TEXTURE OF PARENCHYMATOUS PLANT-TISSUE - A COMPARISON BETWEEN TENSILEAND OTHER INSTRUMENTAL AND SENSORY MEASUREMENTS OF TISSUE STRENGTH AND JUICINESS

The cellular basis of textural diversity in selected fruit and root ti ssue has been investigated using tensile measurements of tissue streng th. The mechanism of tissue failure, either cell rupture or cell-to-ce ll debonding, was determined by examining the fracture surface using L ow Temperature Scanning Electron Microscopy (LTSEM). Information provi ded 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, a pparent juice content, and juice release from a freshly cut surface. D uring tensile testing, the shape of the force-distance curve, along wi th maximum force and information on the cause of tissue failure were a ble to provide a comprehensive characterization of the texture. Howeve r, measurements of tensile strength, along with measurements of punctu re 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 tex ture. We speculate that the psychophysical laws that govern the relati onship between mechanical hardness of a tissue and the associated sens ory response may provide a major limitation to further improvements in the instrumental measurement of texture. We also discuss the use of i nstrumental measurements of juiciness to evaluate fruit quality. (C) 1 997 Elsevier Science B.V.