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Ohmic Heating (ohmic + heating)
Selected AbstractsPHYSICAL PROPERTIES OF FISH PROTEINS COOKED WITH STARCHES OR PROTEIN ADDITIVES UNDER OHMIC HEATINGJOURNAL OF FOOD QUALITY, Issue 5 2007PANIDA PONGVIRAT CHAI ABSTRACT The texture, color and microstructure of surimi seafood gels were investigated to determine the interaction effects of fish proteins with starches or protein additives under ohmic heating, and to compare ohmically cooked gels with conventional water-bath-cooked gels. Gel properties were affected by the type of additive, concentration and cooking method. The effect of starch on gel texture was more pronounced at low concentrations. Compared to wheat starch, potato starch seemed to slightly improve gel strength; however, it decreased the gel whiteness. All nonfish protein additives resulted in better or equal textural properties of gels, whereas there was a slightly negative effect for gel color. Fast ohmic-cooked gels mostly exhibited higher gel strength than conventionally cooked gels. PRACTICAL APPLICATIONS There is a discrepancy between current gel preparation (slow heating by water bath) and current practice of crabstick manufacturing (fast heating). The use of data generated from slow cooking gel preparation for the manufacture of fast cooking crabstick does not make sense. This study demonstrates how starch and protein additives behave at ohmic heating which mimics the fast cooking crabstick manufacture. [source] The Effect of Electric Field on Important Food-processing Enzymes: Comparison of Inactivation Kinetics under Conventional and Ohmic HeatingJOURNAL OF FOOD SCIENCE, Issue 9 2004I. Castro ABSTRACT: This work deals with the determination of the inactivation kinetics of several enzymes, most of them used as time-temperature integrators in the food industry. The tested enzymes were polyphenoloxidase, lipoxygenase, pectinase, alkaline phosphatase, and p-galactosidase, and the inactivation assays were performed under conventional and ohmic heating conditions. The thermal history of the samples (conventional and ohmically processed) was made equal to determine if there was an additional inactivation caused by the presence of an electric field, thus eliminating temperature as a variable. All the enzymes followed 1st-order inactivation kinetics for both conventional and ohmic heating treatments. The presence of an electric field does not cause an enhanced inactivation to alkaline phosphatase, pectinase, and ,- galactosidase. However, lipoxygenase and polyphenoloxidase kinetics were significantly affected by the electric field, reducing the time needed for inactivation. The results of the present work can be used industrially to determine processing effectiveness when ohmic heating technology is applied. [source] DIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] Ohmic heating of dairy fluids,effects of local electric field on temperature distributionASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Heng Jin Tham Abstract This paper presents the heat transfer model of a continuous flow ohmic heating process. The model fluid used was a mixture of reconstituted skimmed milk and whey protein concentrate solution. Two-dimensional numerical simulations of an annular ohmic heater were performed using a general purpose partial differential equation solver, FlexPDE. The momentum, energy, and electrical equations were solved for a laminar flow regime. Two models were used to determine the volumetric heating rate, one taking into account the local electric field by solving the Laplace equation while another model assumes an average voltage gradient applied between the two electrodes. Results show that while the wall temperature distribution is different for the two cases, the bulk fluid temperature and the average outlet temperature are the same. The predicted temperatures generally agree well with the measured temperatures. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Application of High Current and Current Zero Simulations of High-Voltage Circuit BreakersCONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2006C. M. Franck Abstract This paper reports on the use of computational fluid dynamic (CFD) simulations to predict the interruption behaviour of high-voltage circuit breakers (HV-CB) using the self-blast principle. Two different levels of accuracy of the arc model are proven to be sufficiently accurate for simulating the high-current phase and the period around current zero (CZ). For the high-current phase, a simplified equivalent model of the arc is implemented to predict the pressure build-up, and even more important to accurately trace the hot gas from the arcing zone into the exhausts and the heating volume. A detailed analysis of the gas mixing in the heating volume for different arcing times and current amplitudes showed the optimum geometrical design of the heating volume. For the CZ phase, a more detailed arc model is needed including the effects of ohmic heating, radiative energy transfer, and turbulent cooling fully resolved in space and time. The validation with experiments was done and shows good agreement which justifies the use of the implemented model. With it, scaling laws varying only one parameter at a time (pressure and applied current slope) were derived and confirm previously found empirical laws. This is of particular interest, as it is very difficult to derive such scaling laws from experiments where the scatter is always very large and where it is impossible to vary only one parameter at a time. The influence of the most important geometrical parameters of the nozzle on the interruption performance is shown. In addition to previous experimental indications of this, the simulation reveals that turbulent cooling on the arc edge is the main reason for the difference in interruption performance. Moreover, the exact spatio-temporal build-up of arc resistance and with it the detailed understanding of the arc interruption process is possible and shown here for the first time. These simulations enable us to predict HV-CB performance and to minimise the number of development tests and are routinely used in new development projects. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Merging formation and current amplification of field-reversed configurationIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2007Michiaki Inomoto Member Abstract The merging formation of the field-reversed configuration (FRC) has been developed in the TS-3 merging experiment, leading us to a new scenario of FRC slow formation, heating and current amplification. Two force-free spheromaks with opposing toroidal fields were merged together in the axial direction to form a high-, FRC with higher efficiency than the conventional field-reversed theta-pinch method. This unique relaxation from the force-free (, , 0.05 , 0.1) spheromaks to the high-, (, , 0.7 , 1) FRC is attributed to the conversion of toroidal magnetic energy into ion thermal energy through the reconnection outflow. A central ohmic heating (OH) coil worked successfully to amplify the FRC plasma current by a factor of 2. Toroidal mode analysis of magnetic structure indicated that the tilting stability of the oblate FRC was provided by an ion kinetic effect. This oblate FRC is also useful as an initial equilibrium to produce a high-,p spherical tokamak (ST) with diamagnetic toroidal magnetic field, suggesting the close relationship between FRCs and high-,p STs in the second stable region of the ballooning mode. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] DIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY-STATE TEMPERATURE,JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2001MARYBETH LIMA ABSTRACT Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady-state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized. [source] PHYSICAL PROPERTIES OF FISH PROTEINS COOKED WITH STARCHES OR PROTEIN ADDITIVES UNDER OHMIC HEATINGJOURNAL OF FOOD QUALITY, Issue 5 2007PANIDA PONGVIRAT CHAI ABSTRACT The texture, color and microstructure of surimi seafood gels were investigated to determine the interaction effects of fish proteins with starches or protein additives under ohmic heating, and to compare ohmically cooked gels with conventional water-bath-cooked gels. Gel properties were affected by the type of additive, concentration and cooking method. The effect of starch on gel texture was more pronounced at low concentrations. Compared to wheat starch, potato starch seemed to slightly improve gel strength; however, it decreased the gel whiteness. All nonfish protein additives resulted in better or equal textural properties of gels, whereas there was a slightly negative effect for gel color. Fast ohmic-cooked gels mostly exhibited higher gel strength than conventionally cooked gels. PRACTICAL APPLICATIONS There is a discrepancy between current gel preparation (slow heating by water bath) and current practice of crabstick manufacturing (fast heating). The use of data generated from slow cooking gel preparation for the manufacture of fast cooking crabstick does not make sense. This study demonstrates how starch and protein additives behave at ohmic heating which mimics the fast cooking crabstick manufacture. [source] A Critical Review of Milk Fouling in Heat ExchangersCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 2 2006Bipan Bansal ABSTRACT Fouling of heat exchangers is a problem in the dairy industry and costs billions of dollars every year. It has been studied extensively by researchers around the world, and a large number of studies are reported in the literature. This review focuses on the mechanisms of milk fouling, investigating the role of protein denaturation and aggregation as well as mass transfer. We also endeavor to review the effect of a number of factors which have been classified into 5 categories: (1) milk quality, (2) operating conditions, (3) type and characteristics of heat exchangers, (4) presence of microorganisms, and (5) transfer of location where fouling takes place. Different aspects have been discussed with the view of possible industrial applications and future direction for research. It may not be possible to alter the properties of milk since they are dependent on the source, collection schedule, season, and many other factors. Lowering the surface temperature and increasing the flow velocity tend to reduce fouling. Reducing the heat transfer surface roughness and wettability is likely to lower the tendency of the proteins to adsorb onto the surface. The use of newer technologies like microwave heating and ohmic heating is gaining momentum because these result in lower fouling; however, further research is required to realize their full potential. The presence of microorganisms creates problem. The situation gets worse when the microorganisms get released into the process stream. The location where fouling takes place is of paramount importance because controlling fouling within the heat exchanger may yield little benefit in case fouling starts taking place elsewhere in the plant. [source] | ||||||||||