Texture of parenchymatous plant tissue: A comparison between tensile and other instrumental and sensory measurements of tissue strength and juiciness

The cellular basis of textural diversity in selected fruit and root tissue has been investigated using tensile measurements of tissue strength. The mechanism of tissue failure, either cell rupture or cell-to-cell debonding, was determined by examining the fracture surface using Low Temperature Scanning Electron Microscopy (LTSEM). Information provided by tensile measurements was compared with that provided by sensory and other instrumental measurements of tissue hardness and juiciness. Instrumental measurements included penetrometer, Kramer shear cell, apparent juice content, and juice release from a freshly cut surface. During tensile testing, the shape of the force-distance curve, along with maximum force and information on the cause of tissue failure were able to provide a comprehensive characterization of the texture. However, measurements of tensile strength, along with measurements of puncture strength and shear strength, showed a curvilinear relationship with sensory assessments of tissue hardness. This curvilinear relationship is fundamental to the psychophysical basis of human perception of texture. We speculate that the psychophysical laws that govern the relationship between mechanical hardness of a tissue and the associated sensory response may provide a major limitation to further improvements in the instrumental measurement of texture. We also discuss the use of instrumental measurements of juiciness to evaluate fruit quality. (C) 1997 Elsevier Science B.V.