<p>In recent years, numerous multistate foodborne outbreaks have been reported that are often associated with low moisture foods (LMFs). The survival of microorganisms in low moisture conditions has become one of the major concerns in the food industry. With the increasing number of recalls, it is necessary to ensure food safety by developing and validating the process parameters. Establishing a thermal process requires a detailed understanding of the inactivation kinetics of the target pathogen with respect to both the process (temperature, time, equipment) and the product conditions (water activity, composition). Along with the most widely used conventional thermal processing, there has been an increase in the demand for natural or minimally processed foods. As a result, many alternative non-thermal processing approaches that provide antimicrobial benefits while retaining the quality attributes of the food product are under investigation. This research focused on studying the inactivation kinetics of foodborne pathogens <em>Salmonella enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em> in powdered LMFs using both the thermal and non-thermal (cold plasma) processing technologies. The efficacy of a dielectric barrier discharge cold plasma equipment was tested against pathogens <em>Salmonella</em> <em>enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em> in LMFs at 70 kV, resulting in 3.8 log reduction in <em>Cronobacter</em>, and 4.41 log reduction in <em>Salmonella</em> after 5 min of cold plasma treatment in pea protein. The cellular damage to the pathogens was examined by transmission electron microscopy (TEM), and the reactive oxygen (ROS: OH, O) and nitrogen (RNS: N₂, N₂⁺) species were identified using optical emission spectroscopy. The RMSE for the model was found to be between 0.11 and 0.36 with the low standard error of the parameters (δ, n, and log N₀), which illustrated that the Weibull model was a good fit for the experimental inactivation data. </p> <p>In the thermal processing study, the inactivation kinetic parameters of these pathogens were estimated at 70, 80, and 90 °C at 0.11, 0.22, and 0.33 water activity in pea protein powder. The non-isothermal temperature profiles were simulated by building a two dimensional, axisymmetric heat transfer model of the test cell. The inactivation parameters D_ref, z_T, and z_aw were estimated in MATLAB by using a one-step non-linear regression analysis, which was a combination of the primary log-linear model with the secondary modified-Bigelow model. The model was found to be a good fit, showing lower root mean square error (RMSE) and residuals. Further, <em>Enterococcus</em> <em>faecium</em> was observed to have higher D-values at all the processing temperatures and water activity levels as compared to <em>Salmonella enteritidis</em> PT30 and <em>Cronobacter</em> <em>sakazakii</em>, which provides valuable evidence that <em>Enterococcus</em> <em>faecium</em> can be used as a surrogate microorganism for validating the thermal process for pea protein powder.</p>

Resíduos de Serviços de Saúde (RSS), ainda que tratados e dispostos em aterros sanitários, podem ser causas de impactos ambientais por apresentarem algum indicador de periculosidade. Segundo o apêndice IV da Resolução da Agência Nacional de Vigilância Sanitária (Anvisa) RDC nº 306/2004, para as tecnologias de tratamento desses resíduos é necessário que se atinja pelo menos o Nível III de inativação microbiana. Perante a ausência de dados na literatura que revelassem o tempo de exposição, temperatura e pressão ideais para a inativação microbiana no tratamento de RSS por autoclavagem e se a fração ocupada dos resíduos na autoclave poderia interferir na eficiência da desinfecção definiu-se o objetivo do trabalho para otimização do processo. Para os testes foram utilizados endósporos de Geobacillus stearothermophilus como bioindicadores e instalados cinco termopares na autoclave para aferição da temperatura dentro de todo o espaço da câmara. O RSS foi sintetizado diante das caracterizações como composição gravimétrica, distribuição granulométrica, densidade específica aparente, massa específica aparente e teor de umidade. Apresentou-se uma proposta metodológica para a avaliação do tratamento de RSS frente às dificuldades encontradas. Realizou-se ensaios com 116ºC, 125ºC e 134ºC, observando a fração de inativação em seis tempos de exposição diferentes. Sabendo-se que é padronizada em estabelecimentos de saúde a temperatura ideal para esterilização de materiais de 121ºC, apesar de não terem sido encontrados trabalhos científicos que comprovem a eficiência da esterilização nessa circunstância, foram realizados testes a 50 e 60 minutos de exposição para avaliar essa condição. Inoculou-se 106 endósporos nas amostras e a recuperação foi feita com filtração após a lavagem dos resíduos, sendo realizada a técnica de pour plate para contagem das unidades formadoras de colônias (UFC). O mesmo procedimento foi feito com a amostra retirada da autoclave. A fração de inativação dos endósporos atingiu 100% no tempo de 30 minutos de exposição à temperatura máxima de 134ºC e pressão absoluta de 2,3 kgf/cm2, resultado obtido através da relação do número de micro-organismos recuperados considerados como inoculados e o número de micro-organismos sobreviventes ao tratamento. A 121ºC houve recuperação de UFC após tratamento. A fração de ocupação não foi um fator delimitante para a inativação de endósporos, pois a temperatura se manteve a mesma independentemente da quantidade de resíduo submetido à autoclavagem. Um outro objetivo era avaliar experimentalmente a reprodução dos micro-organismos frente às condições operacionais de autoclavagem e do tempo de permanência do rejeito em condições ambientais. Esse estudo comprovou que a inativação nessas condições otimizadas esteriliza o resíduo, sendo que nenhum micro-organismo voltou a se reproduzir após dias expostos em temperatura ambiente, ou seja, não haveria riscos de contaminação em aterro sanitário quando depositados os rejeitos. Ter encontrado essas condições ideais e avaliado o processo de autoclavagem pode significar um grande avanço nas próprias unidades de tratamento, que terão um parâmetro estabelecido para trabalho. / Healthcare waste, even when treated and disposed of in landfills, can be causes of environmental impacts because they present some hazard indicator. According to appendix IV of Resolution of the National Health Surveillance Agency of Brazil (Anvisa) RDC nº 306/2004, for technologies of healthcare waste treatment, it is necessary to achieve at least Level III of microbial inactivation. The purpose of this research to optimize the process was defined taking into account the absence of data in the literature that revealed the optimal exposure time, temperature and pressure for microbial inactivation through the healthcare treatment by autoclaving and whether the fraction occupied by waste in the autoclave could interfere with the effectiveness of the disinfection. For the tests, endospores of Geobacillus stearothermophilus were used as bioindicators and five thermocouples were installed in the autoclave for temperature measurement throughout the chamber space. The healthcare waste was synthesized by characterizations such as gravimetric composition, granulometric distribution, apparent specific density, apparent specific mass and moisture content. A methodological proposal for the evaluation of waste treatment was introduced taking into consideration the difficulties encountered. Tests were performed at 116ºC, 125ºC and 134ºC, observing the fraction of inactivation at six different exposure times. Since the sterilization of materials at 121ºC is standardized in health establishments, even though no scientific studies were found to prove the sterilization efficiency in these conditions, tests were performed at 50 and 60 minutes of exposure to evaluate this condition. The concentration of 106 endospores were inoculated in the samples and the recovery was done with filtration after washing the waste, and the \"pour plate\" technique was used to count the colony forming units. The same procedure was done with the sample removed from the autoclave. The inactivation fraction of the endospores reached 100% in the time of 30 minutes of exposure to the maximum temperature of 134ºC and absolute pressure of 2.3 kgf/cm2, a result obtained by the ratio of the number of recovered microorganisms considered as inoculated and the number of microorganisms surviving the treatment. At 121ºC there was recovery of colony forming units after treatment. The occupation fraction was not a limiting factor for the inactivation of endospores, since the temperature remained the same regardless of the amount of waste submitted to autoclaving. Another objective was to experimentally evaluate the reproduction of the microorganisms taking into consideration the operational conditions of autoclaving and the amount of time that the waste remains under environmental conditions. This study proved that the inactivation under these optimized conditions sterilizes the waste, and that no microorganism would reproduce again after days exposed at room temperature, therefore, there would be no risk of contamination in a landfill when the waste is deposited. Having found these ideal conditions and evaluated the autoclaving process can mean a major advance in the treatment units themselves, which will have an established parameter for work.

<p>Multiple studies have demonstrated atmospheric cold plasma (ACP) as an effective non-thermal technology for microbial decontamination, surface modification, and functionality alteration in food processing and packaging. ACP constitutes charged particles, such as positive and negative ions, electrons, quanta of electromagnetic radiation, and excited and non-excited molecules, which corresponds to its predominant reactive properties. However, in many of these applications, the interactions between plasma and the components in food matrix are not well-understood. The <b>overall goals</b> of this dissertation were to 1) evaluate the interactions between high voltage atmospheric cold plasma (HVACP) and microbes in liquid and semi-solid food; 2) investigate plasma transfer into semi-solid foods and determine the relationship between microbial inactivation and plasma transfer; 3) explore the interactions between plasma and proteins. </p> <p>The first study explored the microbial (<i>Salmonella</i> <i>enterica</i> serovar Typhimurium, <i>S</i>. <i>enterica</i>) inactivation efficacy of HVACP. The physicochemical interactions between HVACP and biomolecules, including an enzyme (pectin methylesterase, PME), vitamin C and other components in orange juice (OJ) under different conditions was also evaluated. Both direct and indirect HVACP treatment of 25 mL OJ induced greater than a 5 log reduction in <i>S</i>. <i>enterica</i> following 30 s of treatment with air and MA65 gas with no storage. For 50 mL OJ, 120 s of direct HVACP treatment followed by 24 h storage achieved <i>S</i>. <i>enterica</i> reductions of 2.9 log in air and 4.7 log in MA65 gas. An indirect HVACP treatment of 120 s followed by 24 hours storage resulted in a 2.2 log reduction in air and a 3.8 log reduction in MA65. No significant (<i>P </i>< 0.05) Brix or pH change occurred following 120 s HVACP treatment. HVACP direct treatment reduced vitamin C content by 56% in air and PME activity by 74% in air and 82% in MA65. These results demonstrated that HVACP can significantly reduce <i>Salmonella</i> in OJ with minimal quality degradation.</p> <p>The second study in this dissertation examined the penetration process of plasma into semi-solid food and the resulting microbial inactivation efficacy. Agar gels of various densities (0.25, 0.5, 1.0, and 2%) with a pH indicator were inoculated with <i>S</i>. <i>enterica</i> (10⁷>CFU) and exposed directly (between the electrode) or indirectly (adjacent to the plasma field created between the two electrodes) to 90 kV at 60 Hz for up to 1.5 h. A long treatment time (1.5 h) caused sample temperature to increase 5~10 °C. The microbial analysis indicated a greater than 6 log₁₀ (CFU) reduction (both with air and MA65) in the zone with a pH change. Inactivation of bioluminescence cells in the plasma penetrated zone confirmed that the plasma, and its generated reactive species, inactivate microbial as it penetrates into the gel. A two-minute HVACP direct treatment with air at 90 kV induced greater than 5 log₁₀ (CFU)<i> S</i>. <i>enterica </i>reduction in applesauce. <em></em></p> <p>The third study investigated the interactions between HVACP and protein, using bovine serum albumin (BSA) as a model protein. The physicochemical and structural alteration of BSA and its reaction mechanism, when subjected to HVACP, were investigated. After treating 10 mL of BSA solution (50 mg/mL) at 90 kV for 20, 40, or 60 min, we characterized structural alteration and side-group modification. FTIR spectroscopy, Raman spectroscopy, and circular dichroism analysis indicated protein unfolding and decreased secondary structure (25 % loss of α-helix, 12% loss of β-sheet) in HVACP treated BSA. Average particle size in the protein solutions increased from 10 nm to 113 µm, with a broader distribution after 60 min HVACP treatment indicating protein aggregation. SDS-PAGE and mass spectrometer analysis observed a formation of new peptides of 1 to 10 kDa, indicating that the plasma triggered peptide bond cleavage. Chemical analysis and mass spectrometer results confirmed the plasma modifications on the side chains of amino acids. This study reveals that HVACP treatment may effectively introduce structural alteration, protein aggregation, peptide cleavage, and side-group modification to proteins in aqueous conditions, through several physicochemical interactions between plasma reactive species (reactive oxygen species and reactive nitrogen species) and the proteins. This finding can be readily applied to other plasma-protein studies or applications in the food system, such as enzyme inactivation or protein-based film modifications.</p>

In this study the action of high hydrostatic pressure (HHP) on compression heating of liquid foods and pressure transmitting fluids, inactivation of Escherichia coli and Listeria innocua in different food media (milk and fruit juices), pulsed pressure and high pressure carbon dioxide treatments was investigated. The experimental results in this study allowed pointing out some important results: (i) The thermal effects of compression should be taken into account when HHP pasteurization processes are developed. Initial temperature of the food product and compression rate should carefully be selected in order to compensate the compression heating / (ii) The HHP inactivation kinetics need not follow traditional first-order kinetics, hence alternative inactivation models are ought to be found. Weibull model can be used for HHP inactivation kinetics of microorganisms / (iii) The pulsed pressure treatment could be an alternative to continuous HHP, but optimization should be done between the pulse holding time, the number of pulses and the pressure level to reach the desirable number of log-reduction of microorganisms (E. coli and L. innocua) compatible with an industrial application / (iv) The storage duration and storage temperature after HHP treatment should carefully be optimized to increase the safety of HHP treated fruit juices since the growth of injured microorganisms can be avoided during storage / (v) The high pressure carbon dioxide (HPCD) treatment in combination with pulsed pressure can be an efficient way to inactivate the microorganisms in skim milk and to reduce the maximum pressure level for the desired log-reduction.

The application of non-thermal processes pulsed electric fields (PEF) and cross-flow micro-filtration (CFMF) continuous to be studied with the purpose of controlling microorganisms in milk. Trends suggesting increased adoption include the study of Food Safety Objectives as a safety criterion, the promotion of sustainable processing, and the implementation of hurdle strategies. While the advance of gentle processing is counteracted by the risk of enhanced resistance due to microbial stress response, several techniques can be applied to quantitatively assess its impact. The objective of this project was to evaluate the effectiveness of microbial inactivation by PEF and CFMF at various steps of milk processing including shelf-life, its comparison with high temperature short time (HTST) pasteurization, and the quantitative assessment of the cross protection resistance to PEF of Escherichia coli O157:H7. Some differences in mesophilics inactivation were observed in milks (fat contents between 1.1% and 3.1%). Increasing the PEF inlet temperature decreased the treatment time by three or two-fold. The combination of CFMF/PEF yielded similar microbial reductions as CFMF/HTST. Higher inactivation of the coliforms was achieved in homogenized cream (12% fat) compared to non-homogenized. The linear relation between electrical conductivity and nutrient content (fat and solids content) was established. In a parallel study the PEF/CFMF sequence resulted in higher inactivation of mesophilics compared to CFMF/PEF and HTST. The shelf life was acceptable for CFMF/PEF and HTST after 7 days, while enterics and psychrotrophs grew more after PEF/CFMF, thermodurics did after HTST. The growth and stress of Escherichia coli O157:H7 in lactose containing broths was monitored by absorbance and fluorescence expression of stress reporters. Growth was explained using a secondary model, and stress response using mechanistic and probabilistic models. PEF inactivation was evaluated following the Weibull distribution after the cells reached stationary phase or maximum fluorescence expression. Similar resistances were observed within the cells grown in lactose broth at 10, 25 or 40°C, as within stressed cells (starved or cold shocked). Cells grown at 45 °C were more resistant compared to the cells grown in acid, high salt concentration while the ones grown at cold temperatures were the weakest. / Dairy Farmers of Ontario, Natural Sciences and Engineering Research Council.

Resíduos de Serviços de Saúde (RSS), ainda que tratados e dispostos em aterros sanitários, podem ser causas de impactos ambientais por apresentarem algum indicador de periculosidade. Segundo o apêndice IV da Resolução da Agência Nacional de Vigilância Sanitária (Anvisa) RDC nº 306/2004, para as tecnologias de tratamento desses resíduos é necessário que se atinja pelo menos o Nível III de inativação microbiana. Perante a ausência de dados na literatura que revelassem o tempo de exposição, temperatura e pressão ideais para a inativação microbiana no tratamento de RSS por autoclavagem e se a fração ocupada dos resíduos na autoclave poderia interferir na eficiência da desinfecção definiu-se o objetivo do trabalho para otimização do processo. Para os testes foram utilizados endósporos de Geobacillus stearothermophilus como bioindicadores e instalados cinco termopares na autoclave para aferição da temperatura dentro de todo o espaço da câmara. O RSS foi sintetizado diante das caracterizações como composição gravimétrica, distribuição granulométrica, densidade específica aparente, massa específica aparente e teor de umidade. Apresentou-se uma proposta metodológica para a avaliação do tratamento de RSS frente às dificuldades encontradas. Realizou-se ensaios com 116ºC, 125ºC e 134ºC, observando a fração de inativação em seis tempos de exposição diferentes. Sabendo-se que é padronizada em estabelecimentos de saúde a temperatura ideal para esterilização de materiais de 121ºC, apesar de não terem sido encontrados trabalhos científicos que comprovem a eficiência da esterilização nessa circunstância, foram realizados testes a 50 e 60 minutos de exposição para avaliar essa condição. Inoculou-se 106 endósporos nas amostras e a recuperação foi feita com filtração após a lavagem dos resíduos, sendo realizada a técnica de pour plate para contagem das unidades formadoras de colônias (UFC). O mesmo procedimento foi feito com a amostra retirada da autoclave. A fração de inativação dos endósporos atingiu 100% no tempo de 30 minutos de exposição à temperatura máxima de 134ºC e pressão absoluta de 2,3 kgf/cm2, resultado obtido através da relação do número de micro-organismos recuperados considerados como inoculados e o número de micro-organismos sobreviventes ao tratamento. A 121ºC houve recuperação de UFC após tratamento. A fração de ocupação não foi um fator delimitante para a inativação de endósporos, pois a temperatura se manteve a mesma independentemente da quantidade de resíduo submetido à autoclavagem. Um outro objetivo era avaliar experimentalmente a reprodução dos micro-organismos frente às condições operacionais de autoclavagem e do tempo de permanência do rejeito em condições ambientais. Esse estudo comprovou que a inativação nessas condições otimizadas esteriliza o resíduo, sendo que nenhum micro-organismo voltou a se reproduzir após dias expostos em temperatura ambiente, ou seja, não haveria riscos de contaminação em aterro sanitário quando depositados os rejeitos. Ter encontrado essas condições ideais e avaliado o processo de autoclavagem pode significar um grande avanço nas próprias unidades de tratamento, que terão um parâmetro estabelecido para trabalho. / Healthcare waste, even when treated and disposed of in landfills, can be causes of environmental impacts because they present some hazard indicator. According to appendix IV of Resolution of the National Health Surveillance Agency of Brazil (Anvisa) RDC nº 306/2004, for technologies of healthcare waste treatment, it is necessary to achieve at least Level III of microbial inactivation. The purpose of this research to optimize the process was defined taking into account the absence of data in the literature that revealed the optimal exposure time, temperature and pressure for microbial inactivation through the healthcare treatment by autoclaving and whether the fraction occupied by waste in the autoclave could interfere with the effectiveness of the disinfection. For the tests, endospores of Geobacillus stearothermophilus were used as bioindicators and five thermocouples were installed in the autoclave for temperature measurement throughout the chamber space. The healthcare waste was synthesized by characterizations such as gravimetric composition, granulometric distribution, apparent specific density, apparent specific mass and moisture content. A methodological proposal for the evaluation of waste treatment was introduced taking into consideration the difficulties encountered. Tests were performed at 116ºC, 125ºC and 134ºC, observing the fraction of inactivation at six different exposure times. Since the sterilization of materials at 121ºC is standardized in health establishments, even though no scientific studies were found to prove the sterilization efficiency in these conditions, tests were performed at 50 and 60 minutes of exposure to evaluate this condition. The concentration of 106 endospores were inoculated in the samples and the recovery was done with filtration after washing the waste, and the \"pour plate\" technique was used to count the colony forming units. The same procedure was done with the sample removed from the autoclave. The inactivation fraction of the endospores reached 100% in the time of 30 minutes of exposure to the maximum temperature of 134ºC and absolute pressure of 2.3 kgf/cm2, a result obtained by the ratio of the number of recovered microorganisms considered as inoculated and the number of microorganisms surviving the treatment. At 121ºC there was recovery of colony forming units after treatment. The occupation fraction was not a limiting factor for the inactivation of endospores, since the temperature remained the same regardless of the amount of waste submitted to autoclaving. Another objective was to experimentally evaluate the reproduction of the microorganisms taking into consideration the operational conditions of autoclaving and the amount of time that the waste remains under environmental conditions. This study proved that the inactivation under these optimized conditions sterilizes the waste, and that no microorganism would reproduce again after days exposed at room temperature, therefore, there would be no risk of contamination in a landfill when the waste is deposited. Having found these ideal conditions and evaluated the autoclaving process can mean a major advance in the treatment units themselves, which will have an established parameter for work.

No description available.