Interdisciplinary Modules to Teach Waste or Residue Management in the Food Chain
MODULE 2: IDENTIFICATION, QUANTIFICATION, AND CHARACTERIZATION OF WASTES/RESIDUES
CHARACTERIZATION
Physical Characteristics
The physical characteristics of a food product can be measured by:
Temperature. Use a thermometer.
pH. Use a bench-top or hand-held pH meter.
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AOAC Method no. 973.41 for pH of water (AOAC, 2000).
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AOAC Method no. 945.42 for pH of bread (AOAC, 2000).
Particle size. The size of the component materials in solid wastes is considered an important characteristic in the recovery of materials (Theodore & Theodore, 1996).
The size of the waste component can be computed using length, height, or width (Theodore & Theodore, 1996). See Appendix 2D for the formula.
The ASAE standard 319.3 JUL 97 (ASAE, 2000) recommends that the size of dry particulates be reported as geometric mean diameter and geometric standard deviation by mass. See Appendix 2D for the formula.
Density. Density is the unit mass per unit volume (Rahman, 1995).
True density. True density is the density of a pure substance or a material calculated from its components. This characteristic is not commonly used for wastes/residues (Rahman, 1995).
Bulk density. Bulk density is the density of a material when packed or stacked in bulk. The units of density depend on the units used for mass and bulk volume and should relate the weight to the volume the material occupies (Rahman, 1995).
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A common measurement method is the use of a specific gravity cup and an electronic balance. The specific gravity cup which has a known mass and volume is filled completely with the sample material, the lid is placed on the cup, excess sample material is removed, and the filled cup is then weighed on the balance (Rosentrater et al., 1999).
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A pycnometer is a device used to measure the density of a liquid.
Texture and rheology. Viscosity can be measured using a viscometer. The measurement is determined by the length of time required for a fixed quantity of fluid to pass or flow through a tube or capillary (Rao & Rizvi, 1986).
The two instruments frequently used to measure the texture of a food product include a texture analyzer and the Instron. Attachments for the texture analyzer can be used to measure specific characteristics such as the tenderness of meat and firmness of a semi – solid food such as a thick pudding and gels. Some researchers develop a texture profile analysis of food products being tested.
The Food Machinery Corporation Pea Tenderometer is used to measure the quality and maturity of fresh green peas (Rao & Rizvi, 1986).
The penetrometer is used to measure the firmness or yield point of semisolid foods such as thick pudding and gels (Rao & Rizvi, 1986)
Color. The Hunter Colorimeter (Model LabScan SN-12414, Hunter Associate Laboratory, Inc., Reston, Va.) and the L-a-b opposable color scales can measure the color of each product sample (Rosentrater et al., 1999).
Specific gravity. "Specific gravity is a measure of the density of a substance, liquid, or solid, in comparison to that of water at a specified temperature. The
specific gravity of pure water is defined as 1,000 at 10°C (50°F). One milliliter of distilled water weighs 1g at this temperature, or 100ml of water weighs 100g. A substance that is heavier than water will have a greater density and a higher specific gravity. When, for instance, 100ml of a liquid weighs 105g, then its specific gravity is 1,050 (105/100)"
(Smith,
Cash, Nip, & Hui, 1997, p256).
Some of figures, tables, and appendixes are in PDF format.
If you do not have a PDF reader, you can download the Adobe version from the Acrobat Download Page.
Introduction | General Characterization | Identification | Quantification | Characterization | References
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