No description available.

Thesis (MMedVet. (Vet. Public Health))--University of Pretoria, 2003. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Orientador: Paulo César Razuk / Banca: Augusto Ronchi Junior / Banca: Waldemar Gastoni Venturini Filho / Resumo: O produtor de leite de cabra, com o apoio e incentivo de entidades governamentais, privadas e ONGs; agrega tecnologia ao leite garantindo uma melhor distribuição de renda e qualidade de vida, fixando-se cada vez mais no campo. O resfriamento do leite após a ordenha é a melhor medida para retardar a proliferação natural das bactérias e sua temperatura deverá ser reduzida de 36 ºC para 4 ºC no período máximo de 2 horas em cada ordenha. O tempo transcorrido entre a primeira ordenha e seu recebimento na usina de beneficiamento deverá ser, no máximo, de 48 horas. Neste trabalho propõe-se projetar e analisar tanques de resfriamento de leite com capacidades úteis de 320, 500 e 2000 litros em aço inoxidável austenítico AISI 304, utilizando-se do coeficiente global médio (U) e das temperaturas médias de saturação do fluido de refrigeração (X) obtidos em ensaios experimentais. Um objetivo secundário foi verificar a possibilidade da utilização de caixas d'água de polietileno com a mesma capacidade dos tanques, por ser um produto acessível, de baixo custo e que atende as exigências sanitárias, visando obter um produto que possa substituir o aço inoxidável, mas descartou-se esta possibilidade, pois o fundo plano destas caixas dificultaria a retirada do produto e a limpeza. Nos cálculos envolvidos na geometria para a construção dos tanques, utilizou-se da relação entre a altura cilíndrica e o diâmetro que contemplasse respectivamente, o número... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The goat milk producer, with support and encouragement of governmental and private agencies as well as NGOs, aggregate technology to milk production ensuring a better distribution of income and life quality for all his family, making it possible the maintenance of the country life. The milk cooling ater the milking process is the best alternative to delay the natural proliferation of bacteria. The milk temperature should be reduced from 36 ºC to 4 ºC in a maximum period of time of two hours for each milking. The elapsed time between the first milking and the milk delivery in the processing plant shall be at most 48 hours. In this work, we propose to design and analyze milk cooling AISI 304 austenitic stainless ateel 320, 500 and 2000 liters tanks, using the mean global coefficient (U) and mean saturation temperatures of the refrigeration fluid (X), obtained experimentally. Besides stainless steel built tanks, accessible low cost polyethylene watertanks, with same dimensions of the steel tanks, attending the necessary sanitary requirements were used, aiming for an alternative product that can replace stainless steel. However, this possibility was rejected, because its flat basis would make it hard the product removal and its cleaning. During the geometric calculations in the manufacturing of the tanks, the relationship betwwen the cylindrical height and the diameter was defined in order to provide the golden ratio and batch square... (Complete abstract click electronic access below) / Mestre

This study was undertaken to determine the effect of acid adaptation on the survival and growth of Escherichia coli in broth and fermented goat milk. In the first phase of the study, acid resistance of E. coli O157:H7 strain UT 10 and E. coli ATCC 25922 was determined in brain heart infusion broth at pH 7.4, 4.5 and 2.5. Variations due to acid stress in the counts of both strains were determined. Alterations in the fatty acid profile due to acid adaptation were also determined. Acid adaptation enhanced the survival of both strains at pH 4.5, but neither strain could survive after 4 h at pH 2.5. At optimum growth conditions (pH 7.4), E. coli ATCC 25922 exhibited increased viability over E. coli UT 10. At pH 4.5, E. coli UT 10 was more tolerant to low pH than E. coli ATCC 25922. An increase in saturated fatty acids (SAFAs) of both AA strains was observed, indicating the importance of lipid modification in enhancing survival at low pH. In the second phase of the study, acid resistance of E. coli O157:H7 strains UT 10 and UT 15 were determined in commercial fermented at 30 °C for 24 h and stored at 7 °C for 2 days and traditional Amasi fermented for 3 days at ambient temperature (ca 30 °C). E. coli O157:H7 counts in traditional Amasi could not be detected after 3 days of challenge while those in commercial Amasi were detected at 2.7 log10 cfu/ml after the same period. The survival of acid adapted (AA) and non-adapted (NA) strains was similar in traditional Amasi while in commercial Amasi, the NA strain survived significantly better than the AA strain. The results of this study indicate that E. coli O157:H7 can survive during fermentation and storage of fermented goat milk Amasi. They also show that survival of the pathogen in a broth model differs from that in a food system. Survival of E. coli O157:H7 in fermented milk is affected by fermentation time, pH and storage temperature. The food industry should therefore adapt their processing/ preservation procedures by taking the most acid tolerant pathogenic E. coli strains into consideration in order to ensure the safety of their products. / Dissertation (MSc(Agric))--University of Pretoria, 2009. / Food Science / unrestricted

Thesis (M.Sc.). / Written for the Dept. of Animal Science. Title from title page of PDF (viewed 2008/05/28). Includes bibliographical references.

Thesis (M.Sc.)(Food Science)--University of Pretoria, 2008. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (Ph.D.(Food science))-University of Pretoria, 2009. / Includes bibliographical references. Availalble in print and online.

Thesis (M.Inst.Agrar.)(Food Production)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

This study investigated the effect of the Lactoperoxidase system (LPS) alone and in combination with pasteurisation, on the growth of Listeria monocytogenes (LM) ATTC 7644 in goat milk and goat milk cottage cheese during a shelf life of 10 days at 4 °C. Goat milk was inoculated with LM ATTC 7644 and divided into two samples, one the control and Lactoperoxidase (LP) was activated in the other sample. Both the control and LP activated samples were kept at ambient temperature for 6h. After 6h the control and LP activated samples were again divided into two and one of the respective samples was pasteurised at 72 °C for 15 s. All the four samples were analysed for LM ATTC 7644 immediately after LP activation at 0h, after 6h of LP activation and after pasteurisation. Goat milk cottage cheese was made with all four samples, i.e. control raw, control pasteurised, LP activated raw and LP activated pasteurised goat milk and analysed for LM ATTC 7644 on days 1, 2, 5, and 10. Six hours after LP activation the mean LM ATTC 7644 count for the LP activated milk decreased by log 0.5 cfu/ml where as the LM ATTC 7644 for the control increased by log 0.5 cfu/ml. The reduction of LM ATTC 7644 count in LP activated milk when compared to the control shows that goat milk lactoperoxidase is capable of reducing L. monocytogenes when stored at ambient temperatures. Furthermore, LM ATTC 7644 count in LP activated pasteurised goat milk decreased by log 1.1 cfu/ml more, compared to the control pasteurised goat milk. Therefore, pasteurisation together with LP activation may be more effective than pasteurisation alone in controlling the growth of L. monocytogenes in goat milk. For the control raw goat milk cottage cheese on day 10, the LM ATTC 7644 count was 90 % less than on first day of storage. The LP activated raw goat milk cottage cheese count followed a similar trend to the control raw goat milk cottage cheese, and reached levels of log 2.9 cfu/g on the last day of storage. The control pasteurised goat milk cottage cheese LM ATTC 7644 count on day 10 was 92 % lower compared to day 1 where as the LP activated pasteurised goat milk cottage cheese LM ATTC 7644 count was 98 % less than on day 1. The results of this study indicate that the activation of the LPS significantly (p≤0.05) decreased the LM ATTC 7644 count in goat milk, during a period of 6h. Combined pasteurisation and LP activation had a synergistic effect on the LM ATTC 7644 count in goat milk. The LM ATTC 7644 count declined in cottage cheese made from both control and LP activated goat milk. A greater decrease was observed in LP activated pasteurised goat milk cottage cheese over the storage period of 10 days at 4 °C. This combination may be used to reduce the multiplication of LM ATTC 7644 for production of safer products like goat milk and goat milk cottage cheese. / Dissertation (M Inst Agrar (Food Production and Processing))--University of Pretoria, 2007. / Food Science / M Inst Agrar / unrestricted