FUNDAMENTAL FRACTURE PROPERTIES ASSOCIATED WITH SENSORY HARDNESS OF BRITTLE SOLID FOODS

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ABSTRACTA series of biscuit‐like model foods that vary primarily in hardness, while keeping other sensory attributes less variable, was developed and used to investigate the relationship between fundamental fracture properties and the sensory perception of hardness of brittle solid foods. Fifteen biscuit samples were evaluated by both a trained sensory panel and three instrumental tests (three‐point bending test, single‐edge notched bend test and modified texture profile analysis), and their relationships were determined by simple linear regression analysis. Correlations revealed that the perceived hardness during biting or chewing is fracture related, and it is directly related to the amount of stress required to initiate and propagate a crack in a material (i.e., fracture stress [σ] and critical stress intensity factor [KIC], respectively). The fracturing of these hard and brittle biscuits appeared to be associated with the release of energy as sound, and thus, the perceived hardness and crunchiness were indistinguishable.PRACTICAL APPLICATIONSSensory evaluation is time consuming and expensive, and, therefore, reliable and practical (faster, less expensive and reproducible) instrumental methods are needed to accurately predict sensory texture attributes, at least, in the product development and quality control stages. This study demonstrated that the perceived hardness of biscuits can be tracked by σ and KIC with remarkable precision. These properties may be used as a reliable replacement for a sensory assessment of hardness in brittle solid foods, where applicable.