Evaluation of Stress-Relaxation in Fruit Tissue

During fruit softening, tissue texture characteristics may be documented by stress-relaxation analysis. Data were collected when a conical probe was inserted into tomato tissue to a prescribed depth. Five parameters were resolved during the load decay. By this method the elastic (firmness or softness) and viscous characteristics of the fruit tissue were identified. The initial load required to insert the probe into the fruit reflects tissue elasticity, while the two time-dependent parameters, one reflecting the initial response time and the other corresponding to the point when the tissue ceases to accommodate the imposed load, reflect tissue viscosity. The technique is also applicable for the measurement of processed materials, viz. canned tomatoes and paste, when modified probes are used.