BEHAVIOR OF DIFFERENT FOODS IN THE STANDARD SHEAR COMPRESSION CELL OF THE SHEAR PRESS AND THE EFFECT OF SAMPLE WEIGHT ON PEAK AREA AND MAXIMUM FORCE

Abstract

Twenty-four foods (encompassing fruits, vegetables, meat, bread, cheese and rice) were tested in the Allo Kramer Shear Press at various weight levels ranging from those needed to cover the bottom of the cell to those required for a complete fill. The relationship between maximum force values and sample weight was found to be different for different foods. Products could be grouped into three general categories: those exhibiting a constant force to weight ratio (e.g. white bread, sponge cake), those exhibiting a continuously decreasing force to weight ratio (e.g. raw apples, cooked white beans), and those exhibiting a constant force, independent of sample weight, beyond a certain cell fill level (e.g. canned beets, canned and frozen peas). Fitting the observed behavior into mathematical models allows to infer that extrusion, in addition to the previously recognized shear and compression, plays an important role in the behavior of foods in the standard cell of the Shear Press, and that most foods are subject to various combinations of these forces. The contribution of extrusion was confirmed by actual extrusion tests. Peak areas showed an exponential relationship to sample weight following the equation A = l0^a W^b . Some evidence was obtained that exponents a and b are related to the amount and the general type of resistance offered by the food.