High pressure (HP) kinetics of the microbial destruction and changes in the physicochemical characteristics of milk and pork were studied. Raw milk samples containing indigenous microflora of approximately 106 CFU/mL were heat sealed in dual peel sterilization pouches and subjected to HP treatment from 150--400 MPa with holding times ranging 5--120 min. The kinetic parameters (rate constant, k and decimal reduction time, D) for the microorganisms, alkaline phosphatase, color and viscosity were evaluated, based on first order kinetics and the pressure dependence of kinetic parameters was evaluated using pressure destruction time (PDT) and Arrhenius models. Kinetic data was well described by the first order model (R 2 > 0.90). / The application of pressure pulse was explored for pressure destruction of microorganisms as well as changes in physical-chemical characteristics of pork chops. Pork chops (2 days post-rigor) were subjected to HP treatment from 200--350 MPa for 0--120 min. Results showed that pressure changes of pork variables followed a dual effect consisting of an instantaneous pressure kill (IPK) with the application of pressure pulse (no holding) and a subsequent first order rate of destruction during the pressure hold time. The IPK values were pressure dependent and increased with pressure level. Parameters k and D indicated a higher rate of pressure destruction of microorganisms compared to quality attributes. / Kinetics of pressure destruction of Listeria monocytogenes Scott A were studied in relation to those of indigenous microorganism of milk and pork. The IPK was more pronounced with L. monocytogenes than with indigenous microflora. However, the kinetic parameters (k and D values) indicated a larger pressure resistance for L. monoctyogenes. HP processes were developed based on the standard plate count (SPC) kinetic data for indigenous microflora of milk as well as L. monocytogenes in milk and pork. The results showed that SPC kinetics permitted good estimation of microbial destruction in low pressure-lethality processes of milk and pork but its application at higher pressure-lethality levels were inaccurate. On the other hand, processes established based an destruction of L. monocytogenes were more predictable. Pressure pulse application to microbial lethality was also well predicted. / The shelf-life of milk and pork increased with the level of applied pressure lethality, but Q10 values suggested that low storage temperature was nevertheless required to control microbial growth and maintain quality. Storage of HP treated park offered some improvement in the texture but resulted in large color changes and drip losses. L. monocytogenes were not detected in any of the stored milk samples HP treated to achieve a lethality ≥10D.

The extent of denaturation and glycation of lysozyme and BSA with the application of high hydrostatic pressure (HHP) at 400 MPa at 30°C from 8 to 48 hours and focused microwave irradiation at 50°C under varying microwave power and from 10 to 60 minutes was investigated in the presence and absence of D-glucose. The HHP treatment caused 10 to 20% denaturation of lysozyme whereas microwave irradiation caused 20 to 40% denaturation, with more destruction to the lysozyme in the presence of glucose compared to the control. The extent of glycation was also higher with the high pressure samples, causing 60% glycation upon 8 hours of high pressure exposure, but decreasing to around 40% thereafter. Microwave irradiation brought about 40% glycation to the lysozyme samples upon 20 min of irradiation. BSA, on the other hand, was more susceptible to damage by high energy exposures. BSA samples were denatured to a greater extent compared to lysozyme, up to 80% upon the prolonged exposures, but in all treatments, glucose seemed to act as a protectant contrary to the case of lysozyme. The extent of glycation detected was also minimal, ranging from 8 to 20%. / The feasibility of analyzing glycated proteins using pyrolysis-GC/MS was also investigated. Taking advantage of the formation of a diagnostic marker---2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one---upon pyrolysis of glycated proteins, the intensity of this peak was used to correlate the extent of glycation. The intensity of this peak in the pyrograms of glycated lysozymes was found to increase linearly with increasing incubation times and subsequently with the sugar loads of the glycated lysozyme. In addition, using the pyrograms as unique fingerprints, the extent of structural changes between modified and unmodified proteins were also assessed.

High-pressure (HP) depresses the phase-transition point of water especially in the case of ice-I (down to -21°C at about 210 MPa). This phenomenon has several potential advantages in food processing applications, such as pressure shift freezing (PSF) and HP thawing. However, scientific knowledge available in this area is still relatively limited. The main objectives of this research were to investigate the phase-transition behavior of foods under pressure processing in the context of PSF and HP thawing techniques and to evaluate their impact on product quality. / Distilled water and fresh pork muscle were tested by a HP differential scanning calorimeter (DSC) using isothermal pressure scan (P-scan) and isobaric temperature scan (T-scan). P-scan tests showed that the phase-transition temperature (T) of pork was a function of the weighted-average pressure (P¯1--2): T = -1.17 - 0.102P¯1--2 - 0.00019 P&d1;21-2 (R2 = 0.99) that was much lower than that of pure ice. The phase-change latent heat of pork was estimated by P-scan. T-scan indicated the phase-transition point at a constant pressure, but it showed less accurate than P-scan. The ratio (Rice, %) of ice crystals formed by rapid release of pressure (P) was evaluated using the HP DSC: Rice-water = 0.115P + 0.00013P2 (R2 = 0.96) for water, and Rice-pork = 0.084P + 0.00012P2 (R2 = 0.95) for pork muscle. In the developed method, the pressure-dependent thermal properties of test materials are not required. / A preliminary study on ice-crystal formation was carried out using small gelatin gel samples frozen by conventional air freezing (CAF), liquid immersion freezing (LIF) and PSF at different pressures. The ovoid structure left from ice crystals was evaluated for area, equivalent diameter, roundness and elongation. The diameter (mean +/- S.D.) was 145 +/- 66, 84 +/- 26, 91 +/- 30, 73 +/- 29, and 44 +/- 16 mum for the treatments of CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. Roundness and elongation did not show a clear trend with different freezing tests. Similar experiments using small-size Atlantic salmon (Salmo salar) resulted in the diameter of 110 +/- 41, 17 +/- 8.4, 16 +/- 8.8, 8.2.5 and 5.0 +/- 2.1 mum for CAF, LIF and PSF at 100, 150 and 200 MPa, respectively. The roundness was 0.38 +/- 0.14, 0.55 +/- 0.21, 0.57 +/- 0.18, 0.63 +/- 0.14 and 0.71 +/- 0.14 for the above treatments, respectively. (Abstract shortened by UMI.)

Thesis (M.Eng.Sc.) - University of Queensland, 2004. / Includes bibliography.

Thesis (Ph. D)--University of Alabama at Birmingham, 2009. / Title from PDF t.p. (viewed June 30, 2010). Additional advisors: Viola L. Acoff, Krishan K. Chawla, Raymond J. Donahue, Gregg M. Janowski, Harry E. Littleton (ad hoc). Includes bibliographical references (p. 143-138).

Orientador: Paulo Roberto Ribeiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Instituto de Geociencias / Made available in DSpace on 2018-08-12T20:48:00Z (GMT). No. of bitstreams: 1 Atolini_TarcilaMantovan_M.pdf: 2488021 bytes, checksum: c3cbe83ac1e08cbfdb561f27e085ffcc (MD5) Previous issue date: 2008 / Resumo: Um dos avanços referentes ao desenvolvimento de tecnologias para perfuração de poços em condições severas de pressão e temperatura está ligado aos fluidos de perfuração. O entendimento do comportamento da mistura de fluido de perfuração e gás da formação, numa situação de influxo de gás da formação para o poço (kick), é essencial para as operações de controle de poço. Especialmente quando se utilizam fluidos orgânicos, os quais dificultam a detecção do influxo. O principal objetivo do presente trabalho é o estudo do comportamento termodinâmico desses fluidos a condições compatíveis com as de fundo de poços de alta temperatura e alta pressão (ATAP). Para atingir esta meta utilizou-se uma célula PVT com limite operacional de 200°C e 100MPa. Primeiramente estudou-se o sistema metano/nparafina nas composições de 0 a 95% em fração molar de metano e nas temperaturas de 70°C a 130°C. Numa segunda fase do trabalho foi estudado o sistema metano/emulsão com duas composições de emulsões, uma 60% n-parafina e outra 70%, variando-se também fração de gás e temperatura. Através dos dados experimentais do sistema metano/n-parafina realizou-se modelagem computacional para o cálculo da solubilidade, densidade e fator volume de formação, obtendo-se correlações que permitiram avaliar projeções baseadas na hipótese da aditividade. Para o cálculo direto dessas propriedades obtiveram-se correlações para o sistema metano/emulsões, as quais foram empregadas em cálculos de volume ganho no tanque como exemplo de sua aplicabilidade / Abstract: One of the advances in the development of drilling technologies under severe conditions of pressure and temperature is related to the drilling fluids. The understanding of the behavior of drilling fluid and the formation gas mixture, in a kick situation, is essential for the well control operations. Especially when organic fluids are used, which makes it more difficult to detect the influx of gas from the formation into the well. The main objective of this work was the study of the PVT behavior of these fluids at pressures and temperatures consistent with the HTHP well conditions. In order to accomplish that, a PVT cell with an operational limit of 200°C and 100MPa was used. First the system methane/n-paraffin was studied, with compositions from 0 to 95% in molar fraction of methane and at temperatures from 70 to 130°C. In a second phase of this work the system methane/emulsion was studied, for two different emulsions, one with 60% n-paraffin and another with 70%, also varying gas fraction and temperature. Through the experimental data of the methane/n-paraffin system a computational modeling was conducted to calculate solubility, density and formation volume factor, resulting in correlations that enabled the evaluation of the validity of the additivity hypothesis. For the entire experimental parameters spam, mathematical adjustments of the methane/emulsion system were done. This correlations were used in pit gain calculations as an example of its applicability / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Orientador: Marcelo Cristianini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T11:43:23Z (GMT). No. of bitstreams: 1 Dosualdo_GustavoLevy_M.pdf: 869899 bytes, checksum: 1f530194417d892a2ca5e4bde3aa7461 (MD5) Previous issue date: 2007 / Resumo: Diferentes tratamentos não térmicos têm sido estudados nos últimos anos como métodos substitutos ou complementares dos tradicionais tratamentos térmicos na conservação de alimentos. Estes tratamentos apresentam a vantagem de não causar alterações indesejáveis no sabor dos produtos ou perdas de nutrientes. Dentre os tratamentos não térmicos, um dos mais estudados é o processamento a alta pressão, que pode ser aplicado através de dois métodos: o isostático e o de homogeneização. O método isostático têm sido estudado com maior freqüência, no entanto, o método de homogeneização apresenta a vantagem de proporcionar uma produção contínua. Este trabalho visou avaliar o tratamento de homogeneização de alta pressão aplicado à água de coco para eliminação da atividade enzimática e de possíveis contaminações microbiológicas do produto. Os processamentos de Homogeneização a Ultra Alta Pressão (HUAP) foram realizados no equipamento nG7400H:320, fabricado pela Stansted Fluid Power (Stansted, Inglaterra), que atinge pressões de até 320 MPa. Estudou-se a influência da pressão de processo e do pH do produto nas atividades enzimáticas de peroxidase e polifenoloxidase e na destruição da bactéria Lactobacillus fructivorans e da levedura Saccaromyces cerevisiae. Os tratamentos realizados não causaram inativação satisfatória das enzimas presentes na água de coco, porém há evidências de que o tratamento pode ser eficaz se for efetuado em pressões mais elevadas. De maneira geral, a peroxidase apresentou maior resistência ao tratamento do que a polifenoloxidase. A realização de três tratamentos seqüenciais a 300 MPa causou redução parcial da atividade das enzimas, embora não tenha sido verificada uma potencialização do efeito dos tratamentos HUAP quando realizados seqüencialmente. O tratamento mostrou-se eficaz na eliminação de contaminação microbiológica do produto. Para o Lactobacillus fructivorans, a aplicação de tratamentos em pressões maiores que 250 MPa eliminou totalmente a carga de microrganismos inoculada no produto, de 2,0 x 107 UFC/mL. O pH do produto exerceu uma influência muito menor na eliminação dos microrganismos do que a pressão de processo. Em altas pressões (próximas a 300 MPa), o processamento mostrou-se mais efetivo na destruição do Lactobacillus fructivorans quando utilizado em produtos com pH mais elevado. Para baixas pressões, o efeito foi inverso, ou seja, tratamentos em produtos com pHs mais ácidos causaram maior inativação. Para as leveduras (Saccaromyces cerevisiae), a aplicação de tratamentos a pressões acima de 200 MPa eliminou totalmente a carga microbiana inoculada na água de coco, que era de 4,4 x 105 UFC/mL. O estudo da influência do pH não apresentou resultados conclusivos porque a maioria dos tratamentos realizados nesta parte do estudo eliminou todas as células de microrganismos presentes no produto, o que dificultou a análise dos dados. Observou-se uma tendência de que valores menores do pH do produto possam favorecer a eliminação das células das leveduras durante o processamento Nas condições estudadas pode-se concluir que o tratamento de homogeneização a alta pressão foi eficiente na eliminação dos microrganismos estudados mas não foi eficiente para causar a inativação das enzimas presentes no produto (peroxidase e polifenoloxidase). Com isto, espera-se que a água de coco tratada pelo método HUAP apresente boa estabilidade microbiológica, mas não apresente boa estabilidade química, ficando sujeita a alterações devido a reações catalisadas por estas enzimas / Abstract: Different not thermal treatments have been studied in the last years as substitute or complementary methods of the traditional thermal treatments in the food conservation. These treatments present the advantage not to cause alterations undesirable in the flavor of the products or losses of nutrients. Amongst the not thermal treatments, one of the most studied is the processing the high pressure, that can be applied through two methods: the isostático and of homogenization. The isostático method has been studied more frequently, however, the homogenization method presents the advantage to provide a continuous production. This work aimed at to evaluate the applied treatment of high-pressure homogenization to the water of coconut for elimination of the enzymatic activity and of possible microbiological contaminations of the product. The processings of Homogenization Ultra Alta Pressão (HUAP) had been carried through in the equipment nG7400H:320, manufactured for the Stansted Fluid Power (Stansted, England), that it reaches pressures of up to 320 MPa. Studied it influence of the pressure of process and pH of the product in the enzymatic activities of peroxidase and polifenoloxidase and in the destruction of the Lactobacillus bacterium fructivorans and the Saccaromyces leavening cerevisiae. The carried through treatments had not caused satisfactory inativação das enzymes gifts na coconut water, however it has evidences of that the treatment can be efficient will have been effected in raised pressures more. In general way, peroxidase presented greater resistance to the treatment of that polifenoloxidase. The accomplishment of three sequential treatments the 300 MPa caused partial reduction of the activity of enzymes, has even so not been verified a potencialização of the effect of treatments HUAP when carried through sequentially. The treatment revealed efficient in the elimination of microbiological contamination of the product. For the Lactobacillus fructivorans, the application of treatments in 250 bigger pressures that MPa total eliminated the load of microrganismos inoculated in the product, of 2,0 x 107 UFC/mL. PH of the product very exerted a lesser influence in the elimination of the microrganismos of that the process pressure. In high pressures (next the 300 MPa), the processing more revealed more effective in the destruction of the Lactobacillus fructivorans when used in products with pH raised. For low pressures, the effect was inverse, or either, treatments in more acid products with pHs had caused greater inativação. For the leavenings (Saccaromyces cerevisiae), the application of treatments the 200 pressures above of MPa total eliminated the inoculated microbiana load in the coconut water, that was of 4,4 x 105 UFC/mL. The study of the influence of pH it did not present resulted conclusive because the majority of the treatments carried through in this part of the study eliminated all the cells of microrganismos gifts in the product, what it made it difficult the analysis of the data. A trend was observed of that lesser values of pH of the product can favor the elimination of the cells of the leavenings during the processing In the studied conditions can be concluded that the treatment of homogenization the high pressure was efficient in the elimination of the studied microrganismos but it was not efficient to cause the inativação of enzymes gifts in the product (peroxidase and polifenoloxidase). With this, one expects that the water of coconut treated for method HUAP presents good microbiological stability, but does not present good chemical stability, being subjects the alterations due the reactions catalyzed for these enzymes / Mestrado / Mestre em Tecnologia de Alimentos

D.Ing. / The research described in this thesis is an investigation into fundamental aspects of the mechanical excavation of hard rock using free rolling cutters, currently being undertaken at the Chamber of Mines of South Africa Research Organization. The motivation for undertaking this study was provided by the need to improve the effectiveness and operational efficiency of this type of tool with regards to its application in the South African gold mining industry. Earlier work has shown that the use of high-pressure water jets enhances the performance of mechanical cutting in hard rock. To assess the potential of this approach for use in conjunction with free rolling cutters, a series of laboratory tests was conducted using both disc and button type cutters, to determine the relative effects, on cutter performance, of variations in the relevant jet and cutting parameters. The parameters investigated were jet pressure, jet configuration, depth and spacing of cuts and cutting speed. Jets of diameter 1,2 mm were used singly and in combination of 2 and 4 jets at pressures in the range of 5 MPa to 40 MPa which gave flow rates of up to 0,3 lis per jet. Cut spacing, cut depth and cutting speed were varied between 15 mm and 90 mm, 2 mm and 6 mm, and 0,1 mls and 1,0 mls respectively. Tests were carried out on a linear rock cutting machine, purpose built according to specifications prepared from measurements made during underground field trials, which gave it the ability to test full-scale cutters under loading conditions representative of those found in the field. All the tests carried out were performed in the constant penetration, multiple pass (groove deepening) cutting mode, using dressed (smooth) and pre-conditioned (pre-roughened) rock surfaces.

No description available.

No description available.