Dielectric Properties Of Food Materials Research Articles

Use of Modern Regression Analysis in the Dielectric Properties of Foods.

The dielectric properties of food materials is used to describe the interaction of foods with electromagnetic energy for food technology and engineering. To quantify the relationship between dielectric properties and influencing factors, regression analysis is used in our study. Many linear or polynomial regression equations are proposed. However, the basic assumption of the regression analysis is that data with a normal distribution and constant variance are not checked. This study uses sixteen datasets from the literature to derive the equations for dielectric properties. The dependent variables are the dielectric constant and the loss factor. The independent variables are the frequency, temperature, and moisture content. The dependent variables and frequency terms are transformed for regression analysis. The effect of other qualitative factors, such as treatment method and the position of subjects on dielectric properties, are determined using categorical testing. Then, the regression equations can be used to determine which influencing factors are important and which are not. The method can be used for other datasets of dielectric properties to classify influencing factors, including quantitative and qualitative variables.

Review on the Study of Dielectric Properties of Food Materials

Dielectric properties of foods are used to explain interactions of foods with electric fields. It determines the interaction of electromagnetic waves with matter and defines the charge density under an electric field. For engineering point of view, dielectric properties are the foremost important physical properties related to radio frequency and microwave heating, it is critical to possess knowledge of the dielectric properties of materials in products and process development and, within the modern design of dielectric heating system for the need of desired process. Dielectric properties are often categorized into two: dielectric constant and dielectric loss factor. Dielectric constant is the ability of a material to store microwave energy and dielectric loss factor is the ability of a material to dissipate microwave energy into heat. Dielectric properties of food materials are required for various applications in food industry like microwave (at 915 or 2450 MHz), radio wave (at 13.56, 27.12 or 40.68 MHz) and magnetic field processing. In this review, the dielectric properties of various food groups were listed such as; Cereal grains and oilseeds, Bakery product, Dairy products, Poultry products, Fruits and vegetables. Dielectric properties are utilized in fruit drying processes, protect food materials from insects that already present in dried fruits, pasteurization, sterilization, tempering of concentration of liquid foods such as fruit juices, identification, processing, quality monitoring of fats and oils and improvement during oil processing and storage. The dielectric studies of food materials are an important tool to identify the quality of food materials and to improve dielectric heating uniformity. Frequency, moisture content, phase change, storage time and temperature are main factors that influence the dielectric properties of food material.

Dielectric Properties of Foods

Dielectric properties of materials are used for evaluating their interactions with electromagnetic energy. Dielectric properties of food materials are required for various applications in food industry such as microwave (at 915 or 2450 MHz), radio wave (at 13.56, 27.12 or 40.68 MHz) and magnetic field processing. In order to understand the response of food materials to electromagnetic energy, dielectric parameters must be determined as a function of frequency, temperature, composition and moisture content. In this review, the dielectric properties of different food groups were listed depending on temperature and frequency ranges. In addition to the literature data of dielectric properties, the penetration depths of microwave or radio wave through food groups were calculated. The effects of temperature and composition (mostly moisture content) on dielectric properties depend on the type of the food and sometimes on frequency. However, the effect of frequency is constant; increased frequency decreased dielectric constant, loss factor and penetration depth. The lowest calculated penetration depth belonged to the fish surimi gel as 3.39 mm at microwave frequency whereas they were high generally for fats, oily seeds and flours (max was 372602 mm for corn flour). It appears that dielectric properties of foods should be investigated further depending on the interactions between frequency, temperature and composition. And then, dielectric heating based on the aim of the process can be applied accordingly. Besides, it appears that the moisture content and especially the dipole rotation and the conductivity movements of the molecules in free water content of the food are some of the most critical factors influencing the dielectric properties of food materials.

Estimation of Dielectric Properties of Food Materials During Microwave Tempering and Heating

The present study concerns the estimation of the dielectric properties of both frozen and defrosted materials during a microwave tempering and heating process. A continuous wave at 2.45 GHz is fed into a rectangular waveguide and the sample, made of methylcellulose gel, fills the whole cross-section of the guide. Temperatures are detected within both frozen and defrosted samples during the heating treatment. The experimental temperatures are compared to the results obtained with a 2D finite element model, using the COMSOL® 4.2 software. The dielectric properties of the sample are estimated from the local temperature changes during the microwave tempering. For the defrosted zone, the estimation is compared to dielectric properties measurements with the open-ended coaxial probe. The results show good correspondence between experimental and simulated data. The uncertainties of the estimated permittivity and loss factors are also evaluated with a good accuracy for the frozen and defrosted phases. The estimation procedure is thus a promising tool in order to avoid complex experimental measurements of dielectric properties.

Influence of Water Content on RF and Microwave Dielectric Behavior of Foods

The importance of dielectric properties of food materials is discussed with respect to their influence on the geating of materials by radio-frequency and microwave energy and their use for rapid, nondestructive sensing of quality characteristics of such materials. Data are presented graphically showing the frequency and temperature of the dielectric consant and loss factor of wheat, fresh chicken breast meat, serveral fresh fruits, and apple juice, representing food materials with a wide range of moisture content. The influence of moisture or water content on the dielectric behavior of these materials is discussed, and that vehavior is explanied in terms of dipolar relaxation and ionic conduction.

Measuring frequency- and temperature-dependent permittivities of food materials

The permittivities or dielectric properties of food materials are of vital importance in understanding the behavior of these materials when they are exposed to electromagnetic fields in the process of microwave cooking or in other processes involving RF or microwave dielectric heating. Understanding these properties is also important in quality sensing by RF and microwave instruments. The most prominent example is instruments designed for rapidly sensing or measuring the moisture content of cereal grains and other food materials. An open-ended coaxial-line probe was used with sample temperature control equipment, designed for use with the probe, to measure permittivities of some liquid, semisolid, and pulverized food materials as a function of frequency and temperature. Graphical data for the dielectric constant and loss factor of homogenized macaroni and cheese, ground whole-wheat flour, and apple juice illustrate the diverse frequency- and temperature-dependent behavior of food materials, and the need for measurements when reliable permittivity data, are required. The materials were selected because interest had been expressed by others in their dielectric properties.

FREQUENCY AND TEMPERATURE DEPENDENCE OF THE DIELECTRIC PROPERTIES OF FOOD MATERIALS

An open–ended coaxial–line probe was used with network and impedance analyzers and a sample temperature control assembly, designed for use with the probe, to measure the dielectric properties of some food materials as a function of frequency and temperature. Graphical data for the dielectric constant and loss factor of a macaroni and cheese dinner preparation, whey protein gel, ground whole–wheat flour, and apple juice illustrate the diverse frequency– and temperature–dependent behavior of the dielectric properties of food materials.

Electrical and dielectric properties of food materials. A bibliography and tabulated data. Zusammengestellt von M. Kent. 135 Seiten. Science and Technology Publishers, Hornchierch, Essex, England, 1987. Preis: 20,00 £

Food / NahrungVolume 32, Issue 4 p. 356-356 Rezensionen Electrical and dielectric properties of food materials. A bibliography and tabulated data. Zusammengestellt von M. Kent. 135 Seiten. Science and Technology Publishers, Hornchierch, Essex, England, 1987. Preis: 20,00 £ B. Gassmann, B. GassmannSearch for more papers by this author B. Gassmann, B. GassmannSearch for more papers by this author First published: 1988 https://doi.org/10.1002/food.19880320413AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume32, Issue41988Pages 356-356 RelatedInformation