Correlation between Methylene Blue Reduction Test and Standard Plate Count of Raw and Pasteurized Milk

Abstract

Milk is highly nutritive food containing all essential nutrient necessary for growth and development of children and adults. Milk is sterile at secretion, but it gets contaminated during milking, processing and storage with pathogenic bacteria which is of public health significance. Milk borne infection is an important constituent of food borne disease globally and responsible for approximately 4% of the food borne infection worldwide. The objective of study was to evaluation of the initial bacterial load of milk to determine whether to accept or reject the milk at farm level. A total of 100 milk samples (50 raw and 50 pasteurized milk) were collected from Ranchi, Jharkhand. Bacteriological analysis of milk was evaluated by Methylene Blue Reduction Test (MBRT) and Standard Plate Count (SPC). The MBRT result revealed that 10%, 40%, 42% and 08% of raw milk were of very good, good, fair and poor quality, respectively. While 16%, 52% and 32% of pasteurized milk were of very good, good and fair quality, respectively. SPC of raw milk ranged from 3.54 to 6.74 log10CFU/ml and 82% were of very good quality, 14% were of good quality, 02% were of fair quality and 02% poor quality. The pasteurized milk was found to be within the acceptable limit. A correlation coefficient (r) was 0.875 (P<0.01) it showed a strong positive relationship between MBRT and SPC indicating that the microbial quality of raw milk can be assessed by MBRT. MBRT can be performed as it effective, economical, takes less time and not laborious as compared to other expensive and time taking microbiological methods.