The Effect of Seasonal Variation on the Chemical and Microbial Quality of Raw Milk Samples Used in Qazvin, Iran

Abstract

Although milk and dairy products are considered as nutritious food for human, it serves as a beneficent medium for the growth of many microorganisms such as psychrotrophic microorganisms (PMs). PMs can be affected by the milk quality and dairy products by production thermostable enzymes. The present study aimed to evaluated the psychrotrophic microorganisms count (PMsC) of raw cow milk samples in milk collection centers. A total of 60 raw cow milk samples were collected from 15 main milk collection centers located in Qazvin, Iran for a period of one year (four seasons). The mean±SD of PMs, Ph, and acidity levels for a period of one year was 4.83±0.43 Log₁₀ CFU/ml, 6.30±0.41, and 20.13±3.21°D, respectively. PMsC, Ph, and acidity levels in cold seasons (autumn and winter) were greater than warm seasons (spring and summer). It may be expected that PMs values can affect the pH and acidity levels while no significant relationship (P>0.05) was found among PMs, Ph, and acidity levels. Seasonal variations had a significant effect (P<0.05) on PMs values while seasonal variations had no significant effect (P>0.05) on the pH and acidity levels. 55% (33 out of 60) of milk samples were in the accepted limit. Milk quality properties in Qazvin in terms of PMs were relatively within the hygienic standards limit.