page 5-8 (GOOD LUCK LABLAB) (copy)

Dielectric properties

-          are defined as a molecular property that is fundamental in all the materials that are capable of impending electron movement resulting in polarization within the material on expose to an external electric field. Are non-metallic and non-conducting materials which stores electrical charges

Electrical permittivity

-          one of the important dielectric properties, is 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

Dielectric constant

-          is related to the capacitance of a substance and its ability to store electrical energy. It is defined as the ratio of the electric permeability of the material to the electric permeability of free space, such as in a vacuum condition

Dielectric loss factor

-          is related to energy losses when the food is subjected to an alternating electrical field. It is a measure of the loss of energy in a dielectric material through conduction, slow polarization currents, and other dissipative phenomena

Electrical conductance and resistance of AB materials

-          have been used in the food industry for the rapid assessment of the current quality and storage potential in marketing these products

Electrical conductivity

-          has been very useful in the food industry, specifically in processes involving heating and freezing. Played a fundamental role in ohmic heating

Ohmic heating

-          electricity is transformed to thermal energy when an alternating current flows through food

Dielectric properties

-          of food materials play very important role in partially frozen material specifically in determining the rates and uniformity of heating in microwave thawing. Also important in the selection of proper packaging materials and cooking utensils, and in the design of microwave and radio frequency heating equipment

Penetration depth of energy

-          the distance at which the power drops 37% of its value in the material

Electromagnetic radiation

-          provides wide range of application in the processing of food materials in ways which depend on their unique properties

High energy radiation

-          can be utilized in sterilization of foods

2450 MHz

-          amount of hertz of most home microwave ovens

Drying

-          an important application of electromagnetic wave through microwave heating

Conventional drying

-          as water is removed, starting from the outside of a food piece, an insulating layer of dry, porous material is formed, which grows large as drying proceeds

Microwaves

-          have been applied to conventional drying as well as freeze drying

Microwave-assisted freeze drying

-          is faster than conventional freeze drying, which uses conductive heating by direct contact with a heated platen to speed dehydration

Various methods and mathematical models

-          are used to express and solve important electrical properties of AB materials, particularly food materials

Electrical conductivity

-          also known as specific conductance, the reciprocal of electrical resistivity, represents the material’s ability to conduct electrical current. It is a measure of electric current flows through a food of unit cross-sectional area A, unit length L, and resistance R

Electrical conductivity cell

-          it is used to measure the electrical conductivity of a food material

Electrical resistivity

-          is a fundamental property of a material that quantifies how strongly it resists electrical current

Two probe measurement

-          this is the simplest method of measuring resistivity. In this method, voltage drop V across the sample and current through the samples I are measured

Four probes measurements

-          the potential probe is the most widely used method for resistivity measurements on the low resistive samples. In this method, the potential drop is measured across two probes and distance between these probes D replaces the sample length L

Four probe method

-          can be used to determine the resistance of the single crystal as well as the bulk specimen also. This method can eliminate the effects of contact resistance between the sample and electrical contacts and therefore is most suitable for low and accurate resistance measurements

Four point probe method

-          has proven to be a convenient tool for the resistivity measurement of small size (of the order of mm) specimen. This method is applicable when the distance between the probes is small compared to the smallest dimension of the sample, and provided none of the probe is too close to an edge of the sample

Pauw Method

-          this is the method discussed by vander Pauw to measure resistivity of flat disc (pellet) of arbitrary shape without knowing the current pattern

Montgomery Method

-          the samples are obtained in power form, used for pellet study

Pulse probe method

-          also known as a modified dc method has reported by C.R.B. In this method, a short pulse of high voltage is applied to the sample and the current or the potential drop across a pair of probes of the sample is measured, usually by means of a fast oscilloscope or other amplifying and recording systems.

Lister

-          can also be used to determine the resistivity of some samples

Electrical Resistance

-          is a measure of its opposition to the flow of electric current.

Electrical Conductance

-          the reciprocal quantity of electrical resistance, and is the ease with which an electric current passes

ohm

-          SI unit for electrical resistance

Siemens (S)

-          Formerly called mho is the unit used to measure electrical conductance

Dielectric properties of biological materials

-          are important in the research on microwave processing of foods and agricultural materials, and the destruction of insect pests of postharvest and stored products. Are required to provide insight into the interaction between materials and microwave and radio frequency (RF) energy during microwave and RF heating.

Dielectric constant

-          is the ability of a material to store microwave energy

Dielectric loss factor

-          is the ability of a material to dissipate microwave energy into heat

Loss factor

-          The parameter that measures microwave absorptivity

Parameter

-          is necessary to indicate the distance that microwaves will penetrate into the material before it is reduced to a certain fraction of its initial value.

Power penetration depth

-          is the parameter which is defined as the depth at which power decreases to 1/e or (36.8%) of its original value.

Electromagnetic radiation

encompasses a wide variety of phenomena as represented by the various regions along its broad spectrum. Is classified by wavelength or frequency

Optical Properties

-          Are those properties resulting from physical phenomena occurring when any form of light interacts with the material under consideration. Are related to consumer judgment on food appearance and produce some kind of visual effect. Can be used to perform quality control and continuous inspection during processing operations. Are those material properties resulting from physical phenomena occurring when any form of light interacts with the material under consideration.

Color

-          Is the general name applied to all sensations arising from the activity of the retina, and is related to visual appearance of food including shape, size, surface and flesh structure, and defects. It is the characteristic of visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple. Is described in three ways: by its name, how pure or desaturated it is, and its value or lightness. Is a perceptual phenomenon that depends on the observer and the conditions in which the color is observed. Is a characteristic of light, which is measurable in terms of intensity and wavelength. Is the basis of optical sensors used in high speed sorting machines to separate and grade raw nuts, fresh fruit, processed vegetables, among others

Colorimeters

-          Used to measure color instrumentally, which may be broadly classified as tristimulus colorimeters and spectrophotometers. Are designed to measure only some parameters related to sensory colors. Are very useful in the quality control of foods, and give results normally correlated with visual measurements

Hue

-          Refers to the attribute of a visible light due to which it is differentiated from or similar to the primary colors: red, green and blue. Is also used to refer to colors that have no added tint or shade.

Chroma

-          Refers on how pure a hue is in relation to gray.

Saturation

-          Is the degree of purity of a hue.

Intensity

-          Is the brightness or dullness of a hue. One may lower the intensity by adding white or black.

Luminance or value

-          Is a measure of the amount of light reflected from a hue. Those hues with a high content of white have a higher luminance or value.

Shade and tint

-          Are terms that refer to a variation of a hue.

Spectrophotometers

-          The former measures intensity of light through the completely visible spectrum

Munsell calorimeter

- Consists of a circular rotating platform where several colored disks are mixed in different proportions to provide a range of shades to match the color of a certain food product. It is widely used in the food industry for quality control of a number of solid products like tomatoes, fruits, and peanut butter

Tristimulus colorimeters

-          measure both related scales of Munster, Hunter, or CIE systems, which are numerically related.

Color contrast

-          is the difference in light between font and its background.

Color contrast ratio

-          Is the numerical value assigned to the difference in light between the foreground and the background.

Contrast

-          The difference in visual properties that makes an object (or its representation in an image) distinguishable from other objects and the background. Is the perceived difference in colors that are in close proximity to each other.

Intensity

-          Is also referred to as saturation or chroma, refers to the degree of purity of a color. Is the purity or saturation of a color

Bright

-          a highly intense color

More neutral or muted

-          low-intensity color

Color's Intensity

-          Always diminishes when it gets mixed with another color.

Glossmeters

-          Measure intensity of light reflected at three angles of incidence and reflection, and normally give results in the form of indices, obtained by comparing the sample reflectance to that of a highly reflective flat glass, used as a calibration standard.

Light transmittance

-Is a property of transparent and translucent materials, measuring their capacity to transmit light all the way through themselves

Opaque materials

-          Have a transmittance of zero as no light at all gets through.

Transmission

-          Occurs when light or electromagnetic energy passes into a material and some measurable amount is able to pass out the  other side

Transmittance

-          Of an object or instance of material measures its effective transmission, given as a ratio of the total amount of light or electromagnetic radiation that is transmitted compared to the total amount incident upon it.

Transmissivity

-          Of a material is a measure of its ability to transmit light or radiation.

Most foods

-          Are opaque; they do not allow energy to be transmitted through them, thus most energy is absorbed or reflected. 

Energy

-          Is reflected at various wavelengths each representing a different color to the human eye

Light absorptance

-          Is a measure of material’s capacity to absorb light that is incident upon it or passing through it

Opaque Materials

-          Light absorptance is very high and directly related to surface color, with black as highest and white the least

Transparent Materials

-          Light absorbance is very low and affects the transmitted component only as it passes through.

Absorption

-           Is the process by which electromagnetic radiation is converted to another type of energy as it passes through a material

Absorptance

-          of a particular object or instance of material measures its effective absorption, given as a ratio of the total amount of light or electromagnetic radiation that is absorbed compared to the total amount originally incident upon it. Is measured as the ratio of the total amount of light or electromagnetic radiation that is absorbed compared to the total amount originally incident upon it. Is a dimensionless fractional value between 0 and 1

Absorptivity

-          of a material is the amount of absorption that takes place per unit of distance light travels within it.

Vacuum

-          Is the closest, we can ever come a material with an absorptance of 0, no real material other than perhaps a cosmic black hole has an absorptance of 1.

Light reflectance

-          Is a measure of the ability of a surface to reflect light or other electromagnetic radiation. It is equal to the ratio of the reflected flux to the incident flux. It can be also measured as the ratio of the total amount of radiation reflected by a surface to the total amount of radiation incident on the surface.

Translucency

-          Can be the measurement of the reflection of a thin sample against both a white and black background.

The value of reflection from an Opaque Layer

-          Is calculated as a ratio between absorption and scattering to measure scattered light.

Continuous color measurements

-          Are used in tasks involving color sorting, or electronic sorting, by using in-line systems.

Optical sensors

-          Are extremely fast and allow sorting decisions to be made in less than 0.1 sec.

Color sorting machines

-          Are able to sense and remove off color objects to provide a similar colored acceptable product that is clear of foreign matter.

Machine vision

-          Has advanced from the use of noncolor, such as grey-level, to use of three-component RGB color

Color measurement techniques

-          Are used for recording desirable color changes in canning salmon with higher oil content, defining translucency of the tissues and green pigment degradation after blanching treatment of green peas, studying browning kinetics, or determining the influence of particle sizes in the final color of powders. Can improve the understanding on processing changes and reaction kinetics in foods. Are used for recording desirable color changes in canning salmon with higher oil content, defining translucency of the tissues and green pigment degradation after blanching treatment of green peas, studying browning kinetics, or determining the influence of particle sizes in the final color of powders.

Color sorting

-          Is used for a very wide range of food materials in screening defects

Visible, infrared, and ultraviolet beams

-          Can provide continuous inspection through scanning of product size, symmetry, damage, irregular shape, fill level, and label placement by adding automatic software in connection with mechanical devices

The human perception of color

-          Is important in marketing most products including foods.

4 to 8 ×10-7 m

-          The visible portion of the electromagnetic spectrum is that part which lies approximately in the wavelength range. Light energy in this range incident on biological materials is either transmitted, absorbed, or reflected.

622-780 nm range

-          In Electromagnetic energy this range is recognized as red

492-577 nm range

Is green, among others.

Glossiness

-          of a product is a property of the smoothness of its surface

Translucency

-          Is also worth consideration in some liquid foods, such as fruit juices. Its measurement can be determined by considering the contributions of both absorbed and scattered light when traversing these products. For a few clear liquid foods, such as oils and beverages, color is mainly a matter of transmission of light.

Gloss

-          Is the name given to light specularly reflected from a plain smooth surface. It can be defined by a goniophotometric curve, which represents the intensity of light reflected at the surface at different angles of incidence and viewing.

Translucency of foods

-          Is defined using an opaque-to-transparent scale. In liquid foods, light passing through changes its path randomly (in other words, is scattered) when interacting with suspended particles. Its measurement can be determined by considering the contributions of both absorbed and scattered light when traversing these products.

Translucency

-          Can be the measurement of the reflection of a thin sample against both a white and black background.

CIE, Munsell, Hunter, and Lovibond systems. 

-          The most use system of color analysis

CIE System

-          Spectral curves indicate how the eyes of normal observers respond to various spectral light types in the visible portion of the spectrum. The system is based on the fact that any color can be matched as a suitable mixture of red, green, and blue, known as tristimulus values of color.

Chromacity diagram

-          Defines different color points that define the standard color of a food.

Munsell system

-          all colors are described by three attributes: hue (or type of color), lightness (relative to the proportion of light emitted), and saturation or purity (associated with clear to dark perception).

Hue scale

-          Is based on ten hues distributed on a circumference (scaled 1 to 10); the lightness ranges from black to white (0 to 10) and is distributed on a perpendicular line; the purity is of irregular length beginning with 0 for the central gray to the limit of purity obtainable by available pigments in the Munsell book of color.

The Hunter system

-          Also a three-dimensional system using parameters L*, a* , and b* in each dimension: L* is the lightness (nonlinear), a* is redness or greenness