Modelling and analysis of a radio frequency dielectric heating for defatted soy flour

Abstract: In this paper a Radio Frequency (RF) method for drying defeated soy flower is developed using a class E amplifier. The raw and uncooked soy flour contains a few undesirable inherent soybean enzymes. Minimizing the content and effect of these enzymes usually is done through “drying/heating” methods. The method used in this study is “RF dielectric heating”. Modelling, simulation and implementation results complete the paper

Radio frequency dielectric heating and hyperspectral imaging of common foodborne pathogens

Doctor of PhilosophyDepartment of Food ScienceRandall K. PhebusIntervention techniques to control foodborne pathogens, and rapid identification of pathogens in food are of vital importance to ensure food safety. Therefore, the first objective of this research was to study the efficacy of radio frequency dielectric heating (RFDH) against C. sakazakii and Salmonella spp. in nonfat dry milk (NDM) at 75, 80, 85, or 90°C. Using thermal-death-time (TDT) disks, D-values of C. sakazakii in high heat (HH)- and low heat (LH)-NDM were 24.86 and 23.0 min at 75°C, 13.75 and 7.52 min at 80°C, 8.0 and 6.03 min at 85°C, and 5.57 and 5.37 min at 90°C, respectively. D-values of Salmonella spp. in HH- and LH-NDM were 23.02 and 24.94 min at 75°C, 10.45 and 12.54 min at 80°C, 8.63 and 8.68 min at 85°C, and 5.82 and 4.55 min at 90°C, respectively. The predicted (TDT) and observed (RFDH) destruction of C. sakazakii and Salmonella spp. were in agreement, indicating that the organisms' behavior was similar regardless of the heating system (conventional vs. RFDH). However, RFDH can be used as a faster and more uniform heating method for NDM to achieve the target temperatures. The second objective of this research was to study if hyperspectral imaging can be used for the rapid identification and differentiation of various foodborne pathogens. Four strains of C. sakazakii, 5 strains of Salmonella spp., 8 strains of E. coli, and 1 strain each of L. monocytogenes and S. aureus were used in the study. Principal component analysis and kNN (k-nearest neighbor) were used to develop classification models, which were then validated using a cross-validation technique. Classification accuracy of various strains within genera including C. sakazakii, Salmonella spp. and E. coli, respectively was 100%; except within C. sakazakii, strain BAA-894, and within E. coli, strains O26, O45 and O121 had 66.67% accuracy. When all strains were studied together (irrespective of their genera) for the classification, only C. sakazakii P1, E. coli O104, O111 and O145, S. Montevideo, and L. monocytogenes had 100% classification accuracy; whereas, E. coli O45 and S. Tennessee were not classified (classification accuracy of 0%)

Effect of radio frequency dielectric heating on functionality of nonfat dry milk

Master of ScienceFood Science InstituteKaren A. SchmidtRadio frequency dielectric heating (RFDH) can provide rapid and uniform heating throughout the products' mass, and can be used to bake, dry, and defrost foods. Studies have shown that when RFDH induced a 5-log reduction of Salmonella spp. in nonfat dry milk (NDM), whey protein nitrogen index (WPNI) decreased, suggesting that functional properties of the NDM might be impacted. This research was conducted to determine if RFDH affected the functional properties of NDM [high-heat (HH) and low-heat (LH)]. Nonfat dry milk were treated to 75, 80 and 85°C in the RFDH unit, then were held for 125, 63 and 43 min for LH-NDM or 115, 52 and 43 min for HH-NDM, and cooled to ~23 ± 1°C. Powders were evaluated for WPNI , nitrogen solubility index, and color. Maillard browning and functional properties of NDM samples were evaluated after NDM was rehydrated to 3.5% protein with deionized water, and adjusted to pH 7.00. Glucono-delta-lactone was added in rehydrated NDM (3.5% protein; natural pH) as an acidifying agent to form milk gels, and the physical properties of the gels were determined. Two replications were conducted and data were analyzed with two-way ANOVA (RFDH and NDM) and Tukey mean differentiations (p ≤ 0.05). Results showed that LH-NDM (collapsed for RFDH treatments) had 5.7% less viscosity, 20.9% less overrun, 27.4% less foam stability, as well as 15% less water holding capacity compared with HH-NDM (collapsed for RFDH treatments). This can be explained by the natural whey protein denaturation differences in the HH-NDM and LH-NDM. Viscosity and surface tension were impacted by the RFDH treatment. NDM (HH and LH) treated to 85°C had 10% greater viscosity than the control, and the NDM treated to 75°C had less surface tension compared with samples treated to 80°C, 85°C and the control. Overall, RFDH decreased WPNI in LH-NDM, but not HH-NDM. The SDS-PAGE gel images provided supportive evidence to the WPNI results. RFDH is a processing technology that could change a few functional properties of NDM in this study, which makes it a promising method that may be further exploited for various food applications, such as emulsifiers, foaming agents, etc. However, potential negative impacts, such as color change caused by Maillard reaction, loss of WPNI in LH-NDM, cannot be neglected

An assessment of improved functionality of radio frequency dielectric heated nonfat dry milk into model food systems

Master of ScienceFood Science InstituteKaren A. SchmidtThe application of a dry heat processing technology, such as radio frequency dielectric heating (RFDH) on nonfat dry milk (NFDM), has been proven to inactivate pathogens and to alter functional properties. The altered functional properties of RFDH-treated NFDM could produce a valuable, novel ingredient that may improve final product quality when used in other food systems. However, dependent upon the RFDH conditions, whey protein denaturation can occur in low-heat NFDM (LH), which in turn impacts functional properties. To understand how RFDH-treated NFDM influences the functional properties in a variety of food systems, RFDH-treated LH was the milk source in the manufacture of bread, white sauce, and caramels. Low-heat NFDM was RFDH-treated ((heated to 85°C and held for 90 min (85/90) or 180 min (85/180)) and cooled. For bread, white sauce, and caramel, the NFDM samples ((LH, 85/90, 85/180, and high heat (HH)) were directly added into formulations. Three replications were completed and all data were analyzed using SAS statistical software to differentiate amongst the significant means. Within bread, the 85/90 and 85/180 displayed similar physical properties such as loaf volume, crumb firmness, and color properties when compared to HH. In white sauce, the 85/180 functioned similar to HH as these sauces had similar firmness, water-holding capacity, and color (darkness). When formulated within caramels, 85/90 and 85/180 displayed similar water activity, firmness, stickiness, and color properties as caramels produced with HH. Due to the nature of these particular food systems, it is possible that formulating with the RFDH-treated NFDM, will produce better quality finished products when compared to LH

The Characterization of Effective Electromagnetic Fields on the Safety and Quality of Low-Moisture Foods (EFFS) - Prototype Device Development

Contamination of low-moisture foods including flour, wheat grain, baby formula, and more, have increasingly become a concern due to sanitizing challenges. While industrial food processors have long used RF heating to sanitize mass quantities, an equivalent consumer device is absent from the market today. The Characterization of Effective Electromagnetic Fields on the Safety and Quality of Low-Moisture Foods (EEFS) project is an interdisciplinary effort to develop an RF heating consumer device to sanitize low-moisture foods. A prototype device was designed to sanitize low-moisture food items using RF heating acceptable for commercial or consumer applications

Disinfestation of rusty grain beetle (Cryptolestes ferrungineus) in stored wheat grain using 50-ohm radio frequency (RF) heating system

Non-chemical methods were proposed as alternatives for disinfestation of stored grains using fumigants and pesticides. Therefore, this thesis investigated the disinfestation of rusty grain beetle (Cryptolestes ferrungineus) in stored wheat grain using electromagnetic energy from 50-ohm radio frequency (RF) heating system. The objectives of this current study were to update the research outcomes of disinfestation using electromagnetic energy; investigate the installation process of the 50-ohm RF heating system; design and fabricate the parallel plate applicator; determine the mortality of rusty grain beetle; estimate parameters of thermal death kinetics during the RF heating of insects in stored grain; compare the quality of wheat grain before and after RF heating; and determine the heating uniformity in the designed applicator. The review showed that using electromagnetic energy for disinfestation might be possible without degrading the quality of the host materials. RF energy for disinfestation, however, was being preferred over microwave energy for its higher selective heating characteristics. The 100% mortality rates of adult rusty grain beetle were found at all moisture contents of the bulk wheat grain at the end temperatures of 70°C and 80°C. It was observed also that the complete mortalities at all life stages of the insects were achieved at 80°C target temperature at three moisture contents (12%, 15%, and 18%) of the bulk wheat samples. The simulated mortalities based on the model were in good agreement with the experimental mortalities. The determined thermal death kinetic parameters, Ea, K0, and n were 97,490 J/mol, 〖6.74 x 10〗^13 1/s, and 1, respectively. The results showed that disinfestation of insect pests in wheat grain using 50-ohm RF heating did not degrade the quality of the host material significantly. Nevertheless, the RF heating in the applicator was not uniform at all moisture contents and power levels. The temperature differences between the hottest and coldest spots at different MCs and power levels were 38.6°C at 3 kW, 38.7°C at 5 kW, and 39.1°C at 7 kW (12% MC) and 43°C at 3 kW, 43.6°C at 5 kW, and 41.9°C at 7 kW (18% MC). Non-uniform heating in the RF applicator has been a challenge in disinfestation using electromagnetic energy. Thus, suggestions for future studies were provided to solve the problem of heating uniformity in the applicator and the guidelines for a successful installation of 50-ohm RF heating system for disinfestation of insects in stored agricultural materials

Study of electromagnetic field uniformity in radio frequency heating applicator

A 6kW 27MHz pilot scale radio frequency (RF) heating system was developed at Washington State University for processing 6-pound packaged foods to achieve shelf-stability. Although RF heating presents the possibility of improving food quality in a shorter processing time than the conventional retort heating method, it still confronts the heating non-uniformity caused by fringe effects. The objectives of this research were to gain a better understanding of the dielectric heating process, to study the factors that may influence the RF heating pattern and heating rate, and to investigate the possibility of achieving heating uniformity during the RF heating process.To support this project, a dielectric properties measurement system was used to determine the complex permittivity of materials used in dielectric heating over a temperature range from 20 to 120 °C at radio frequencies (27 and 40 MHz) and microwave frequencies (915 and 1800 MHz). The dielectric properties of egg products were measured with an open-end coaxial probe method. The dielectric property information was used to adjust the electric conductivity of the circulating water that immersed the packaged foods and mitigated fringing electric field and edge-heating effects during the RF heating process, and to support the implementation of the computer simulating on RF heating process.Experiments and computer simulations using the finite element method were performed to study the influence of food dielectric properties and circulating water electric conductivity on RF heating rate and heating pattern. The results of this work indicated that with the increase of electric conductivity of circulating water or food loss factor, the heating rate decreased. Both the dielectric properties of food and electric conductivity of circulating water affected the electric field distribution inside the food.Experiments and computer simulations were also conducted on RF heating of a heterogeneous food, meat balls in lasagna. The results demonstrated that RF heating had a potential to process pre-packaged heterogeneous food. Proper distribution and suitable size of each component, though with vastly different dielectric properties, are possible to ensure relatively uniform RF heating

The Oil Shale Transformation in the Presence of an Acidic BEA Zeolite under Microwave Irradiation

The transformation of an oil shale sample from the Autun Basin in the Massif Central, France, was studied using two different heating strategies: microwave irradiation and conventional heating. Microwave heating was performed using a single-mode cavity operating at a frequency of 2.45 GHz under an inert atmosphere. Heating of the sample generated liquid products of similar composition using either microwave or conventional heating. The yields of liquid products were similar in the two cases, while the overall energy requirements were much lower using microwave irradiation. The influence of water vapor on the oil shale decomposition was also studied under microwave energy. In order to simulate conversion of the organic fraction of the oil shale in the presence of an acidic zeolite catalyst, the oil shale sample was mixed with 5 wt % BEA zeolite and heated under microwave irradiation. It was found that the liquid products yield decreased along with an increase in the amount of coke produced. Gaseous and liquid products recovered showed a tendency for the production of lighter components in the presence of zeolite. The aromatic character of the oils was more important when microwaves were used, especially in the presence of zeolite

Exposure of insects to radio-frequency electromagnetic fields from 2 to 120 GHz

Insects are continually exposed to Radio-Frequency (RF) electromagnetic fields at different frequencies. The range of frequencies used for wireless telecommunication systems will increase in the near future from below 6 GHz (2 G, 3 G, 4 G, and WiFi) to frequencies up to 120 GHz (5 G). This paper is the first to report the absorbed RF electromagnetic power in four different types of insects as a function of frequency from 2 GHz to 120 GHz. A set of insect models was obtained using novel Micro-CT (computer tomography) imaging. These models were used for the first time in finite-difference time-domain electromagnetic simulations. All insects showed a dependence of the absorbed power on the frequency. All insects showed a general increase in absorbed RF power at and above 6 GHz, in comparison to the absorbed RF power below 6 GHz. Our simulations showed that a shift of 10% of the incident power density to frequencies above 6 GHz would lead to an increase in absorbed power between 3-370%

Radiofrequency processing for inactivation of Salmonella spp. and Enterococcus faecium NRRL B-2354 in whole black peppercorn and ground black pepper

Black pepper has been implicated in several foodborne illness outbreaks and food product recalls due to Salmonella contamination. Conventional decontamination methods for black pepper are challenged by harmful residues or quality deterioration. Radiofrequency (RF) heating reduces the come-up time which allows to design a high-temperature short-time processing to inactivate Salmonella with minimal deterioration in product quality. The objectives of this study were to investigate RF heating for inactivation of Salmonella in whole black peppercorn and ground black pepper samples, evaluate Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella, and assess quality deterioration during RF heating of whole black peppercorn and ground black pepper samples. Both samples were inoculated with a 5-strain cocktail of Salmonella or E. faecium, equilibrated to the target water activity, and RF heated for 150 s for whole black peppercorn and 130 s for ground black pepper. Microbial stability and homogeneity tests were conducted for both Salmonella and E. faecium during moisture equilibration before RF heating to evaluate the inoculation method. Piperine, total phenolic and, volatile oil, and the antioxidant activity were assessed for the quality of both whole black peppercorn and ground black pepper samples. RF heating was demonstrated to provide 5.31 and 5.98 log CFU/g reduction of Salmonella for whole black peppercorn and ground black pepper, respectively. Whole black peppercorn and ground black pepper samples were dried to their optimal storage moisture after RF heating. The higher thermal resistance of E. faecium was observed during RF heating of both black pepper samples. The quality analysis showed that the quality of both black pepper samples did not experience a considerable change after RF heating. In this study, an applicable RF pasteurization process was developed for whole black peppercorn and ground black pepper, which provided effective inactivation of Salmonella while minimizing the quality deterioration. E. faecium was found to be a suitable surrogate for Salmonella during the RF heating of both whole black peppercorn and ground black pepper samples. Advisors: Jeyamkondan Subbiah & Jayne Stratto