The initial aim of this work was to evaluate processing conditions for extended shelf life (ESL) milk to have a shelf life at refrigeration temperature of 60 d. Milk was processed on a pilot-scale ultra-high-temperature processing plant and evaluated for microbial and sensory quality over 60 d at 7°C storage. Results of this study showed that lower process temperatures were preferable to minimize cooked flavors and that the minimum safe processing temperature was 134°C for 4 s as determined by the destruction of bacterial spores in the processed milk. Consumer preference panel results indicated that consumers preferred milk processed at 134°C for 4 s (those recommended in this study for ESL processing) to commercial UHT milk although there was a slight preference for pasteurized milk. The critical sensory characteristic of the processed milk was a cooked flavor, which decreased with lower processing temperature and shorter storage time; however, a significant increase in flavors that could be associated with lipolytic activity was also noted. This study highlighted deficiencies in existing methods for determining heat-stable bacterial products in thermal-processed foods. No rapid, sensitive assay for detection of heat-stable spores or lipases in milk exists. If such assays were available, it would allow processors to determine Lipase activity and bacterial spore counts before processing and direct raw milk with low spore counts and low lipolytic activity into long-shelf-life products. To this end, assays to rapidly quantitate spores and lipolytic activity in milk were developed. The lipase assay relies on the hydrolysis of p-nitrophenyl caprylate liberating a yellow color that is detected using reflectance colorimetry. The assay is sensitive to 5 mUnits/ml and is linearly correlated to spectrophotometry (r2 = 0.93) and release of titratable free fatty acids (r2 = 0.92 to 0.97). An immunocapture, enzyme-linked immunoassay coupled with a fluorescent detection system was developed for and resulted in a prototype spore assay using Bacillus stearothermophilus spores. This organism was selected because it is extremely heat resistant, is commonly found in milk, and is associated with spoilage of milk and milk products. The assay was able to quantitate spores down to 103 cfu/ml in milk and other products in about 1.5 h. Other detection limits could be set if needed.

A series of experiments were devised in order to establish the relationship between fibre addition to an extruded breakfast cereal base recipe and the physical, chemical and nutritional qualities of the breakfast cereals. A twin screw extruder was used for all experiments. Preliminary investigations using, guar gum and inulin additions, illustrated that screw configuration was important in determining the physical properties (degree of expansion, firmness and crunchiness) of the extruded products. Thus a screw configuration featuring a reverse screw and mixing zone within the barrel was selected for the larger research study. In the extended experimental design guar gum, inulin, wheat bran, swede fibre, and hi-maize were added to a base recipe at; 5, 10 and 15 % of total dry ingredient content. A further experiment was completed to investigate the synergistic effects of adding differing fibres in combination. Results illustrated that soluble dietary fibres (for instance guar and inulin) created a porous, less firm, but crispier breakfast cereals than the insoluble fibres, which generally produced denser, harder products. The inclusion of fibre into the extruded breakfast cereals did not affect the chemical composition of the breakfast cereal significantly (P=0.05) when taking into account the diluting factor of adding the fibre into the base recipe. However moisture loss / retention on extrusion varied significantly (P=0.05) between fibre combinations. Thus the moisture loss of samples containing guar or inulin were greater than those samples containing wheat bran and swede fibre. The process of extrusion did not significantly effect the amount of protein, starch or fibre in the samples when the extruded samples were compared to the control samples. Pasting properties of samples were evaluated using the Rapid Visco Analyser. This was conducted to try to determine associations between starch pasting properties (gelatinisation events) of the raw and extruded samples and the physical or nutritional quality of the products. However, the results did not show clear associations. An in vitro analysis was conducted to determine the effect of fibre addition on starch breakdown and subsequent release of reducing sugars. Breakfast cereals which included wheat bran, guar and swede fibre all showed a reduced rate of starch degradation compared to the control (P=0.05). These fibres appeared to inhibit the rate of enzyme degradation of starch, in effect increasing the amount of slowly digestible starch in the breakfast cereals. Cereal samples containing inulin did not show this pattern. Generally the rate of inhibition was related to the amount of fibre added to the base recipe. When used in combinations, samples containing inulin and hi-maize were not significantly different to the control in terms of reducing sugar release, whereas inclusion of guar gum significantly reduced this release. In conclusion, the addition of selected fibres can be used effectively as a method of manipulating the starch degradation rates of extruded breakfast cereals. This has nutritional implications in terms of glycaemic index and loading of breakfast cereals. Further work is required to develop clearer associations between the events of starch gelatinisation during extrusion and the potential glycaemic response.

Fouling of heat treatment equipment in the dairy processing industry is an expensive and persistent problem. The objective of this work was to develop a better understanding of the mechanisms of dairy fouling in heat exchangers and identify methods to control this build-up. This was part of a larger project investigating the interaction between spore-forming thermophilic bacilli (thermophiles) contamination and fouling deposits on internal surfaces of equipment. Two systems were developed to monitor the onset and build-up of fouling on the internal surfaces of two research heat exchangers. The first used a commercial sensor to measure the local heat flux and the temperature on the hot side of a plate type heat exchanger. The heat transfer coefficient was calculated and normalised with its value at the start of the run to reflect the contribution of fouling deposits to the thermal resistance, thus giving a real-time estimate of the rate of fouling. The second system used an energy balance over a tubular type heat exchanger and measured inlet and outlet temperatures to estimate the overall heat transfer coefficient thus giving a global measurement of fouling over the tubular heat exchanger. In both systems the plot of normalised heat transfer coefficient over time often stayed constant over an induction period, which was followed by a falling period indicative of growth in the fouling layer thickness and/or mass. Each system was validated by comparing the final value of the normalised heat transfer coefficient with direct measurements of fouling made at the end of a run namely: fouling deposit height for the local measurement and fouling deposit mass for the global measurement. The normalised heat transfer coefficient reported by each system correlated well with the corresponding direct measurement of the fouling layer. An important factor identified in this study was the effect of air bubble nucleation on fouling deposits. It was shown that bubbles that formed on the heated surface greatly reduced the length of the induction period to a matter of seconds rather than hours, as found in previous studies of fouling in the absence of surface bubbles. The rate of fouling was also enhanced while the bubbles remained at the surface. The structure of bubble type fouling layers was linked to the behaviour of the bubbles at the heated surface. Visual observations of these bubbles showed evidence of growth, vibration and coalescence during their period of attachment to the heated surface. Deposits from bubble type fouling consisted of all solid components found in the original milk solution, except lactose, in approximately the same ratio. By contrast fouling deposits reported in the literature with systems operating under the traditional protein denaturation mechanism were reported to consist mainly of whey proteins. Bubble induced fouling can be limited in a number of ways, the most effective being to maintain a high operating pressure in the equipment to ensure nucleation does not occur. Experiments conducted in this study showed that a pressure of 130 kPa.g was sufficient to suppress all bubble nucleation at the heated surface at a temperature of 90°C. Another method identified was the use of high linear fluid velocities to entrain any surface bubbles into the processing stream immediately upon nucleation. Linear velocities above 1.0 m/s were shown to achieve this goal in the miniature plate heat exchanger tested. However, this method is only partially successful because the local linear velocity varies with position in heat exchange equipment of complex geometries and can drop below the mainstream average velocity causing surface bubbles to form, especially in recirculation regions behind flow obstacles. A more reliable method, in situations where high operating pressures could not be used, involved conditioning the heated surface with a thin protein layer during the first few minutes of a run. Conditioning the surface resulted in bubble suppression even at high temperatures and low pressures, thus greatly extending the length of the induction period. Trials performed in this study showed that the addition of a proteolytic enzyme produced by psychrotrophic microbes greatly increased fouling. The enzyme destabilised the caseins which could attach directly to the heat exchange surface independently from the bubble fouling mechanism. Thus the quality of the milk is another important factor to consider. However, the addition of enzymes produced by thermophilic bacilli isolated from milk powder plants did not increase fouling. A theory describing the air bubble induced fouling mechanism is presented along with recommendations on how to reduce this fouling contamination in processing equipment.

Xenos Ltd. is a technology driven food company, that specializes in aseptic processing and packaging beverage products in bottles. Their aseptic filling technology is based on packaging sterilization with combined treatments of oxidizing agents and Ultraviolet radiation. Recent research studies have suggested that there is a synergistic effect of hydrogen peroxide (0.5 – 1 %) plus UV on inactivation of microorganisms including spores. Advantages of the combined treatment include rapid inactivation, minimum hydrogen peroxide residue in products, with the method being applicable to a wide range of packaging types. Based on this principle, a unique aseptic packaging technique has been developed by Xenos Ltd., which utilizes the combination of vaporized Perform (a commercial sterilizing agent manufactured by Orica Chemnet containing 25% hydrogen peroxide and 5% peracetic acid) and UV radiation at 7.5 – 12.5 W/m2. The aim of the project was to improve and validate the effectiveness of the packaging sterilization process through challenge tests. Challenge tests were conducted using Bacillus subtilis spores as the test microorganism to determine the log reductions delivered by the packaging sterilization system. The tests were firstly carried out on a pilot plant scale aseptic filling machine, in order to test the sterility of the small scale system, and investigate processing parameters (operational conditions) which could affect and improve sterility. The established operational conditions for achieving target sterility were used for designing and modifying an upgrade aseptic packaging system. Finally validation of the upgrade packaging sterilization system was conducted through challenge tests to prove sterility. It is highly recommended that in order to ensure sterility, the packaging sterilization system with vaporized Perform plus UV treatment must meet the requirements listed below during the sterilization process:  Hydrogen peroxide concentration of Perform condensate on bottles (after steaming) is best within 0.5 – 1 %;  Perform loading level should be minimum 300 mg/bottle after vaporized Perform treatment;  UV treatment time applied is greater than 2 seconds during UV treatment;  At least 20 seconds of penetration time (time between Perform treatment and UV treatment) should be allowed. The upgrade sterilization system used by Xenos Ltd. has been improved to meet the above operational conditions. With spore loading level of 106 per bottle and 105 per cap, the system is able to deliver at least a 6 log reduction of B. subtilis spores on PET or glass bottles and a 5 log reduction on bottle caps. Moruzzi et al. (2000) stated that at least a 4 log reduction is commercially required for an aseptic packaging process. Therefore, the system’s sterility would meet the commercial acceptable sterility.

The food industry could potentially benefit from using pervaporation, a membrane process, to concentrate flavours. This research aimed to investigate its application for concentrating flavours in dairy process streams. Pervaporation experiments were carried out at a range of operating conditions, using hydrophobic membranes. The feed mixtures were either aqueous model solutions of dairy flavour compounds (acids, esters and ketones), complex model mixtures containing flavour compounds plus non-volatile dairy components, or real dairy products. Flavour compound enrichment factors ranged from below one to above 30, with esters and ketones being concentrated more effectively than acids. Thus, the flavours could be partially fractionated based on their chemical structure. The permeation of acids was reduced by approximately 50% when the feed pH was increased to near their p Ka values. For flavour compounds with lower molecular weights than approximately 1 20 g mol- I , permeation was controlled mainly by sorption i n the membrane; for larger compounds it was controlled mainly by diffusion through the membrane. The mass transfer of each flavour compound increased with temperature, following an Arrhenius-like relationship. The activation energy was a function of each compound's heat of sorption, its molecular weight, and the elastic modulus of the membrane. The activation energy was also related to the Arrhenius preexponential factor. Thus, fluxes could be estimated through empirical correlations. The non-volatile feed composition was an important factor influencing the pervaporation performance. Milk protein isolate (4% w/v) or lactose (6% or 1 2% w/v) bound with the flavour compounds in the feed, thus lowering the enrichment of sorption-controlled compounds. Milk fat (up to 38% w/v, in the form of cream ) reduced the enrichment of all the flavour compounds tested. Esters and ketones became unavailable for pervaporation as they partitioned into the fat phase; acids remained mainly in the aqueous phase, but their permeation was reduced because the added cream increased the feed pH. Experiments with real dairy products showed that pervaporation could be used to concentrate diacetylin starter distillate, and to selectively recover short-chain esters from ester cream. Of these two products, starter distillate is the more promising for use as a pervaporation feed stream.

The main objective of this study was to determine the effects of batters containing various flour types and frying methods on physical and chemical properties of chicken fingers. To determine the effects of different flour types, 30 % of the corn and wheat flour mix in control batter was replaced with chickpea, rice or soy flours. Frying was performed in microwave oven at 365 W (70 %) power level and at 180&amp / #61617 / 1&deg / C for different times. Samples were also fried in a conventional fryer at 180&amp / #61617 / 1&deg / C for comparison. The properties that were measured were coating pick-up and moisture content, oil content, color, hardness, porosity and acrylamide content of fried samples. In addition, microstructural analysis of batters and temperature distribution of fried samples during cooling were performed. Moisture content of chicken fingers decreased whereas the darkness, porosity and hardness of samples increased with increasing microwave frying time. Using microwaves decreased frying time by 70 %. Samples fried for 1.5 min using microwave provided similar moisture and oil contents in the coating part as compared to conventionally fried ones for 5min. However, the chicken part of microwave fried sample had lower moisture content. Lighter colored samples with higher porosity and lower hardness values were obtained with microwave frying. In microwave frying, soy flour addition to batter formulation decreased the moisture loss and oil absorption as compared to control by 19.3% and 20.7%, respectively. The lowest hardness, the highest porosity and oil content were obtained with the addition of chickpea flour. Flour type was not found to be effective on acrylamide content. Microwave frying provided lower acrylamide content as compared to those fried conventionally for all types of flours. The reduction in acrylamide level was the highest (34.5%) for rice flour containing batter. Color parameters of chicken fingers were not found to be a reliable indicator of acrylamide levels. Different types of frying method and flours used in batter formulation resulted in differences in the microstructure of fried batter. Variations in internal temperature distribution during cooling increased with frying time in both microwave and conventional frying. The sample fried in microwave oven for 1.5 min had a more nonuniform temperature distribution.

High pressure applications are alternatives to conventional methods in food processing. They provide interesting modifications in food structures which leads to new product formulations. The aim of this study is to identify the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP) on stability and rheological properties of model oil-in-water emulsions. Microfluidization was selected among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared to the coarse emulsions which were prepared with colloid mill homogenization. Stability of emulsions was determined comparatively by using an analytical photo-centrifuge device employing a novel analysis technology. Whey protein isolate (WPI) was used as an emulsifier in combination with a food polysaccharide as a stabilizer. The polysaccharides used were xanthan gum, guar gum and locust bean gum which are widely used stabilizing ingredients in food industry. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities. The finer emulsions obtained with this homogenization technique led to distinctive improvements in emulsion stability. On the other hand, the improvements in stability by HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations with higher oil content. Apart from these, HHP treatment was found to be relatively more contributing to the enhancements in viscoelastic properties.

The aim of this study is to design a mixer with appropriate parts for uniform treatment of the material in household microwave ovens which can not be achieved with the turntable. The designed mixer&rsquo / s performance was tested by the help of color and surface temperature values. In the design of the mixer primarily mixing in the vertical and radial directions were sought and for this purpose blades and wings for directing the material especially in these directions were present. The rotational motion of the mixer was provided by a shaft actuated by the motor of the turntable where the motor was replaced by a speed adjustable one. Couscous macaroni beads wetted with CoCl2 solution were dried for processing in the microwave oven. The initial color values of the samples were L*= 52.0&plusmn / 0.35, a*= 8.8&plusmn / 0.21 and b*= 14.1&plusmn / 0.11 . The studied parameters were microwave power level (10%, 40%, 67% and 100% ), processing time (60,90, 120 sec), speed of rotation of the mixer (5,10,15 rpm) , location (4up, 4bt, 6up, 6bt) for the cases of with and without the mixer. v The macaroni beads were well arranged in a mixing container and then put into the microwave oven for operation. Same parameters with coloring experiments were used for the surface temperature determination. After operation the container was photographed by an IR camera. Whether the designed mixer was present or not, average a* and b* values decreased while temperature increased . All these values were significantly affected by the time and power increase. The L* value became an insignificant parameter to decide for the performance Location of the particles in the container appeared as a significant parameter affecting the a*, b* and temperature values without the mixer whereas, with the use of the mixer it became an insignificant parameter indicating uniform energy distribution. Speed of rotation of the mixer was a significant parameter for both cases. However, the color values obtained did not show the same trend with mixer which it showed without mixer. It is concluded that the designed mixer is effective in providing homogeneity of the product by providing sufficient mixing in the container hence the particles can receive about equal energy. Keywords: Microwave oven, particulate solids, mixing, mixer design, testing performance, uniform treatment

The purpose of this research was to determine the solubility of apricot (Prunus armeniaca L.) oil in supercritical carbon dioxide (SC-CO2), effects of parameters (particle size, solvent flow rate, pressure, temperature and co-solvent (ethanol) concentration) on extraction yield and to investigate the possibility of fractionation. Solubility, increased with pressure and increased with temperature above the crossover pressure, which was found between 200 and 300 bar, and decreased with temperature below the crossover pressure. Appropriate models were fitted to data. Extraction of apricot kernel oil occurred in two extraction periods as fast and slow extraction periods. Most of the oil was extracted in the fast extraction period and the oil recovered in the slow extraction period was negligible. Extraction yield increased with decrease in particle size and recovery of more than 99 % of the oil was possible if particle diameter decreased below 0.425 mm. Extraction rate increased with increase in flow rate, pressure, temperature and ethanol concentration. The volume mass transfer coefficient in the fluid phase changed between 0.6 and 3.7 /min, whereas the volume mass transfer coefficient in the solid phase changed between 0.00009 and 0.00048 /min. Extraction yield at 15 min for particle diameter smaller than 0.85 mm was formulated as a function of solvent flow rate, pressure, temperature, and ethanol concentration by using Response Surface Methodology. According to the model yield was highest (0.26 g /g) at 4 g/min flow rate, 60 oC, 450 bar and 3 % ethanol concentration. Fractionation was not possible at significant levels.

The main objective of this study was to optimize the processing conditions of breads baked in halogen lamp-microwave combination oven by using response surface methodology. It was also aimed to construct neural network models for the prediction of quality parameters of bread as a function of processing conditions. Different baking time and power combinations were used in order to find the optimum baking conditions of bread in halogen lamp-microwave combination oven. The independent variables were the baking time (4, 4.5, 5, 5.5, and 6 min), power of upper and lower halogen lamps (40, 50, 60, 70, and 80%), and power of the microwave (20, 30, 40, 50, and 60%). As control, breads baked in conventional oven at 200&ordm / C for 13 min were used. The measured quality parameters were the weight loss, color change, specific volume, porosity, and texture profile of the breads. Baking time, upper halogen lamp power, and microwave power were found to be significant on affecting most of the quality parameters. On the other hand, lower halogen lamp power was found to be an insignificant factor for all of the responses. For the optimization process, Response Surface Methodology (RSM) was used. The optimum baking conditions were determined as 5 min of baking time at 70% upper halogen lamp power, 50% lower halogen lamp power, and 20% microwave power. Breads baked at the optimum condition had comparable quality with conventionally baked ones. When halogen lamp-microwave combination oven was used, conventional baking time of breads was reduced by 60%. Artificial neural network models were developed for each of the quality parameters in order to observe the effects of the baking time and different oven conditions on the quality of the breads. High regression coefficients were calculated between the experimental data and predicted values showing that this method is capable in predicting quality parameters of breads during halogen lamp-microwave combination baking. In addition, the results were comparable to the RSM study.