Determination of the end of shelf-life for milk using Weibull hazard method

The shelf life of pasteurized milk is traditionally estimated by the counts of both total and psychotrophic microbial load. This study examins the rel ationship between the total and psychotrophic microbial growth in milk and its sensory shelf life as measured using the Weibull hazard method. Milk wa s stored at five constant temperatures (2, 5, 7, 12 and 15 degreesC) and bo th total and psychotrophic microbial counts were used to obtain the lag tim e and the growth rate values. The lag time of the total and psychotrophic g rowth responded to temperature following the Arrhenius equation. The loss o f sensory quality of the milk followed a log shelf life vs. temperature dep endency. It was found that there was no correlation between the microbial c ount at the end of shelf life and the sensory quality of the milk. It is th erefore suggested that microbial counts should not be used to determine the sensory shelf life of milk. The Weibull method gave end of shelf life valu es fairly similar to that of prior work using the American Dairy Science As sociation scoring methods.