The basic problem confronting the dairy industry today is one of utilizing its total fluid milk production. During recent years the industry has witnessed a general decrease in per capita consumption of dairy products while per capita production has remained fairly constant and in amounts approximating the average for the past 16 years (Table 2 ). As a result the dairy industry has produced a surplus of fluid milk and manufactured dairy products. The Federal Government, under its price support program, has been the ultimate recipient of these surpluses and now possesses huge warehouse stocks. The cost to the Federal Government and to the taxpayer has been great, resulting in an intense desire by both the Federal Government and the dairy industry to take steps to alleviate this condition. The following study is undertaken with the hope that the findings from it may provide the dairy industry with information which, in some small way, may contribute a partial solution to this problem.

Many of the fluid milk processing plants in Utah are relatively small. The typical small plant in Utah is generally family operated with some hired help. Although most of the small plants are individually owned, some are operated as partnerships. Often the same man picks-up, processes, and then delivers the milk. Some of the processors also own dairy herds. In these cases, the same man performs all the functions necessary to carry the milk products from the farm to the consumer's door. It is not uncommon to find the plant owner and manager performing all these duties himself.

Dairying is one of the most important agricultural enterprises in Utah. Income from the sale of dairy products by farmers within the state comprises about fifteen percent of the total farm income. Milk and its products are an essential part of the diet of practically all consumers. Its widespread use makes it a commodity that should receive spectial consideration and study. The continued growth of the industry depends upon how well it can meet the demands of the consumer in supplying quality dairy products at reasonable prices. The problems that need particular attention to bring about continued growth are efficient production on the farms, programs to increase the demand for and consumption of milk, sound price policies, seasonality of milk prouction, price spreads for milk of different grades and uses, and reduction in marketting.

Nisin is a naturally occurring food antimicrobial that inhibits many Grampositive pathogens, including Listeria monocytogenes, a bacterial pathogen responsible for ~500 deaths in the U.S. annually. Factors known to counteract the nisin activity in a food matrix include: antimicrobial interaction with food components, insolubility, protease inactivation, and target cell-driven envelope modifications. Encapsulating nisin in liposomes can help protect nisin functionality by regulating its introduction to the external environment. The objectives of this study were to determine the encapsulation efficiency (%EE) of nisin within liposomes as a function of encapsulation method and the capacity of liposomal nisin to inhibit L. monocytogenes in fluid milk. Phosphatidylcholine (PC) and phosphotidyl-DL-glycerol (PG) were used to prepare three lipid molar formulations: PC, PC/PG 7:3, and PC/PG 6:4 (mol.%). Liposomes were formulated to entrap the self-quenching fluorophore calcein and nisin. Unencapsulated analyte was removed via size-exclusion chromatography, and percent EE was determined. To determine antilisterial activity of liposomes, fluid milk samples containing L. monocytogenes (4 log10 CFU/mL) in combination with liposomal or unencapsulated nisin at 50 IU/mL were mixed and aerobically stored at 5 degrees C and 20 degrees C. Surviving L. monocytogenes were enumerated via plating on a non-selective microbiological medium after 0, 1, 3, 6, 12, 24, 48, and 72 hours of incubation. Encapsulation of nisin via extrusion resulted in a mean EE% of 84.20%, 77.33% and 80.78% for PC, PC/PG 7:3, and PC/PG 6:4 liposomes, respectively. Freeze-thaw cycling formed liposomes without detectable fluorophore entrapment. L. monocytogenes populations grew to 5 log10 CFU/mL after 72 hours at 5 degrees C and 8 log10 CFU/mL at 20 degrees C after 48 hours. Unencapsulated nisin exerted statistically greater inhibition of Listeria in skim milk compared to liposomal nisin, regardless of incubation temperature. No statistically significant differences in Listeria populations exposed to free or encapsulated nisin in whole milk were observed at either incubation temperature. Results indicate storage temperature and presence of milk fat exert greater influence then nisin delivery (free vs. encapsulated) over Listeria inhibition. Further research is needed to confirm these findings and develop more effective means of liposome entrapment of nisin for the inhibition of foodborne bacterial pathogens.

The relationship among consumer acceptability, descriptive sensory attributes, and shelf-life was determined for 2 % milk pasteurized at 77, 79, 82, or 85?aC. Pasteurization temperature had no effect (p>0.05) on shelf-life. Consumers preferred (p<0.05) 79?aC over other treatments on day 0; however, six days post-pasteurization 79?aC milk was only preferred (p<0.05) over 77?aC. Consumers were grouped into eight clusters based on product liking for both day 0 and 6 evaluations. The largest cluster liked all pasteurization treatments, and 79?aC was highly acceptable to all consumers that liked milk. Similar sensory descriptors indicated the end of shelf-life for all pasteurization treatments even though treatments could be differentiated by descriptors on day 0. This research reveals that altering pasteurization temperature from 79?aC may cause a decrease in consumer acceptability to some consumers. Altering pasteurization temperature does not affect shelf-life or sensory descriptors and volatile compound profiles at the end of shelf-life.

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