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Compression Test of Food Materials of Convex Shape
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgASAE ASAE S368.4 December 2000
Keywords: Compression, Food, Test
1 Purpose and Scope
1.1 This Standard is intended for use in determining mechanical attributes of food texture, resistance to mechanical injury as a result of static loading, and quasi-static force-deformation behavior of food materials of convex shape, such as fruits and vegetables, seeds and grains, and manufactured food materials.
1.2 Compression tests of intact biological materials provide an objective method for determining mechanical properties significant in quality evaluation and control and maximum allowable static load for minimizing mechanical damage. The results apply to quasi-static loading rather than impact loading. The equations given are adapted from the theory of contact between convex surfaces made of elastic materials. Most food and biological materials exhibit non-linear behavior at larger (e.g., 5% strain or greater) deformations. Furthermore, to completely characterize the material, a study of its viscoelastic behavior is needed. However, these simplified tests give information that can be used to quantitatively determine the differences caused by factors such as variety, drying temperature, storage technique, maturity, and processing technique. The applicability of the analysis can be validated by plotting the log of applied force as a function of the log of deformation. If the equations are valid, the slope of the line should be 1.5 (Fridley et al., 1968; Arnold and Mohsenin, 1971).
1.3 Compression tests on food materials are routinely conducted using fully automatic test equipment such as the Instron Universal Testing apparatus. Factors such as sample conditioning prior to testing, loading geometry, and loading rate can influence the results of such tests. Therefore, it is desirable to standardize testing and reporting procedures so that data from various sources can be more easily compared.
1.4 Determination of compressive properties requires the production of a complete force-deformation curve. From the force-deformation curve, stiffness; apparent modulus of elasticity; toughness; force and deformation to points of inflection, to bioyield, and to rupture; work to point of inflection, to bioyield, and to rupture, and maximum normal contact stress at low levels of deformation can be obtained. Any number of these mechanical properties can, by agreement, be chosen for the purpose of evaluation and control of quality.(Download PDF) (Export to EndNotes)