electrical properties of food materialss

properties of food

1. WELCOME 1

2. PRESENTATION ON ELECTRICAL PROPERTIES OF FOODS BY K.CH.S.SAIKIRAN I.M.TECH(FPE) 2

3. OVER VIEW OF PRESENTATION INTRODUCTION OF ELECTRICAL PROPERTIES DEFINITIONS APPLICATIONS INTRODUCTION OF DIELECTRIC PROPERTIES DEFINITIONS APPLICATIONS 3

4. ELECTRICAL PROPERTIES Non-destructive systems are recent trends for quality evaluation of fruits and vegetables. Information on post-harvest variations in electrical properties is needed to develop new instruments for this purpose Electrical properties are important when processing foods involving electric fields, electric current conduction, or heating through electromagnetic waves 4

5. DIFFERENT ELECTRICAL PROPERTIES RESISTANCE ELECTRICAL CONDUCTIVITY CONDUCTANCE 5

6. RESISTANCE The resistance of any material with a uniform cross-sectional area is determined by the following factors: Material Length Cross-sectional Area Temperature 6

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8. ELECRICAL CONDUCTIVITY Electrical conductivity is a measure of how well electric current flows through a food of unit cross-sectional area A, unit length L, and resistance R . It is the inverse value of electrical resistivity (measure of resistance to electric flow) and is expressed in SI units S/m in the following relation: σ = L /( AR) 8

9. MEASUREMENT OF ELECTRICAL CONDUCTIVITY The conductivity of a material is generally measured by passing a known current at constant voltage through a known volume of the material and by determining resistance . The total conductivity is then calculated simply by taking the inverse of the total resistivity. Basic measurements involve bridge networks (such as the Wheatstone bridge circuit) or a galvanometer. There are other devices that measure electrical conductivity of foods under ohmic or conventional heating conditions, using thermocouples and voltage and current transducers to measure voltage across and current through the samples 9

10. CONDUCTANCE The reciprocal of resistance is conductance (G), measured in siemens (S ) G = 1/R ( siemens, S ) 10

11. APPLICATIONS Electrical properties are important in processing foods with pulsed electric fields, ohmic heating, induction heating, radio frequency, and microwave heating. Conductivity plays a fundamental role in ohmic heating, in which electricity is transformed to thermal energy when an alternating current ( a.c .) flows through food. So it has potential to use in fluid pasteurization, it is important to know the effective conductivity or the overall resistance of liquid-particle mixtures 11

12. Furthermore , liquid-particle mixtures can be pasteurized using pulsed electric field technology, where products with low electrical conductivity are better and more energy-efficient to process. Electrical conductivity can be used for acidity studies, therefore, and for monitoring processes where acidity increases, as in fermentations . Crystallization processes (for example, in sugar solutions) can also be monitored with conductivity measurements, as conductivity has been found inversely proportional to viscosity, which in turn follows supersaturation closely . Conductivity measurements have also been used to measure moisture contents in materials, particularly grain products . 12

13. DIELECTRIC PROPERTIES Dielectric properties of food materials are those electrical properties which measure the interaction of food with electromagnetic fields Relative permittivity, dielectric loss factor, loss tangent and the alternate current conductivity are of concern in heating, drying and storage of grains . However, the first dielectric properties for grain were not reported until 45 years ago. 13

14. Electrical permittivity is a dielectric property 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. In solids, liquid, and gases the permittivity depends on two values: • T he dielectric constant ε’, related to the capacitance of a substance and its ability to store electrical energy; and • T he dielectric loss factor ε”, related to energy losses when the food is subjected to an alternating electrical field 14

15. Factors affecting the dielectric properties Frequency of the applied alternating electric field moisture content bulk density, temperature ionic nature, concentration (density ) structure and constituents of food materials 15

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19. APPLICATIONS Food grains Use of dielectric properties of grain for moisture measurement has been the most prominent agricultural application . The dielectric properties of cereal grains and oilseeds are essential for understanding their electric behaviour, and the development of indirect non-destructive methods for determining their physical properties. Fruits and vegetables Microwave permittivities , or dielectric properties of fresh fruits and vegetables have been considered for potential use in non-destructive sensing of quality factors, such as maturity in peaches and chilling injury in sweet potatoe 19

20. Livestock and fishery produce The dielectric technique can be used as an easy, rapid and accurate method for the assessment of quality parameters of fish, seafood and meat The dielectric method for freshness assessment of meat has several advantages: it is non-destructive, easy, rapid, effective, reliable and practical. Measurement of various meats and fish, including raw beef, pork, beef and pork fat, codfish, and herring at radio frequencies from 10 to 100 MHz Dielectric properties of codfish were measured at frequencies from 10 to 200 MHz at temperatures from −25 to 10°C 20

21. THANK U 21