Reduction of pasteurization temperature leads to lower bacterial outgrowth in pasteurized fluid milk during refrigerated storage: a case study.

Bacterial numbers over refrigerated shelf-life were enumerated in high-temperature, short-time (HTST) commercially pasteurized fluid milk for 15 mo before and 15 mo after reducing pasteurization temperature from 79.4°C (175°F) [corrected] to 76.1°C (169°F). Total bacterial counts were measured in whole fat, 2% fat, and fat-free milk products on the day of processing as well as throughout refrigerated storage (6°C) at 7, 14, and 21 d postprocessing. Mean total bacterial counts were significantly lower immediately after processing as well as at 21 d postprocessing in samples pasteurized at 76.1°C versus samples pasteurized at 79.4°C. In addition to mean total bacterial counts, changes in bacterial numbers over time (i.e., bacterial growth) were analyzed and were lower during refrigerated storage of products pasteurized at the lower temperature. Lowering the pasteurization temperature for unflavored fluid milk processed in a commercial processing facility significantly reduced bacterial growth during refrigerated storage.

Results from raw milk microbiological tests do not predict the shelf-life performance of commercially pasteurized fluid milk.

Analytical tools that accurately predict the performance of raw milk following its manufacture into commercial food products are of economic interest to the dairy industry. To evaluate the ability of currently applied raw milk microbiological tests to predict the quality of commercially pasteurized fluid milk products, samples of raw milk and 2% fat pasteurized milk were obtained from 4 New York State fluid milk processors for a 1-yr period. Raw milk samples were examined using a variety of tests commonly applied to raw milk, including somatic cell count, standard plate count, psychrotrophic bacteria count, ropy milk test, coliform count, preliminary incubation count, laboratory pasteurization count, and spore pasteurization count. Differential and selective media were used to identify groups of bacteria present in raw milk. Pasteurized milk samples were held at 6°C for 21 d and evaluated for standard plate count, coliform count, and sensory quality throughout shelf-life. Bacterial isolates from select raw and pasteurized milk tests were identified using 16S ribosomal DNA sequencing. Linear regression analysis of raw milk test results versus results reflecting pasteurized milk quality consistently showed low R(2) values (<0.45); the majority of R(2) values were <0.25, indicating small relationship between the results from the raw milk tests and results from tests used to evaluate pasteurized milk quality. Our findings suggest the need for new raw milk tests that measure the specific biological barriers that limit shelf-life and quality of fluid milk products.

High temperature, short time pasteurization temperatures inversely affect bacterial numbers during refrigerated storage of pasteurized fluid milk.

The grade A Pasteurized Milk Ordinance specifies minimum processing conditions of 72 degrees C for at least 15 s for high temperature, short time (HTST) pasteurized milk products. Currently, many US milk-processing plants exceed these minimum requirements for fluid milk products. To test the effect of pasteurization temperatures on bacterial numbers in HTST pasteurized milk, 2% fat raw milk was heated to 60 degrees C, homogenized, and treated for 25 s at 1 of 4 different temperatures (72.9, 77.2, 79.9, or 85.2 degrees C) and then held at 6 degrees C for 21 d. Aerobic plate counts were monitored in pasteurized milk samples at d 1, 7, 14, and 21 postprocessing. Bacterial numbers in milk processed at 72.9 degrees C were lower than in milk processed at 85.2 degrees C on each sampling day, indicating that HTST fluid milk-processing temperatures significantly affected bacterial numbers in fluid milk. To assess the microbial ecology of the different milk samples during refrigerated storage, a total of 490 psychrotolerant endospore-forming bacteria were identified using DNA sequence-based subtyping methods. Regardless of processing temperature, >85% of the isolates characterized at d 0, 1, and 7 postprocessing were of the genus Bacillus, whereas more than 92% of isolates characterized at d 14 and 21 postprocessing were of the genus Paenibacillus, indicating that the predominant genera present in HTST-processed milk shifted from Bacillus spp. to Paenibacillus spp. during refrigerated storage. In summary, 1) HTST processing temperatures affected bacterial numbers in refrigerated milk, with higher bacterial numbers in milk processed at higher temperatures; 2) no significant association was observed between genus isolated and pasteurization temperature, suggesting that the genera were not differentially affected by the different processing temperatures; and 3) although typically present at low numbers in raw milk, Paenibacillus spp. are capable of growing to numbers that can exceed Pasteurized Milk Ordinance limits in pasteurized, refrigerated milk.

Short communication: bacterial ecology of high-temperature, short-time pasteurized milk processed in the United States.

To determine the microbial ecology of pasteurized milk within the United States, 2% fat pasteurized fluid milk samples were obtained from 18 dairy plants from 5 geographical areas representing the Northeast, Southeast, South, Midwest, and West. Of the 589 bacterial isolates identified using DNA sequence-based subtyping methods, 346 belonged to genera characterized as gram-positive endospore-forming bacteria (i.e., Bacillus and Paenibacillus). Of the 346 gram-positive endospore-forming bacteria isolated in the present study, 240 were classified into 45 allelic types identical to those previously identified from samples obtained in New York State, indicating the widespread presence of these microbes in fluid milk production and processing systems in the United States. More than 84% of the gram-positive spore-forming isolates characterized at d 1, 7, and 10 were of the genus Bacillus, whereas more than 92% of isolates characterized at d 17 of shelf life were of the genus Paenibacillus, indicating that the predominant gram-positive spoilage genera shifts from Bacillus spp. to Paenibacillus spp. during refrigerated storage.

[Angiosarcoma of the breast]. / Sull'angiosarcoma della mammella.

Two cases of angiosarcoma of the breast observed in 1981 and 1982 are reported; one of these is still living, but with local recurrence. The pathogenesis, classification, prognosis and therapy of this malignant tumor are analysed. The review of the literature and personal experience seem to suggest that the treatment of choice should be surgical with complementary radiotherapy.