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Development and Growth Regulation

Novel Technique for Measuring Tissue Firmness within Tomato (Lycopersicon esculentum Mill.) Fruit ¹

Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Hiroshima 730, Japan, Laboratory of Biology, Tezukayama College, Gakuen-minami, Nara 631, Japan, Department of Vegetable Crops, University of California, Davis, California 95616

Developmental changes of tomato (Lycopersicon esculentum) fruit tissues during maturation were analyzed by a physically defined method (stress-relaxation analysis). The tip of a conical probe connected to a load sensor was positioned on the cut surface of a sliced tomato fruit, and the decay of the imposed stress was monitored. Stress-relaxation data thus obtained were used for the calculation of three stress-relaxation parameters. Different zones within tomato fruit harvested at six different ripening stages were analyzed. One of the stress-relaxation parameters, minimum stress-relaxation time (T₀), decreased as the fruits matured. The decrease in T₀ was first found in the core of the carpel junction within the endopericarp at the blossom end during the breaker stage. The decrease in T₀ progressed from the blossom end, through the equatorial region and finally throughout the shoulder, as the fruit matured. In mature green fruit, T₀ values within the placenta and the proximal carpel junction were lower than those by other parts of the fruit. For all measurements the maximum stress-relaxation time was not substantially changed during maturation, nor were their changes observed in different regions of the fruit. The observed relaxation rate was therefore correlated with softening. The results indicate that fruit softening may be physically associated with the stress-relaxation parameter, T₀, and the extent of softening is a function of position within the fruit. Decreases in T₀ value appear to be correlated with the reported regional variation in the appearance of polygalacturonase.

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				G.O. S. Quiroga and A.A. Fraschina Evaluacion de atributos sensoriales y parametros bioquimicos en frutos de tomate transgenico con reducida actividad de poligalacturonasa / Evaluation of sensory attributes and biochemical parameters in transgenic tomato fruit with reduced polygalacturonase activity Food Science and Technology International, January 1, 1997; 3(2): 93 - 102. [Abstract] [PDF]