ABSTRACTPenetration tests have been conducted on chewing gums of different ages and textures. Penetration forces were measured using 7 rods varying in diameter and at 2 testing speeds. The data were examined for fit to 2 different equations: (1) A model, previously given in the literature, which implies that the force of penetration is composed of shear components (proportional to rod diameter) and of compression components (proportional to the square of the rod diameter); (2) A model in which the penetration force consists of shear elements, as above, plus viscous components, proportional in this study to the 1.6th power of rod diameter. The observed data fit either model well; the equation postulating the presence of viscous deformation provides consistently, though not statistically, a superior fit. Penetration forces measured at low testing speed are consistently lower for corresponding samples and rods than those penetrated more rapidly, also suggestive of a viscosity component in the deformation process. The equation constants appear to be useful for characterizing chewing gum texture, responding sensibly to variations in the firmness of the material with age.
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