Analysis of the sharpness of blades for food cutting

Although the sharpness of a blade is responsible for cutting performance, there is no single and unambiguous literature definition of sharpness. The blade sharpness index (BSI) proposed by McCarthy et al. (Engineering Fracture Mechanics 74, 2205–2224, 2007) is a dimensionless number, derived from different cutting properties, to classify the sharpness of thin blades such as scalpels. In this study we transfer the BSI concept to blades with geometries typical in food cutting applications. After a series of cutting experiments at two velocities with blades that differed in wedge angle and abrasion state and by using three elastomers as substrate, we identified that the BSI can be regarded as a linear function of blade tip radius and force at cut initiation. The BSI was independent of cutting velocity, cutting substrate and wedge angle. Subsequently, cutting of foods with differently blunted blades revealed a specific impact on cutting performance, which depended on the food properties. Thus the BSI concept itself is helpful to classify the blade state, but it is less sufficient to evaluate the suitability of a knife with respect to a particular cutting application. •Sharpness of blades for food processing is analyzed with different concepts.•The blade sharpness index is compared with optical and mechanical sharpness measures.•The blade sharpness index only depends on the blade tip radius.•Force at cut initiation provides an adequate and simple sharpness measure.•Sharpness alone can be insufficient to evaluate cutting performance of certain foods.