Assessment of uniformity of microwave-based heating profiles generated by solid-state and magnetron systems using various shapes of test samples

Dinani, Somayeh Taghian; Hasić, Mersiha; Auer, Matthias; Kulozik, Ulrich

doi:10.1016/j.fbp.2020.08.013

Cited by 24 publications

(9 citation statements)

References 15 publications

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“…Overall, it can be concluded that the solid-state microwave system provides more uniform heating than the magnetron system in both vertical and horizontal orientations, especially at the H–ON orientation using the Maillard color changes. A higher uniformity of heating in the solid-state microwave system was found by our previous research investigating different positions [ 11 ], different sample shapes [ 16 ], and different frequencies [ 20 ]. Generally, uneven heating and formation of hot spots are famous problems for the heat processing of samples in the magnetron microwave system [ 2 ].…”

Section: Resultsmentioning

confidence: 90%

“…Moreover, shape [ 15 ], position, and orientation of the samples are factors to improve microwave heating uniformity [ 11 ]. In the paper by Taghian Dinani, Hasić, Auer, and Kulozik (2020) [ 16 ], we compared three different shapes of samples including spherical, cylindrical, and cuboid shapes. In this paper, the cuboid shape was suggested as the best, perfectly showing the changes of microwave field distribution.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Vertical and Horizontal Sample Orientations on Uniformity of Microwave Heating Produced by Magnetron and Solid-State Generators

Dinani

Jenn

Kulozik

2021

Foods

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In this study, the effect of different horizontal and vertical orientations of a model sample (cuboid gellan gel samples containing Maillard reactants) on microwave heat processing was investigated in the solid-state and magnetron microwave systems. To achieve this target, seven orientations inside both microwave cavities were defined. Two of the investigated sample orientations were in a vertical position with and without turntable rotation, and five in a horizontal position. Furthermore, samples at horizontal orientations were put at an angle position without turntable rotation. To analyze the microwave heating patterns, infrared (IR) pictures and photographs of the gellan gel samples were taken after processing to document IR-based thermal and Maillard color changes, respectively. Three main factors for improvement of the heating homogeneity were identified: first, processing samples in the solid-state microwave system; second, position variation of the sample by turntable activated; and third, horizontal orientation. In addition, it was observed that placing the gellan gel samples in a vertical position in the magnetron microwave system resulted in considerably more absorbed power and a more uniform microwave heat processing compared to other horizontal orientations in this system. This indicated a non-uniform microwave field distribution. The results of this study can also confirm the importance of designing suitable food packaging: a vertical shape for more microwave energy absorbance and thus, more energy efficiency, and a horizontal shape for more uniform microwave heat processing.

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Section: Resultsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Effect of Vertical and Horizontal Sample Orientations on Uniformity of Microwave Heating Produced by Magnetron and Solid-State Generators

Dinani

Jenn

Kulozik

2021

Foods

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“…B. Pandit, 2006;B. R. Pandit et al, 2007;Tang et al, 2007;Taghian Dinani, Kubbutat, et al, 2020;Taghian Dinani, Hasić, et al, 2020;Taghian Dinani, Feldmann, et al, 2021).…”

Section: Maillard Reactionmentioning

confidence: 99%

“…Mid‐sized geometries show hot spots between the center and the outer rim (Schubert et al., 1991). In terms of shape, spherical products show different temperature distribution than brick‐like products due to focusing and edging effects (Taghian Dinani, Hasić, et al., 2020). Processing variables such as microwave frequency, phase, power, product movement, number of microwave entrance ports, and location of ports have an impact on heat distribution in microwave applications.…”

Section: Introductionmentioning

confidence: 99%

Critical assessment of methods for measurement of temperature profiles and heat load history in microwave heating processes—A review

Kalinke

Kubbutat

Dinani

et al. 2022

Comp Rev Food Sci Food Safe

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Limitations of microwave processing due to inhomogeneities of power input and energy absorption have been widely described. Over‐ and underheated product areas influence reproducibility, product quality, and possibly safety. Although a broad range of methods is available for temperature measurement and evaluation of time/temperature effects, none of them is sufficiently able to detect temperature differences and thermally induced effects within the product caused by inhomogeneous heating. The purpose of this review is to critically assess different methods of temperature measurement for their suitability for different microwave applications, namely metallic temperature sensors, thermal imaging, pyrometer measurement, fiber optic sensors, microwave radiometry, magnetic resonance imaging, liquid crystal thermography, thermal paper, and biological and chemical time‐temperature indicators. These methods are evaluated according to their advantages and limitations, method characteristics, and potential interference with the electric field. Special attention is given to spatial resolution, accuracy, handling, and purpose of measurement, that is, development work or online production control. Differences of methods and examples of practical application and failure in microwave‐assisted food processing are discussed with a special focus on microwave pasteurization and microwave‐assisted drying. Based on this assessment, it is suggested that infrared cameras for measuring temperature distribution at the product surface and partially inside the product in combination with a chemical time/temperature indicator (e.g., Maillard reaction, generating heat‐induced color variations, depending on local energy absorption) appear to be the most appropriate system for future practical application in microwave food process control, microwave system development, and product design. Reliable detection of inhomogeneous heating is a prerequisite to counteracte inhomogeneity by a targeted adjustment of process and product parameters in microwave applications.

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“…Recent solutions have been proposed to reduce the non-uniformity of microwave heating in solid foods, such as movement along conveyor belts [6,7], use of turntables [8][9][10], use of water instead of air surrounding the food product [6,11], use of novel microwave generators [12][13][14][15], and use of alternative microwave frequencies [16,17]. However, the non-uniformity and complex heating patterns are still a challenge that requires detailed modelling of the field distribution in the cavity and food, as Knoerzer et al [4] and Dinani et al [15] stated.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Microwave Applicator Design on Electromagnetic Field Distribution and Heating Pattern of Cooked Peeled Shrimp

Siguemoto

Gut

Dimitrakis

et al. 2021

Foods

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Non-uniform temperature distribution within solid food is a major problem associated with microwave heating, which limits industrial applications. Therefore, an experimentally validated 3D model was proposed to study the effect of microwave applicator geometry on the electromagnetic field distribution and heating pattern of shrimp under different processing conditions. Simulation results were compared with physical experiments, in which a cooked peeled shrimp sample was heated using two different laboratory-scale microwave applicators (rectangular and cylindrical cavities). For the rectangular applicator, the temperature distribution within the shrimp, when examined in cross-section, was more homogeneous compared to that of the cylindrical applicator. The results showed the influence of the complex shape of the food on the temperature distribution during microwave heating, as well as of process parameters (input power and geometry cavity). Moreover, this modelling method could provide a better understanding of the microwave heating process and assist manufacturing companies to evaluate a suitable microwave applicator according to their specific purpose.

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Assessment of uniformity of microwave-based heating profiles generated by solid-state and magnetron systems using various shapes of test samples

Cited by 24 publications

References 15 publications

Effect of Vertical and Horizontal Sample Orientations on Uniformity of Microwave Heating Produced by Magnetron and Solid-State Generators

Effect of Vertical and Horizontal Sample Orientations on Uniformity of Microwave Heating Produced by Magnetron and Solid-State Generators

Critical assessment of methods for measurement of temperature profiles and heat load history in microwave heating processes—A review

Evaluation of Microwave Applicator Design on Electromagnetic Field Distribution and Heating Pattern of Cooked Peeled Shrimp

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