia coli</em> counts were carried out at </span><span style="font-family:times new roman;">expiration</span><span style="font-family:times new roman;"> date of the samples according to the standard procedures. Data were statistically analyzed using SPSS software (version 16.0, SPSS Inc., Chicago, IL, USA).<br> <strong>Results</strong>: The mean value of pH, acidity, and </span><span style="font-family:times new roman;">sensory</span><span style="font-family:times new roman;"> 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 <em>E. coli</em> counts of the samples were 4.11, 0.77, and 0.01 log10 colony forming unit/ml, respectively. No significant relationship (<em>p</em>>0.05) was found between various studied parameters and different milk brands.<br> <strong>Conclusion</strong>: Storage of milk pouches out of </span><span style="font-family:times new roman;">refrigerator</span><span style="font-family:times new roman;"> 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.</span></p> Milk, Food Quality, Food Preservation, Food Safety 53 57 http://jfqhc.ssu.ac.ir/browse.php?a_code=A-10-224-4&slc_lang=en&sid=1 M. M. Azizkhani m.azizkhani@ausmt.ac.ir Yes Faculty of Veterinary Medicine, Amol University of Special Modern Technologies, Amol, Iran F. Tooryan No Faculty of Veterinary Medicine, Amol University of Special Modern Technologies, Amol, Iran