The aim of this study was to estimate the adhesive and cohesive fracture energies, and frictional characteristics of 7 types of cooked starch and flour sheets and combine these into a model framework for textural analysis. Cutting tests with wires of diameter 0.30 to 0.89 mm were performed with and without lubrication. Plots of the work done, normalized to the area cut by the wire, showed that this to be linearly related to wire diameter irrespective of lubrication. The oil had little impact on the intercept of these plots, giving cohesive fracture energy (Gc ) ranges for these foods between 6.8 and 32.5 J/m(2) . However, lubrication had a strong influence on the slope of the plots. From a comparison of the slopes for lubricated versus unlubricated tests, the kinetic coefficient of friction μkcould be calculated. Values for μk between 0.007 and 0.521 for different foods were obtained. Peeling tests were performed by lifting sheets vertically away from a fresh mica surface. The adhesive fracture energy Ga , varied from 2.5 to 4.8 J/m(2) . The results can be modeled by plotting the ratio of cohesive to adhesive fracture energy against the coefficient of friction. Thresholds in both axes suggest a physical basis for distinguishing textural perceptions. However, sensory testing with 12 subjects using the 7 food types could not establish whether this framework, however well-established physically, would apply to oral sensations. A much larger test would be required.
Keywords: adhesion fracture energy; cohesion; noodle sheet; peeling test; wire cutting.
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