TOMATO PERICARP TISSUE RESONANCE AND ITS USE IN TEXTURE EVALUATION

The use of resonance properties, measured by dynamic oscillation using a constant stress rheometer, as textural parameters for excised peric arp tissue of tomato (Lycopersicon esculentum Mill cv Trust) fruit dur ing 21 days of ambient temperature ripening was assessed relative to t he large-deformation behavior measured by flat-plate compression. The resonance frequency (f(r)) of excised tissue discs decreased significa ntly (P < 0.05) over the first 9-12 days, and then approached a relati vely low and constant value with subsequent ripening. A significant (P < 0.05) increase in associated resonance strain amplitude (gamma(max) ) became apparent after the first 9-12 days of tomato fruit ripening. Ripening-associated changes in bioyield and failure strengths, toughne ss, and apparent elastic and failure deformability moduli derived from flat-plate compression tests were similar to those observed for tissu e f(r). Results were consistent with a change in the dominant mode of tissue failure from cell relaxation and rupture to debonding after 9-1 2 days of fruit ripening. A significant (P < 0.05) semilogarithmic rel ationship was observed between f(r), but not gamma(max) and compressio n parameters, allowing for reasonable prediction of large-deformation behavior on the basis of measurement of only fr. The results demonstra te that resonance frequency may provide a useful parameter in the eval uation of tomato pericarp tissue texture.