[Study of total count, E. coli and coliforms contamination of raw milk from letdown stage till delivery to factory in Lorestan province]

ABSTRACT

The primary quality of raw milk is affected by several factors including animal nutrition, animal health, milk components, and its bacterial activity and these factors are effective on the final products. Therefore, the quality of raw milk depends on time and milk condition from production to delivery. In Lorestan, 97% of the milk production is obtained from rural and small units. This study was carried out to determine the factors affecting the bacteriological quality of raw milk from letdown phase till delivery to factory and to find out the critical points of bacterial contamination in the years 2003 and 2004. In this study, the collecting centers of raw milk with a capacity of more than 3 tons, between 1.5 to 3 tons, and fewer than 1.5 tons were included as the centers with high, moderate, and low capacity respectively. The sampling stages consisted of cow milk letdown, milk collecting equipment, milk collecting tankers, milk cooling tanks, and milk delivery to factory. Microbial experiments consisted of standard plate count [SPC], E. coli, and coliforms. All the collected samples were 45 ones in each month and 540 samples in a year. Being converted to Log 10, the data were analyzed by the SPSS software [version 11.5] and GLM procedure was used to determine the effects of month, capacity of centers, and sampling stages. Based on the results of the study, the average total count [TC] in all seasons in Lorestan province was 6.43 o 0.37 cfu/m. The effects of month, capacity of centers, and the sampling stages on TC, E. coli, and coliforms were statistically significant [p<0.01]. Additionally, the lowest TC [6.31 o 0.38 cfu/m] was in January while the highest [6.57 o 0.31 cfu/m] was in August. Moreover, the decreasing trend of TC started from September and was the lowest in January and February. Correlation coefficients showed that there was a significant positive correlation between TC and E. coli [r=0.79] and TC and coliforms [r=0.90, p<0.01]. The major problems of milk collecting in Lorestan province are the long distances of some milk collecting centers from the milk factories as well as the long milk delivery time which play important roles in increasing TC from letdown stage till delivery to factory in addition to the insufficient road facilities in some of the villages in Lorestan province