Keeping Quality of Pasteurized Milk for Retail Sale Related to Code Date, Storage Temperature, and Microbial Counts

Keeping quality of milk samples collected in original containers from fillers and stored at 1.7, 5.6, and 10.0 C remained organoleptically acceptable, on the average, 17.5, 12.1, and 6.9 days, respectively. Samples were tested for specific groups of bacteria at collection and when the milk became unacceptable (flavor score < 36). In addition to a total aerobic count the specific groups included pseudomonads, lipolytic, proteolytic, acid-producing, and coliform bacteria, and lipolytic and proteolytic pseudomonads. Keeping quality at any storage temperature was unrelated to the manufacturer's code date (last day product is to be sold). There was a significant correlation between keeping quality at 10.0-C storage and the other two storage temperatures, suggesting a practical test to measure keeping quality at the lower temperatures. Microbial counts, made at bottling and when the sample became unacceptable, were not consistently related to the time required for milk to become unacceptable at any storage temperature. When samples were stratified by flavor defect, certain microbial tests were significantly related to keeping quality.