Use of laser-scattering imaging to study tomato-fruit quality in relation to acoustic and compression measurements

A 670nm, 3 mW solid-state laser diode module has been used as light source to monitor quality changes of tomatoes (c.v. Trust) stored at room temperat ure for 8 days. The scattering images were captured and the total number of pixels in the image was taken as an indicator of fruit ripeness. Non-destr uctive acoustic and traditional compression tests were used to determine th e firmness of tomatoes. The results showed significant differences in image size (number of pixels) for tomatoes at different maturity stages. The ima ge size increased during the storage period. Fruit firmness showed a negati ve correlation with the image size. The soft tomato corresponds to a larger image size. A second order polynomial equation expressed the relationship between the stiffness factor and the size of scattering image (r(2) approxi mate to 0.62). The system has the potential to be used to evaluate the ripe ness of tomato fruits.