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Food borne infections due to Salmonella enterica serovar Enteritidis (S. Enteritidis) has shown a dramatic increase in many countries. Different egg pasteurisation treaments have been developed in the past but are still not providing practical or optimal solutions. A method is required that ensure that eggs are microbiologically safe, that does not affect the functional quality and possibly also extend the egg shelf life. This research project formed part of a larger study, “Project 32438: The development of a novel microwave system for the pasteurisation of raw whole shell eggs” funded by the National Research Foundation Innovation Fund and conducted by a consortium consisting of the Council for Scientific and Industrial Research (CSIR), Delphius Technologies, Eggbert Eggs and University of Pretoria. One of the phases in the development of the microwave system was an evaluation of the effectiveness of applying different microwave power levels (250W and 300W) on eliminating or reducing S. Enteritidis as well as evaluating the effect on the functional properties of the eggs. The microbiological tests were conducted by the CSIR while the latter evaluation was the focus of the study reported here. Microwave pasteurised eggs had lower foaming capacity but higher Haugh values than control (unpasteurised) eggs. Albumin foam stability did not differ between control and microwave pasteurised eggs and the pH of the albumin was almost similar. The yolk pH of pasteurised eggs was higher than that of unpasteurised eggs. Significant differences were found for the sensory properties of broken out eggs as evaluated by a trained sensory panel. At 300W, pasteurised eggs collected from the left side of the oven had partially coagulated albumin that was not clear. The visual appearance of pasteurised eggs at 300W from left side was more adversely affected than the eggs collected from the right side oven position and all eggs pasteurised at 250W. The albumin foaming capacity, visual appearance and sensory properties of raw eggs pasteurised at 250W were slightly affected by microwave heating. A triangle taste test showed that there was a significant difference between control and pasteurised (300W) eggs. A home use consumer test showed that control and microwave pasteurised (250W) eggs were equally acceptable. Pasteurisation could extend the shelf life of whole shell eggs (WSE) by reducing or destroying spoilage microorganisms. Another phase of the project therefore focused on obtaining background data pertaining to the shelf life of eggs. The effect of coating of egg shells with mineral oil on the functional properties and shelf life of WSE stored at 16ºC (58 % RH); 25ºC during the day and 15ºC at night (55% RH) and 32ºC (32 % RH) for a period of six weeks, were evaluated. These conditions were selected to reflect typical temperatures that are used for storing eggs in South Africa. Haugh units of eggs decreased with storage time at all storage conditions but for coated eggs it decreased at a slower rate. The pH of both the yolk and albumin of coated shell eggs was lower than that of uncoated shell eggs. Coating did not have an influence on the foam stability of egg albumen. Foaming capacity of albumen was negatively affected by oil coating. Coated shell eggs stored at the three conditions had a prolonged shelf life compared to uncoated eggs stored in the same manner. If the prototype microwave oven can be optimised to ensure even distribution of microwaves, microwave pasteurisation of shell eggs has potential to become a significant break through in the poultry industry. / Dissertation (MInstAgrar)--University of Pretoria, 2007. / Food Science / unrestricted

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

<p>Large environmental, health, social and economical problems are connected with the use of</p><p>fossil fuels and, in a dominating part of the world, also the use of firewood. The goal for this</p><p>project was to develop and design an optimal solar oven system intended for food cooking</p><p>and water pasteurisation. Further the advantages and disadvantages, compared with other</p><p>energy resources were evaluated. Tests were carried out in Sweden as well as in Sri Lanka.</p><p>An extensive range of prototypes were tested and sifted out to a small number of designs that</p><p>were tested in Sri Lanka. A large number of evaluations and tests were carried out on many</p><p>different materials, among others tests were conducted according to the international standard</p><p>“Testing and Reporting Solar Cooker Performance ASAE S580 JAN03”.</p><p>The report shows a number of benefits compared to previous reports on the subject, for</p><p>example the development of indoor tests, the extensiveness and objectiveness of the tests, and</p><p>the fact that the report combines extensive practical test results with solid theoretical</p><p>background information.</p><p>The test resulted in two solar ovens with the same parabolic design but made out of different</p><p>materials. One oven is cheaper, simpler to produce and is considered for the target group poor</p><p>people in developing countries. This is made out of a corrugated cardboard that is covered</p><p>with aluminium foil. The second oven is more expensive but also more durable and is</p><p>intended for more wealthy people in the west that wants a good alternative to regular ways of</p><p>cooking food. It is made out of aluminium plate and mirrors.</p>

Large environmental, health, social and economical problems are connected with the use of fossil fuels and, in a dominating part of the world, also the use of firewood. The goal for this project was to develop and design an optimal solar oven system intended for food cooking and water pasteurisation. Further the advantages and disadvantages, compared with other energy resources were evaluated. Tests were carried out in Sweden as well as in Sri Lanka. An extensive range of prototypes were tested and sifted out to a small number of designs that were tested in Sri Lanka. A large number of evaluations and tests were carried out on many different materials, among others tests were conducted according to the international standard “Testing and Reporting Solar Cooker Performance ASAE S580 JAN03”. The report shows a number of benefits compared to previous reports on the subject, for example the development of indoor tests, the extensiveness and objectiveness of the tests, and the fact that the report combines extensive practical test results with solid theoretical background information. The test resulted in two solar ovens with the same parabolic design but made out of different materials. One oven is cheaper, simpler to produce and is considered for the target group poor people in developing countries. This is made out of a corrugated cardboard that is covered with aluminium foil. The second oven is more expensive but also more durable and is intended for more wealthy people in the west that wants a good alternative to regular ways of cooking food. It is made out of aluminium plate and mirrors.

In order to improve the water situation in rural areas of Bangladesh, a research group at the University of Dhaka has been developing low cost domestic methods to remove pathogens from surface water through pasteurisation using free solar energy. Pasteurisation is a process in which water is heated to approximately 60 °C and maintained for about 30 minutes to destroy pathogens. In these methods, the water is also exposed to UV-light from the sunshine, which causes destruction of diarrhoeal pathogens at temperatures somewhat lower than required in normal pasteurisation. However, despite many advantages these devices need to be installed for each time of use. Recently, a semi-permanent device has been developed which is expected to be more user friendly. The objective of this Master thesis has been to study and optimize the low cost semi-permanent device that can deliver safe drinking water to people in rural areas. Two test devices were constructed to determine the most effective treatment e.g. temperature, time, solar radiation, user-friendliness and cost. To replicate the results from the solar heating tests a model, based on the solar radiation and convective heat loss from the device, was used. The model was also able to determine the time duration at a certain solar radiation level to estimate when the water is safe to drink. The results revealed that the performance of the device depends on thickness of the insulation and thickness of the air gap. This is because the most important factors to achieve safe drinking water are solar radiation and time. The modelling indicated that the measured water temperature corresponds well with the calculated water temperature and also showed that the lowest required solar radiation is 390 W/m2 to reach drinking water criteria, at an air temperature of 25 °C. A study of microbiology showed that the semi-permanent low cost device could purify surface water to a safe level.

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)

Increasing consumer demand for new products with high nutritional qualities has spurred a search for new alternatives to food preservation. Pulsed electric field (PEF) is an emerging technology for non thermal food pasteurisation. Using this technology, enzymes, pathogenic and spoilage microorganisms can be inactivated without affecting the colour, flavour, and nutrients of the food. PEF treatment may be provided by applying pulsed electric field to a food product in a treatment zone between two electrodes at ambient , or slightly above ambient temperature. Exposure of microbial cells to the electric field induces a transmembrane potential in the cell membrane, which results in electroporation (the permeabilization of the membranes of cells and organelles) and/or electrofusion (the connection of two separate membranes into one) of the cells. An innovative pulsed electric field (PEF) unit was designed and constructed in the University of Auckland using modern IGBT technology. The system consists of main equipments, the high voltage pulse generator and the treatment chambers. The main focus of this work was to design an innovative PEF treatment chamber that provide uniform distribution of electric field, minimum increase in liquid temperature, minimum fouling of electrodes and an energy efficient system. Four multi pass treatment chambers were designed consisting of two stainless steel mesh electrodes in each chamber, with the treated fluid flowing through the openings of the mesh electrodes. The two electrodes are electrically isolated from each other by an insulator element designed to form a small orifice where most of the electric field is concentrated. Dielectric breakdown inside the chambers was prevented by removing the electrodes far from the narrow gap. The effect of the chambers different geometries on the PEF process in terms of electric parameters and microbial inactivation were investigated. Electric field intensity in the range of (17-43 kV/cm) was applied with square bipolar pulses of 1.7 µs duration. The effect of PEF treatment on the inactivation of gram-negative Escherichia coli ATCC 25922 suspended in simulated milk ultra-filtrate (SMUF) of 100%, 66.67% and 50% concentration was investigated. Treatments with the same electrical power input but higher electric field strengths provided larger degree of killing. The inactivation rate of E coli was significantly increased with increasing the electric field strength, treatment time and processing temperature. Morphological changes on E coli as a result of PEF treatment were studied under transmission electron microscopy (TEM). Significant morphological changes on E coli after PEF treatment were observed. The TEM studies suggested that the microbial inactivation was a consequence of electroporation and electrofusion mechanisms. Kinetic analysis of microbial inactivation due to PEF and thermal treatment of E coli suspended in SUMF were also studied. Comparison between measured (experimental) and predicted (theoretical) variation of E coli concentration with time following the PEF treatment was discussed, taking into consideration the recirculation mode of the PEF treatment. The treated liquid was circulated more than once through the treatment chamber to provide higher microbial inactivation. Arrhenius constants and activation energies of E coli inactivation using combined PEF and thermal treatment were calculated and generalized correlation for the inactivation rate constant as a function of electric field intensity and treatment temperature was developed. / Fonterra Research Institute (NZ) and the Foundation for Research Science and Technology (NZ)