Graduation date: 1993

Thesis (M.S.)--Purdue University, 2003. / Includes bibliographical references (leaves [70]-80). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Purdue University, 2003. / Includes bibliographical references (leaves [70]-80).

Cooperatives are commonplace in the dairy sector throughout the developed world. A cooperative is an organization whose patrons are those who contribute the capital. Two features that distinguish a cooperative are: profits are distributed by member patronage, and member control is democratic. In theory, this organizational form cannot sustainably capture economic rents. Members adjust their production until any captured rents are eliminated, restoring the competitive solution. In British Columbia, the dairy industry is regulated by supply management. Production quotas control output, while fanner returns are guaranteed by restricting imports and administering the price. All milk is pooled, and processors need not deal directly with dairy producers. A simple model of the BC dairy industry, with farm production or processor input as the only variable, shows that the ‘competitive yardstick’ is not maintained. The industry wide milk pool decouples the cooperative from its membership. When this cooperative maximizes its patronage dividend, supply management totally separates it from its members incentives. Given that the administrative price is not set to eliminate all processing rents, the positive patronage dividend is an incentive for all farmers to join the cooperative. Simultaneously, a competing IOF can capture rents because it is buying milk at the pooi price and does not compete with the cooperative for its input needs. The financial statements of the Fraser Valley Milk Producers Cooperative Association lend support to the model. Based on performance ratios, this cooperative is behaving similar to other firms in the dairy industry, and may be capturing rents on behalf of its members. The one area of discrepancy is in the source of financing, and this can be largely explained by changing member investment preferences. Our model predicts that in B.C. the price of quota should be dependent on the return generated by our theoretical cooperative. We find that the present perfonnance of the cooperative is not a useful predictor of the quota price. However, quota price appears to be closely linked to indicators of future economic performance, and the sign of this linkage is consistent with our model. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1978 C5269 / Master of Science

During the course of ripening, Cheddar cheese frequently develops a flavor defect described as fruity. Recent work has indicated that the use of certain starter cultures ultimately results in the development of the defect as the cheese ages. The flavor compounds responsible for the defect, however, have not been elaborated. The purpose of this investigation was to isolate and identify the components responsible for the fruity flavor defect and to evaluate the role of certain cheese starter cultures in the development of the defect. Since the fruity character of the defect is apparent in the aroma of the cheese, the compounds responsible for the defect were expected to be reasonably volatile. Volatile constituents were isolated by a distillation technique from fat expressed from a typically fruity cheese by centrifugation. The volatile constituents were then separated by gas-liquid chromatography. By monitoring the odor of the effluent stream of the column, it was possible to determine which components had fruity odors, and these were subsequently identified by mass spectral analysis and coincidence of retention time with the authentic compounds. Ethyl butyrate, ethyl hexanoate, and ethyl octanoate were found to be the only compounds with detectable fruity odors. The volatiles from the fat of four cheeses possessing varying degrees of the defect and their matching non-fruity controls were analyzed by a gas entrainment, on-column trapping, gas-liquid chromatographic technique. The manufacturing and curing conditions of each fruity cheese and its matching control were identical, except for the use of different starter cultures. Ethanol, ethyl butyrate, and ethyl hexanoate were more abundant in each of the fruity samples. The approximate concentration range of these compounds was as follows: In fruity cheese; ethanol 400 to 2,040 ppm, ethyl butyrate 1.6 to 24 ppm, ethyl hexanoate 0.9 to 25 ppm. In non-fruity cheese; ethanol 36 to 320 ppm, ethyl butyrate 0.7 to 4.7 ppm, ethyl hexanoate 0.3 to 2.2 ppm. In ten commercial Cheddar cheeses selected at random from the market, the concentration of ethanol ranged from 5.5 to 620 ppm. Single-strain cultures of Streptococcus lactis, Streptococcus diacetilactis, and Streptocococcus cremoris as well as three mixedstrain commercial cultures were evaluated for ethanol and acetaldehyde production in non-fat milk medium. Among the single-strain cultures there appeared to be no correlation between ethanol production and species, although considerable variation was noted for strains within a species. The mixed-strain cultures were designated A, B, and C. Cultures B and C had been implicated in the development of the fruity flavor defect in Cheddar cheese, while culture A produced normal cheese of good quality. Cultures B and C produced approximately 40 times more ethanol than culture A when incubated in non-fat milk medium for one month at 7°C. Certain single-strain cultures and the three mixed-strain cultures were tested for their ability to reduce acetaldehyde and propanal, and to catalyze the formation of ethyl butyrate when ethanol and butyric acid were provided as substrates. Acetaldehyde and propanal were reduced to the corresponding alcohols by all cultures, but the formation of ethyl butyrate was not observed in any culture. A good correlation between high levels of ethanol and high levels of ethyl butyrate and ethyl hexanoate in the fruity cheeses suggests that the quantity of ethanol present in the cheese may determine the amount of ester formed. Further, starters resulting in the defect produced considerably more ethanol than cultures resulting in normal cheese when incubated at 7°C, a normal temperature for curing Cheddar cheese. This observation adds weight to the hypothesis that certain cultures are directly responsible for the defect. / Graduation date: 1966

Several lactic acid bacteria (LAB) of the Lactococcus, Lactobacillus, Leuconostoc and Pediococcus genera were screened for inhibition of food-borne pathogens and spoilage microorganisms in raw milk and dairy products. Listeria monocytogenes was killed by Lactococcus lactis subsp. lactis and Pediococcus pentosaceus due to their production of bacteriocin-type inhibitors. Staphylococcus aureus was not able to grow in raw milk at temperatures below 5°C even without LAB being present. Gram negative Salmonella enteritidis. Salmonella typhimurium and Escherichia coli, along with spoilage bacteria of the genus Pseudomonas were dramatically inhibited by a Lactobacillus species, designated AS-1, in raw and pasteurized milk as well as in cottage cheese. However, other LAB were not able to inhibit these organisms. Lactobacillus AS-1, did not produce hydrogen peroxide but carbon dioxide was produced. The AS-1 strain was a gram positive coccobacillus, catalase and oxidase negative and produced DL-lactic acid. It deaminated arginine and grew over a temperature range of 5°C to 45°C. It was also able to ferment glucose, galactose, fructose and lactose in addition to 17 other carbohydrates. High numbers (107 CFU/ml) of AS-1 were required to obtain complete inhibition of gram negative bacteria. A selective medium (ASLM) for Listeria monocytogenes was developed to follow the fate of this particular pathogen in association with LAB in raw milk; other selective media were not able to inhibit the growth of background flora of raw milk. ASLM was superior to four other media in allowing only the growth of the target pathogen. For the Lactococcus genus, a selective and differential agar medium (Alsan) was formulated to selectively allow growth of Lactococcus spp. and to differentiate between Lactococcus lactis subsp. lactis and the biovariety diacetylactis, based on citrate utilization. / Graduation date: 1993

No description available.

Orientador: Ricardo De Oliveira Orsi / Banca: Simone Fernandes / Banca: Hélio Almeida Ricardo / Banca: Maria Luiza Poiatti / Banca: Sarita Bonagurio Gallo / Resumo: O objetivo deste estudo foi avaliar se o nível de liberação de cortisol de ovelhas da raça Santa Inês influencia o seu desempenho e incidência de mastite. Foram utilizadas 49 ovelhas da raça Santa Inês, as quais foram submetidas a uma aplicação de ACTH exógeno (1ml/10 kg PV) para posteriormente serem divididas em 2 grupos de acordo com o nível de concentração plasmática de cortisol no pico da sua curva de liberação: AC (alto cortisol) e BC (baixo cortisol). Foram analisados o desempenho de ovelhas e cordeiros ao parto e à desmama, assim como o CMT, CCS, produção de leite, proteína e gordura do leite. Os dados foram analisados utilizando-se a análise de variância e teste de Tukey a 5% de significância. O grupo AC obteve maior média de cortisol plasmático (225,45 ± 52,08 vs 114,65 ± 36,11 ng/ml) do que o grupo BC, entretanto não houve efeito de nível de liberação de cortisol sobre as variáveis consideradas. Foi observado efeito de período (antes e após a desmama) para produção de leite (924,27 vs 232,19 ml) e proteína bruta (4,16 vs 5,79 %), respectivamente. Para CMT e CCS não foram encontradas diferenças. Concluiu-se que o nível de liberação de cortisol não influencia o desempenho nem a incidência de mastite das ovelhas da raça Santa Inês. / Abstract: The aim of this study at evaluating whether cortisol release level of Santa Ines ewes influences their performance and incidence of mastitis. It were used forty nine Santa Inês ewes, which were submitted to an application of exogenous ACTH (1ml/10 kg BW) for later be divided into 2 groups according to the level of plasma cortisol concentration at the peak of its release curve: AC (high cortisol) and BC (low cortisol). It were analyzed ewes and lambs performance for weight gain at lambing and weaning, as well as CMT, CCS, milk production, protein and fat. Data were analyzed using analysis of variance and Tukey test at 5% significance level. The AC group had higher mean plasma cortisol (225.45 ± 52.08 vs 114.65 ± 36.11 ng/ml) than the BC group, but there was no effect level of cortisol release on the variables considered. Effect was observed for period (before and after weaning) for milk production (924.27 vs 232.19 ml) and crude protein (4.16 vs 5.79%), respectively. For CMT and CCS, no differences were found. It was concluded that the level of cortisol release does not affect the performance or the incidence of mastitis of Santa Ines ewes. / Doutor