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A 3-dimensional (3-D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near-perfect 3-D geometries of food package and microwave oven were used. A... more
A 3-dimensional (3-D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near-perfect 3-D geometries of food package and microwave oven were used. A multiphase porous media model combining the electromagnetic heat source with heat and mass transfer, and incorporating phase change of melting and evaporation was included in finite element model. Discrete rotation of food on the turntable was incorporated. The model simulated for 6 min of microwave cooking of a 450 g frozen lasagna kept at the center of the rotating turntable in a 1200 W domestic oven. Temperature-dependent dielectric and thermal properties of lasagna ingredients were measured and provided as inputs to the model. Simulated temperature profiles were compared with experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. The total moisture loss in lasagna was predicted and compared with the experimental moisture loss during cooking. The simulated spatial temperature patterns predicted at the top layer was in good agreement with the corresponding patterns observed in thermal images. Predicted point temperature profiles at 6 different locations within the meal were compared with experimental temperature profiles and root mean square error (RMSE) values ranged from 6.6 to 20.0 °C. The predicted total moisture loss matched well with an RMSE value of 0.54 g. Different layers of food components showed considerably different heating performance. Food product developers can use this model for designing food products by understanding the effect of thickness and order of each layer, and material properties of each layer, and packaging shape on cooking performance.
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A 3-dimensional (3-D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near-perfect 3-D geometries of food package and microwave oven were used. A... more
A 3-dimensional (3-D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near-perfect 3-D geometries of food package and microwave oven were used. A multiphase porous media model combining the electromagnetic heat source with heat and mass transfer, and incorporating phase change of melting and evaporation was included in finite element model. Discrete rotation of food on the turntable was incorporated. The model simulated for 6 min of microwave cooking of a 450 g frozen lasagna kept at the center of the rotating turntable in a 1200 W domestic oven. Temperature-dependent dielectric and thermal properties of lasagna ingredients were measured and provided as inputs to the model. Simulated temperature profiles were compared with experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. The total moisture loss in lasagna was predicted and compared with the experi...
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Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and... more
Cronobacter sakazakii and Salmonella species have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. Cronobacter sakazakii and Salmonella spp. can survive the spray-drying process if milk is contaminated after pasteurization, and the dried product can be contaminated from environmental sources. Compared with conventional heating, radio-frequency dielectric heating (RFDH) is a faster and more uniform process for heating low-moisture foods. The objective of this study was to design an RFDH process to achieve target destruction (log reductions) of C. sakazakii and Salmonella spp. The thermal destruction (decimal reduction time; D-value) of C. sakazakii and Salmonella spp. in NDM (high-heat, HH; and low-heat, LH) was determined at 75, 80, 85, or 90 °C using a thermal-death-time (TDT) disk method, and the z-values (the temperature increase required to obtain a decimal reduction of ...
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Abstract: Thermal destruction of microorganisms has been proven to be the most effective way of decontaminating food to ensure food safety. Electromagnetic radiation in the microwave and radio frequency ranges can penetrate food materials... more
Abstract: Thermal destruction of microorganisms has been proven to be the most effective way of decontaminating food to ensure food safety. Electromagnetic radiation in the microwave and radio frequency ranges can penetrate food materials and generate heat from within the products. By taking advantage of this property, microbiological decontamination of food materials can be accomplished. In order to exploit the benefits of this technology, a deeper understanding of the interaction of these non-ionizing electromagnetic radiations, with various food matrices, is required. Furthermore, due to the organic nature of the microorganisms along with their high moisture content within the cell constituents, there are studies showing enhanced thermal destruction kinetics in certain food materials during the application of these radiations. Despite these advantages, this technology is not very popular for food decontamination, primarily due to its relatively high capital cost and extreme non- uniformity in solid food applications. This chapter will focus on the principles of dielectric heating, application of this technology for food decontamination and their respective advantages and disadvantages.
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A 3-dimensional finite-element model coupling electromagnetics and heat and mass transfer was developed to understand the interactions between the microwaves and fresh mashed potato in a 500 mL tray. The model was validated by performing... more
A 3-dimensional finite-element model coupling electromagnetics and heat and mass transfer was developed to understand the interactions between the microwaves and fresh mashed potato in a 500 mL tray. The model was validated by performing heating of mashed potato from 25 °C on a rotating turntable in a microwave oven, rated at 1200 W, for 3 min. The simulated spatial temperature profiles on the top and bottom layer of the mashed potato showed similar hot and cold spots when compared to the thermal images acquired by an infrared camera. Transient temperature profiles at 6 locations collected by fiber-optic sensors showed good agreement with predicted results, with the root mean square error ranging from 1.6 to 11.7 °C. The predicted total moisture loss matched well with the observed result. Several input parameters, such as the evaporation rate constant, the intrinsic permeability of water and gas, and the diffusion coefficient of water and gas, are not readily available for mashed po...
Research Interests: Chemical Engineering, Chemistry, Food Science, Water, Microwave, and 14 moreModeling, Finite element method, Sensitivity Analysis, Medicine, Heat and Mass Transfer, Cooking, Moisture, Microwave Heating, Theoretical Models, Microwaves, Reproducibility of Results, Food Sciences, Solanum Tuberosum, and Water Content
Research Interests: Computer Science, Materials Science, Biomedical Engineering, Microwave, Medicine, and 15 moreComputer assisted orthopaedic surgery, Computer Simulation, Liver, Animals, Feasibility Studies, Body Temperature, Cattle, Body water, Microwaves, Ablation, Gases, Electrical And Electronic Engineering, Microwave Ablation, Hepatectomy, and In Vitro Techniques
Research Interests: Materials Science, Food Science, Food Engineering, Microwave, Modeling, and 11 moreHeat Transfer, Food Processing, Electrical and Electronics, Power and Energy, Microwave Heating, Thermal, Food Sciences, Agricultural and Bioresource Engineering, Thermal Image, electromagnetic heating , and Finite Difference Time Domain Method
ABSTRACT A finite element model coupling electromagnetic and heat transfer equations was developed to understand complex microwave interactions in food. The model simulated rotation of a frozen multi-component meal consisting of nine... more
ABSTRACT A finite element model coupling electromagnetic and heat transfer equations was developed to understand complex microwave interactions in food. The model simulated rotation of a frozen multi-component meal consisting of nine chicken nuggets and mashed potatoes. Temperature-dependent dielectric and thermophysical properties of chicken nuggets and mashed potatoes were measured as a function of temperature from −10 °C to 110 °C. The model included detailed cavity geometry, phase change, and rotation of the food. Effect of rotation angle on temperature predictions was studied and a 45° rotation angle was found to be sufficient. Simulated temperature profiles were compared with experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. Predicted spatial surface temperature profile was in good agreement with the corresponding experimental profiles in terms of hot and cold spot patterns. The root mean square error values ranged from 5.8 °C to 26.2 °C in chicken nuggets as compared 4.3–4.7 °C in mashed potatoes. The predicted and experimental temperature profiles were provided as inputs to a microbial inactivation kinetics model for Salmonella Heidelberg to assess food safety risks in chicken nuggets. For 90 s of cooking in a 1200 W microwave oven, at least 7-log reductions of Salmonella Heidelberg was not achieved completely at all locations in the chicken nuggets due to non-uniform heating. The validated model can be used to optimize the layout and food system/package modification to achieve more uniform heating.
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Current quarantine method, fumigation with methyl bromide, for fresh fruit is under international pressure to phase out because methyl bromide damages the ozone layer. To develop alternative methods, many researchers have explored use of... more
Current quarantine method, fumigation with methyl bromide, for fresh fruit is under international pressure to phase out because methyl bromide damages the ozone layer. To develop alternative methods, many researchers have explored use of non-chemical treatment methods. But all these methods have their own limitations. For example, conventional hot water treatment takes long time which results in undesirable quality changes in treated fruit. Radio frequency (RF) heating has been looked upon as a means to shorten thermal treatment time. In this study, RF heating patterns in orange, apple, grapefruit, peach, and avocado were investigated. The selected fruits were placed in a fruit mover and RF heated in a 12 kW parallel plate RF unit operating at 27.12 MHz. Dielectric properties of each fruit constitutional part were measured by open-ended coaxial cable probe method. The study showed that peel dielectric properties along with peel thickness greatly influenced the RF heating behavior of an orange and a grapefruit. Core heating was prominent in apple, peeled orange and grapefruit; whereas in whole oranges the subsurface was at higher temperature than the core. The study helped in better understanding of the complex RF heating characteristics of fruits for designing practical product specific treatment protocol.