No description available.

A continuous flow microwave heating system was set up by using one domestic microwave oven (1000W nominal output at 2450MHz). Water was run through the coil centrally located inside the oven cavity for microwave heating. Microwave absorption efficiency was evaluated by measuring inlet and outlet temperatures of coil as a function of system variables. In order to optimize the coil configuration, the influence of tube diameter (6.4, 7.9 and 9.7mm); initial temperature (10, 20 and 30 ºC); number of turns (3.5, 4.5 and 5.5); coil diameter (61.5, 88, 102, 121 and 153 mm) and pitch (16, 18, 20, 22 and 24mm) were evaluated, respectively at different flow rates (240, 270, 300, 330 and 360ml/min). In helical systems, Dean number is used as a measure of secondary flow which enhances mixing of the fluid providing uniform heating even under laminar flow conditions. Results showed that microwave absorption efficiency was a compromise between coil volume and Dean number. Therefore, a helical coil (110 mm high) with a coil diameter of 108 mm, tube diameter of 8.2 mm, 5.5 turns demonstrated the highest efficiency, fast heating rate, more uniform heating and less temperature fluctuations. The optimized coil configuration parameters were used subsequently to set up continuous-flow microwave heating system.

Orientador : Jose Satiro de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos e Agricola / Made available in DSpace on 2018-07-17T16:26:26Z (GMT). No. of bitstreams: 1 Prata_LuizFrancisco_M.pdf: 25047113 bytes, checksum: 929fcb9f022bcc9e6a2e25a2e4738ae7 (MD5) Previous issue date: 1984 / Resumo: Partindo-se da importância do controle microbiológico do leite recebido na plataforma das indústrias de laticínios, a pesquisa de provas específicas que ofereçam resultados rápidos e compatíveis com a perecibilidade do produto, tem sido o objetivo do serviço de inspeção sanitária. Nesse aspecto, não encontramos, sendo utilizado em nosso meio, um teste que ofereça resultados que permitam o controle efetivo da matéria prima antes que esta entre na linha de processamento.No presente trabalho foi, então, estudado o método de contagem microscópica de microrganismos, com a intenção de comprovar a sua aplicabilidade como método rápido para o controle microbiológico do leite ao chegar à plataforma. Os resultados alcançados permitiram concluir que esse método se correlacionou muito bem com a contagem padrão em placas, tendo se comportado, também, de forma semelhante ao método de redução do azul de metileno. A aplicação do método microscópico na avaliação da qualidade microbiológica de 319 amostras de leite cru, incluindo leite tipo ¿B¿ apresentou resultados que permitiram recomendá-lo como teste rápido para o controle de qualidade a nível de plataforma das indústrias de laticínios. Mostrou-se útil, também, no fornecimento de informações adicionais importantes, como por exemplo na detecção de leite mastítico. Ressalta-se, ainda, que sua aplicação a leite pasteurizado permitiu uma indicação da qualidade microbiológica do leite antes de ser submetido ao tratamento térmico / Abstract: The microbiological quality is the starting point for the milk quality control in the receiving platform of the dairy industry, therefore the search for specific rapid tests has been the airn of resarchers envolved in milk quality inspection. In Brazil we have not found a microbiological test being used which could effectively evaluate the raw milk quality before it enters the processing line. In the present research work it was studied the direct microscopic count method to show its applications as a rapid test for contoling the milk quality in our brazilian industrues. The results indicated a very good correlation between the microscopic. Count and the standard plate count. As a quality control test the microscopic method was equivalent to the methylene blue reduction test. In assessing the microbiological quality of 319 samples of raw milk, including also type B milk, the microscopic count method proved to be a very good rapid test for controlling the raw milk quality in the dairy industry. This method also gave additional informations regarding the milk quality, like for instance the indication of mastitic milk. It could also be pointed that the microscopic count when applied to pasteurized milk gives a good idea of the microbiological quality of this milk right before it's pasteurization / Mestrado / Mestre em Tecnologia de Alimentos

No description available.

Master of Science

Made available in DSpace on 2014-06-11T19:27:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-03-02Bitstream added on 2014-06-13T18:56:01Z : No. of bitstreams: 1 sartori_lca_me_jabo.pdf: 309501 bytes, checksum: f65ecbb362c11cf287ceffd861806be4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A mastite representa um dos mais sérios problemas existentes nas fazendas de leite. Os objetivos deste estudo foram identificar leveduras envolvidas nos casos de mastite bovina; avaliar a sensibilidade in vitro de cepas de Candida spp. frente a quatro desinfetantes utilizados no pré e pós-dipping e avaliar a resistência destas leveduras frente à pasteurização e fervura. Cinquenta e cinco amostras (12,8%) foram positivas para o gênero Candida. As espécies mais isoladas foram C. krusei (34,6%), C. parapsilosis (25,4%), C. tropicalis (18,2%) e C. albicans (12,8%). As drogas utilizadas foram clorexidina (2,0%), iodo (0,8%), iodo glicerinado (0,8%) e hipoclorito de sódio (1,0%) em 4 intervalos específicos de tratamento (15″, 30″, 60″ e 300″). Cem por cento das cepas de Candida foram sensíveis a clorexidina nos tempos de 30″, 60″ e 300″, ao iodo glicerinado em 60″ e 300″, ao hipoclorito de sódio em 60″ e 300″ e ao iodo apenas em 300″. Em relação aos tratamentos térmicos, a pasteurização rápida foi o procedimento no qual houve maior índice de resistência (64,44%) por parte das estirpes de leveduras. A mastite provocada por fungos está se tornando um problema crescente devido ao aumento da participação deste microrganismo no desenvolvimento de mastite em bovinos. Além disso, resistência apresentada ao tratamento térmico pelas cepas de Candida representa um problema para o consumo de leite, significando um risco para a saúde pública. Uma conclusão adicional é a importância da realização periódica de avaliações de sensibilidade dos microrganismos aos desinfetantes utilizados, de forma a garantir a eficácia da desinfecção dos tetos / Mastitis is one of the most serious problems in dairy farms. The objectives of this study were to identify yeasts involved in cases of bovine mastitis; evaluate the in vitro susceptibility of strains of Candida spp. Against four disinfectants used in the pre and post-dipping and evaluate the resistance of these strains before pasteurization and boiling. Fifty-five samples (12,8%) were positive for Candida. The most isolated species were C. krusei (34,6%), C. parapsilosis (25,4%), C. tropicalis (18,2%) and C. albicans (12,8%). As active drugs were used chlorhexidine (2,0%), iodine (0,8%), glycerin iodine (0,8%) and sodium hypochlorite (1,0%) at specific intervals of four treatment (15, 30, 60 and 300). One hundred percent of Candida was found to be sensible to chlorhexidine at 30″, 60″, and 300″, to iodine glycerin at 60″ and 300″, to sodium hypochlorite at 60″, and 300″, to iodine only at 300″. In relation to thermal treatments, pasteurization was the quick procedure in which there was a higher resistance index (64,44%) by yeast strains. Moreover, t he resistance of Candida spp. strains after thermal treatment presents a problem for milk consumption what represents a potential risk for public health. A further conclusion was that it is important to undertake a periodic evaluation of the sensibility of microorganisms to the disinfectants commonly used, to guarantee the efficacy of the process of teat disinfecting

The causes of acid liquefaction in a high grade pasteurized milk were investigated. 1. Liquefying milk produced much less acid and had a much lower plate count than normal milk. 2. <i>Bacillus albolactis</i> was found regularly in the milk. It made up a much larger percentage of the total flora in liquefying than in normal milk. 3. Associated growth experiments showed that <i>Strep. lactis</i> could control the liquefying activities of <i>Bacillus albolactis</i>. 4. Pasteurization experiments showed that milk heated for 20 minutes at temperatures higher than 61°C. would undergo acid liquefaction. This appeared to be due to the increase in the percentage of <i>Bacillus albolactis</i>. 5. Inoculation of pasteurized samples with <i>Strep. lactis</i> prevented acid liquefaction. 6. Comparison with a type species showed that the strains of <i>Strep. lactis</i> repeatedly isolated from the milk studied were of the <i>tardus</i> variety. 7. The liquefaction was probably primarily due to an increased percentage of <i>Bacillus albolactis</i> brought about by pasteurization; the lack of the type of species of <i>Strep. lactis</i> and the absence of lactobacilli might also have been contributing factors. / Master of Science

Yes / A milk pasteurization process, a nonlinear process and multivariable interacting system, is difficult to control by the conventional on-off controllers since the on-off controller can handled the temperature profiles for milk and water oscillating over the plant requirements. The multi-variable control approach with model predictive control (MPC) is proposed in this study. The proposed algorithm was tested for control of a milk pasteurization process in three cases of simulation such as set point tracking, model mismatch, difference control and prediction horizons, and time sample. The results for the proposed algorithm show the well performance in keeping both the milk and water temperatures at the desired set points without any oscillation and overshoot and giving less drastic control action compared to the cascade generic model control (GMC) strategy.

Alkaline phosphatase (ALP) is a natural milk enzyme. It has been used as reporter for process controls in food industry. Since ALP denatures at pasteurization temperature (at 63&deg / C or 72&deg / ) its detection in milk confirms the unproper pasteurization. There are different detection procedures such as colorimetric, fluorometric methods and immunoassays for ALP in milk. However, they are time consuming processes and require specific instruments and qualified staff. In this study, new, semiquantitative, disposable, cheap and practical paper bioreporter have been developed for ALP detection. In optimization studies, 1mg/mL p-NPP in 0.1 M glycine buffer at pH 9.5 and 0.5 mg/mL bromocresol green in 1.0 M Tris-HCl buffer at pH 9.5 were determined as optimum for ALP bioreporter as a result of visual inspection and green color intensity analyses.The effects of samples temperature and pH of on the response of bioreporter were tested. Milk samples at pH 5.0, 5.5, 6.0 and 6.5 and milks stored at 37&deg / C, room temperature and 4&deg / C did not affect the response of bioreporter. Also the response of bioreporter against milk samples from different animals (cattle, sheep and goat) and cow&rsquo / s milk from different location in Turkey were evaluated. The appropriate responses were observed by bioreporter. Whatman filter papers, cotton and bandage were used as support materials to construct bioreporter and Whatman filter papers were selected as the most applicaple support material. Finally, stability tests were carried out at 4&deg / C and room temperature and 40 days at 4&deg / C was determined as shelf life of bioreporter.

Increasing interest has been shown in the irradiation sterilization and irradiation pasteurization of foods, but problems of off-flavors and odors are still unsolved, especially in the case of dairy products. From the flavor chemistry point of view, milk lipids are very highly susceptible to irradiation effects. Therefore, this investigation was designed to study some irradiation induced reactions involving flavor changes in the milk fat and to identify the volatile components produced in the milk fat upon irradiation. Milk fat, prepared from raw sweet cream and washed free of phospholipids, was first irradiated in the presence of air and under vacuum in glass vials at 4.5 Mrad with gamma rays from cobalt-60. The irradiation resulted in increase in TBA number, peroxide value, total monocarbonyls, bleaching of color, slightly rancid and typical candle-like off-flavors. Free fatty acids were also produced upon irradiation. The changes were more drastic in air along with production of a slight oxidized flavor. The monocarbonyls identified by column and paper chromatographic methods in irradiated milk fat include: C₁ through C₁₂, C₁₄ , and C₁₆ n-alkanals; C₃ through C₉, C₁₁, C₁₃ and C₁₅ alk-2-ones with only traces of C₆ and C₈ alk-2- ones; and C₅, C₆, C₉, and C₁₂ alk-2-enals. Irradiation of milk fat that had been dried over calcium hydride also caused free fatty acid production, especially short chain fatty acids. Methyl octanoate treated with calcium hydride and irradiated at 1.5, 3.0, 4.5, and 6.0 Mrad yielded small quantities of free octanoic acid, confirming that irradiation caused fission of the ester linkage even when traces of water were removed. The quantities of octanoic acid formed increased with increasing dose of irradiation. For identification of volatile components, the milk fat was irradiated in 307x409 'C' enameled cans under vacuum. The headspace analysis showed some air still left in the cans. Irradiation resulted in consumption of oxygen and production of hydrogen, carbon monoxide, carbon dioxide, and methane as identified in the headspace gases. The volatiles were isolated from the irradiated and control milk fats by low temperature, vacuum steam distillation at 40°C and 1-2 mm Hg. The volatile components were then extracted from the aqueous distillate with ethyl ether. The ethyl ether extract exhibited the typical candle-like defect. The ethyl ether concentrate was analyzed by combination of GLC and fast-scan mass spectrometric techniques. Identification of various components was achieved on the basis of mass spectral data and coincidence of gas chromatographic retention times. In the case of the components for which only GLC t[subscript r]/t[subscript r] evidence was available or the mass spectra obtained were not satisfactory, the identity assigned was only tentative. The volatile compounds that were positively identified to be present in irradiated milk fat are given below: n-Alkanes C₅ through C₁₇ 1-Alkenes C₅, C₇ through C₁₇ Fatty acids C₄, C₆, C₈ and C₁₀ n-Alkanals C₅ through C₁₁ Others γ-decalactone, δ-decalactone, 2-heptanone, benzene, ethyl acetate, chloroform, and dichlorobenzene. The tentative identification was obtained for the following compounds: γ-lactones C₆ and C₈ δ-lactones C₆, C₈, C₁₁, and C₁₂ 1, ?-alkadienes C₁₀, C₁₁, C₁₂, C₁₆ and C₁₇ iso-alkanes C₁₀, C₁₁, C₁₂, and C₁₃ Others methyl hexanoate, 2-hexanone, 4-heptanone and n-dodecanal. The compounds present in unirradiated control milk fat included: short chain fatty acids (C₄, C₆, C₈, and C₁₀), C₈, C₁₀, and C₁₂ δ-lactones, 2-heptanone, chloroform, dichlorobenzene, benzene, toluene, and ethyl-benzene. Only tentative identity was established for most of these components in control milk fat. Possible reaction mechanisms are presented for the formation of the compounds in irradiated milk fat. / Graduation date: 1966