Evaluation And Improvement Of Raw And Pasteurized Fluid Milk Quality

Other Titles


Effective strategies for extending fluid milk product shelf-life by controlling bacterial growth are of economic interest to the dairy industry. To that end, the effects of addition of L-arginine, N[alpha]-lauroyl ethylester monochloride (LAE) on bacterial numbers in fluid milk products were measured. Specifically, LAE was added (125, 170, or 200 ppm) to conventionally homogenized and pasteurized 3.25% fat chocolate or unflavored milk products. The treated milks and corresponding controls were held at 6°C and plated on standard plate count (SPC) agar within 24 hours of processing and again at 7, 14, 17 and 21 d of storage. Bacterial numbers in all unflavored milk samples treated with LAE remained below the Pasteurized Milk Ordinance (PMO) limit of 4.3 log cfu/mL for the entire 21 days. Bacterial numbers in unflavored samples containing 170 and 200 ppm LAE were significantly lower than those in the untreated unflavored milk at d 17 and 21 post-processing. Specifically, bacterial numbers in the milk treated with 200 ppm LAE were 5.77 log cfu/mL lower than in untreated milk at 21 d post-processing. Bacterial numbers in chocolate milk treated with 200 ppm LAE were significantly lower than those in the untreated chocolate milk at d 14, 17 and 21. In chocolate milk treated with 200 ppm LAE, bacterial numbers were 0.9 log cfu/mL lower than in the untreated milk at 21 d post-processing. Our results show that addition of LAE to milk can reduce bacterial growth. LAE addition is more effective at controlling bacterial growth in unflavored milk than in chocolate milk. The dairy industry has a great deal of interest in tests that not only determine the quality of raw milk, but that will also help to predict the quality of the finished product processed from that raw milk. One test that has been used widely to test raw milk quality is the Preliminary Incubation (PI) test which stresses raw milk at 12.8 degrees C for 18 hours prior to enumeration. An elevated PI count has been used as an indicator that cleaning, sanitization and cooling practices on the farm are inadequate as well as an indicator of pasteurized product quality. Samples of raw milk and corresponding commercially pasteurized milk were obtained from four New York State (NYS) fluid milk processors over a one year time period from October 2007 through September 2008 to assess the overall quality of raw and pasteurized milk in NYS as well as to determine the accuracy of raw milk tests in predicting pasteurized product shelf life. Standard plate counts (SPC) and sensory quality from commercially pasteurized milk samples at day 17 post-pasteurization were compared to corresponding raw milk PI counts, with resulting R2 values of 0.2416 and 0.1007 respectively. When the confounding factor of post-pasteurization contamination (PPC) in the commercially pasteurized samples is accounted for, the R2 values for both PI versus day 17 SPC and PI versus day 17 sensory drop to 0.1972 and 0.0726 respectively. These results indicate that the PI count is not a good predictor of pasteurized milk quality, and while raw milk quality is an important factor in providing consumers with high quality product it appears that plant factors including PPC and processing conditions have a major impact on product quality. More research is needed to develop a test that can accurately and rapidly assess raw milk quality as it pertains to pasteurized product performance.

Journal / Series

Volume & Issue



Date Issued





Effective Date

Expiration Date




Union Local


Number of Workers

Committee Chair

Boor, Kathryn Jean

Committee Co-Chair

Committee Member

Worobo, Randy W.

Degree Discipline

Food Science and Technology

Degree Name

M.S., Food Science and Technology

Degree Level

Master of Science

Related Version

Related DOI

Related To

Related Part

Based on Related Item

Has Other Format(s)

Part of Related Item

Related To

Related Publication(s)

Link(s) to Related Publication(s)


Link(s) to Reference(s)

Previously Published As

Government Document




Other Identifiers


Rights URI


dissertation or thesis

Accessibility Feature

Accessibility Hazard

Accessibility Summary

Link(s) to Catalog Record