ABSTRACT
Whole, lowfat, and nonfat fluid milk samples were collected from dairy plants on the day of bottling and each set of the three types of milk was processed from the same raw milk supply. Bacterial analyses for total aerobic count and for specific degradative types were made immediately after collection. Samples were also stored at 1.7, 5.6 and 10.0 C to test for flavor deterioration. Total count of aerobic bacteria and of specific degradative types did not differ significantly among the three types of milk. Organoleptic analysis was made periodically to determine milk quality (flavor score) and defect (flavor). At any of the storage temperatures the keeping quality (days required from bottling to reach a flavor score of < 36) was unrelated to the length of time between bottling and last day of sale (code date) assigned by the processor. At 5.6- and 10.0-C storage, more whole milk samples were criticized for more serious flavor defects (e.g. putrid) than for the less serious ones (e.g. lacking freshness) found in the lower fat milks. Keeping quality of all three types of milks at 1.7- and 5.6-C storage could be predicted from keeping quality determined at 10.0 C with equations previously developed for whole milk.
ABSTRACT
Raw milk samples were examined for number and percentage of bacteria resistant to seven antibiotics: penicillin, ampicillin, chloramphenicol, neomycin sulfate, polymyxin B sulfate, tetracycline and streptomycin sulfate. A significant negative correlation was found between the total aerobic count of the milk sample and the concentration (above 5 or 10% of the total count) of bacteria in each milk resistant to each of the antibiotics tested. Three of 42 gram-negative isolates were capable of transferring their antibiotic resistance to Escherichia coli . Substantial numbers of antibiotic-resistant bacteria in raw milk were found and some survived pasteurization. Inspection of farms failed to indicate a relationship between farm practices or use of antibiotics in feed or as pharmaceuticals and number of antibiotic-resistant bacteria in the raw milk.
ABSTRACT
Milk collected at retail markets and in schools in Connecticut in 1970-71, 1974, and 1975 was examined for flavor quality, temperature at collection, code date (last day product is intended to be offered for sale), and age of sample (days from bottling). The relationships between quality and age of sample and the processor's code date were tested. Regression analysis of 1975 samples showed that, on the average, processors overestimated shelf life by about 2 days, but this overestimate varied from 0 to 7 days for individual dairies. Although the temperature of samples collected in 1974 and 1975 was lower than in the 1970-71 sampling, there was no diminution in the percentage of samples of unsatisfactory quality.
ABSTRACT
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.
