Thesis (Ph. D.)--Catholic University of America, 1941. / Bibliography: p. 150-153.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M. Sc.)(Consumer science)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

No description available.

Thesis (doctoral)--Humboldt-Universität zu Berlin, 2000. / Includes bibliographical references (p. 128-140).

Orientador: Ana Maria Centola Vidal / Banca: Heidge Fukumasu / Banca: Vera Letticie de Azevedo Ruiz / Banca: Naia Carla Marchi de Rezende Lago / Banca: Rachel Zoccal Saba / Resumo: As espécies do grupo do Bacillus cereus são comumente ocorrentes na cadeia produtiva de leite e derivados e frequentemente estão envolvidas em doenças transmitidas por alimentos. Constituem uma preocupação constante à indústria de lácteos, por conta de sua capacidade de formar biofilmes em superfícies sólidas, ocasionando a contaminação persistente dos produtos processados e representando risco à saúde pública. Objetivou-se neste estudo verificar a distribuição e ocorrência de linhagens e genes específicos relacionados à formação de biofilmes de Bacillus cereus isolados dos diversos estágios da cadeia produtiva de leite e produtos lácteos, classifica-los quanto à potencialcialidade em formar biofilmes, e ainda, avaliar a atuação e eficiência do ácido peracético e do hipoclorito de sódio junto ao sistema "clean in place", simulado em escala piloto, sobre biofilmes formados em superfícies de aço inoxidável em contato com o leite. Para tanto, foram isolados microrganismos do grupo do Bacillus cereus de propriedades leiteiras, industrias e produtos lácteos, identificados genes específicos (sipW, tasA, Spo0A e PlcR) por sequenciamento genômico e avaliada a capacidade de formar biofilmes em microplacas de poliestireno. Selecionou-se um isolado sabidamente produtor de biofilmes, e por meio de contaminação experimental, induziu-se a adesão em superfícies de cupóns de aço inoxidável, em três circunstâncias distintas, incluindo contaminação por esporos, células vegetativas, e contamina... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Species included in B. cereus group are widely distributed in dairy environment and were frequently involved in foodborne diseases. They are considered as a concern for dairy industries despite they pose a risk for public health, also despite the able to biofilm formation on stainless steel surfaces, causing the persistent contamination of processed dairy products. This study aimed to investigate if specific strains and genes for biofilm formation are significantly distributed and overpresented in distinct stages of dairy production chain, classifies the potential for biofilm formation, and evaluate the performance and efficiency of peracetic acid and sodium hypochlorite, on a pilot scale simulated clean in place, on biofilms in the stainless steel surfaces in contact with milk. Bacillus cereus microorganisms from dairy farms, industries and dairy products were identified, specific genes (sipW, tasA, Spo0A and PlcR) were identified by genomic sequencing and to form biofilms was performed using polystyrene microplates. Was selected one isolate known to produce biofilms, and by means of experimental contamination, adhesion was induced on stainless steel coupon surfaces, in three different circumstances, including spore contamination, vegetative cells, and contamination followed by pasteurization. In the sequence, the coupons were subjected to the action of peracetic acid and sodium hypochlorite, applying them to the clean in place system, performed on a pilot scale. Among 69 is... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2015-12-10T14:24:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-18. Added 1 bitstream(s) on 2015-12-10T14:31:06Z : No. of bitstreams: 1 000852078.pdf: 482669 bytes, checksum: 111a6215a95c4ef29cb134b9b69c3e40 (MD5) / 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. / 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.

CAPES / A Mesorregião do Sudoeste Paranaense se destaca pela atividade leiteira, com produção, industrialização e comercialização de derivados. O uso de bactérias láticas endógenas vem ganhando o mercado mundial com pesquisas e elaboração de produtos, e despertando o interesse de Instituições de Ensino do Brasil. Este trabalho teve como objetivo isolar, caracterizar e identificar a microbiota lática do leite cru, para desenvolver um fermento endógeno e, a partir deste, elaborar o Queijo Típico. Foram desenvolvidos dois fermentos, compostos pelas bactérias Streptococcos thermophillus e Lactobacillus delbrueckii sp. bulgaricus. Os fermentos foram testados em dois laticínios da região, utilizando leite pasteurizado e os conservantes nitrato de sódio e a enzima lisozima. Os queijos elaborados foram submetidos a análises para o acompanhamento das modificações durante a maturação (30, 60 e 180 dias) e todas as amostras avaliadas exibiram características físico-químicas e microbiológicas de acordo com a legislação brasileira, podendo ser classificados, de um modo geral, como queijos de média umidade, variando de 40,71 a 42,44 g/100 g (30 dias), 35,37 a 40,28 g/100 g (60 dias) e 33,63 a 38,63 g/100 g (180 dias), de acordo com o teor de matéria gordurosa no extrato seco classificam-se em gordos, 40,37 a 48,80 (g/100 g) (30 dias), 44,42 a 48,25 (g/100 g) (60 dias) e 45,30 a 49,80 (g/100 g) (180 dias). As proteínas (g/100 g) variaram de 20,57 a 23,95 g/100 g (30 dias), 21,88 a 24,71 (60 dias), 23,52 a 30,57 (180 dias), os lipídeos entre 20,57 a 23,95 (30 dias), 24,71 a 21,88 (60 dias), e 30,57 a 23,52 (180 dias). Os teores de cinzas ficaram entre 2,99 a 4,88 (g/100 g) (30 dias), 4,10 a 5,00 (g/100 g) (60 dias) e 4,58 a 5,19 (g/100 g) (180 dias), atividade de água (Aw) entre 0,9531 a 0,9635 (30 dias), 0,9366 a 0,9547 (60 dias) e 0,9284 a 0,9380 (180 dias). As análises de textura apontaram que o queijo desenvolvido, no decorrer dos períodos de maturação, apresentou aumento da dureza, onde o menor valor aos 30 dias estava em 18377,19 g passando aos 180 dias para um valor máximo de 27401 g. A elasticidade, que aos 30 dias apresentava-se em 0,82, passou a 0,88 aos 180 dias. A mastigabilidade de 11412,92 (30 dias) passou para 5116,76 (180 dias). A coesividade de 0,67 (30 dias) ficou em 0,20 (180 dias). A adesividade que era de -205,45 (30 dias) passou para -25,04 (180 dias) e a resistibilidade que inicialmente era de 0,21 (30 dias) ficou com 0,04 (180 dias). Em relação à análise de cor, as amostras apresentaram alta luminosidade (L*) chegando a ter aos 180 dias (73,51 ± 3,62 a 79,75 ± 0,56), com predominância da componente amarela (b*) (34,10 ± 0,55 a 36,81 ± 0,29), e amostras dentro do espectro verde (a*) (-7,40 ± 0,06 a -7,82 ± 0,21), com pequenas variações entre si. As análises sensoriais do queijo apontaram para aceitação diante dos provadores. Este trabalho representa uma das etapas acerca da utilização do fermento endógeno na fabricação de um Queijo Típico Regional, que recebeu a denominação de “Santo Giorno” e contribuiu para a compreensão das variações e interações dos componentes fisíco-químicos e microbiológicos no desenvolvimento de um produto de elevada qualidade. / The Greater Region Southwest of Paraná stands out for dairy farming, with production, processing and trading of derivatives. The use of endogenous lactic acid bacteria is gaining global market research and product development is attracting the interest of Educational Institutions in Brazil. This work aimed to isolate, identify and characterize the lactic microflora of raw milk, to develop endogenous starter culture, and using it, prepare the Cheese Typical. Two starters cultures, Streptococcus thermophillus compounds by bacteria and Lactobacillus delbrueckii sp bulgaricus were developed. The starter culture were tested in two dairy region, using pasteurized milk, preservatives sodium nitrate and lysozyme enzyme. The elaborate cheeses were subjected to analysis for the monitoring of changes during maturation (30, 60 and 180 days) and all samples exhibited physicochemical and microbiological characteristics according to Brazilian legislation. They can be classified broadly as cheese medium humidity ranging from 40.71 to 42.44 g/100 g (30 days), from 35.37 to 40.28 g/100 g (60 days), and from 33.63 to 38.63 g/100 g (180 days), according to the content of fatty matter in dry matter, cheeses can be classified as fat, from 40.37 to 48.80 (30 days), from 44.42 to 48.25 (60 days) and 45.30 to 49.80 (180 days). Proteins ranged from 20.57 to 23.95 g/100 g (30 days), from 21.88 to 24.71 g/100 g (60 days), from 23.52 to 30.57 g/100 g (180 days), lipids between 20.57 to 23.95 g/100 g (30 days), from 24.71 to 21.88 g/100 g (60 days), and from 30.57 to 23.52 g/100 g (180 days). The ash content ranged from 2.99 to 4.88 (30 days), from 4.10 to 5.00 (60 days) and from 4.58 to 5.19 (180 days) the water activity from 0.9531 to 0.9635 (30 days), 0.9366 to 0.9547 (60 days) and 0.9284 to 0.9380 (180 days). Textural analyzes indicated that the cheese developed during periods of maturation, showed an increase in hardness, where the lowest value at 30 days was at 18377.19 g passing the 180 days to a maximum value of 27401 g. The elasticity at 30 days showed that in 0.82, went 0.88 at 180 days. The chewiness of 11412.92 (30 days) increased to 5116.76 (180 days). The cohesiveness of 0.67 (30 days) stood at 0.20 (180 days). The adhesiveness which was -205.45 (30 days) increased to -25.04 (180 days) and the resistivity which was initially 0.21 (30 days) was 0.04 (180 days). Regarding the analysis of the samples showed high color brightness (L*), coming to have 180 days (73.51 ± 3.62 to 79.75 ± 0.56), with a predominance of yellow component (b*) (34.10 ± 0.55 to 36.81 ± 0.29), and samples within the green spectrum (a*) (-7.40 ± 0.06 and -7.82 ± 0.21), showed minor variations. The sensory analysis of Cheese Typical pointed to acceptance by the panelists. This work represents one of the steps of using endogenous starter culture in a cheese, which was called as "Santo Giorno", and contributed to understanding the variations and interactions of physico-chemical and microbiological development of a regional product, with high quality components.

Survival of Escherichia coli O157:H7 in fermented dairy products has been attributed to acid-adaptation. Acid-adaptation enhances resistance to extreme acid pH and confers cross-protection to heterologous stresses. This study sought to investigate whether acid-adaptation confers cross-protection to lactoperoxidase (LP) system and lactic acid in Tryptone Soy Broth (TSB), and to determine the mechanism of cross-protection. Subsequently, cross-protection of acid-adapted E. coli O157:H7 to the combination of LP activation, heat and lactic acid treatments was determined in fresh goat milk. Finally, the effect of LP activation and E. coli O157:H7 survival on acid production during fermentation of traditional and commercial goat milk was investigated with indigenous cultures and single strain lactic acid bacteria (LAB) respectively. Acid-adapted E. coli O157:H7 strain UP10 showed high acid-resistance at pH levels 4.0 and 5.0 for up to 24 h in TSB at 25°C compared to non-adapted E. coli O157:H7. Acid-adaptation also conferred cross-protection against activated LP system and lactic acid challenge at pH 4.0 and 5.0. Results from fatty acid analysis and quantitative real time Polymerase Chain Reaction (RT-PCR) indicated that sigma S (RpoS)-independent systems were responsible for acid-resistance and cross-protection in TSB. Increase in the saturation of fatty acids, increased expression of outer membrane porin, OmpC, and activation of the glutamate decarboxylase system contributed to acid-resistance and cross-protection. Growth of acid-adapted E. coli O157:H7 strains UP10 and 1062 were inhibited in fresh goat milk compared to the non-adapted cells. Nonetheless, strain 1062 showed better growth and resistance to activated LP in fresh goat milk compared to strain UP10. LP activation alone did not significantly inhibit either acid-adapted or non-adapted E. coli O157:H7, but it sensitized E. coli O157:H7 cells to sub-lethal heat treatment at 55 and 60°C. The combination of heat treatment at 60°C, LP activation and lactic acid at pH 5.0 had a greater inhibitory effect on both acid-adapted and non-adapted E. coli O157:H7, but the acid-adapted strains displayed cross-protection against combined treatments. This indicates that non-adapted E. coli O157:H7 can survive a certain threshold of stresses unscathed. Below that threshold, acid-adaptation may be detrimental to survival. LP activation did not inhibit growth and acid production by single strain and indigenous LAB in the processing of commercial and traditional fermented goat milk products. LP activation however inhibited E. coli O157:H7 in both the commercial and traditional goat milk products although E. coli O157:H7 had become acid-adapted during the fermentation process. E. coli O157:H7 inhibition could be due to the combination of LP activation, low pH, fermentation time and antimicrobial compounds present in the milk or produced by the LAB during milk fermentation. Results from this study suggest that while acid-adaptation protects E. coli O157:H7 under harsh conditions, it can sensitize E. coli O157:H7 to sub-lethal stresses that does not require acid-adaptation for survival. On the other hand, non-adapted E. coli O157:H7 could become acid-adapted in food at mild acid pH which may enhance prolonged survival in such foods. / Thesis (PhD)--University of Pretoria, 2010. / Food Science / unrestricted

No description available.