Optical detection of mealiness in apples by laser TDRS

Mealiness is a quality-impairing textural disorder, combining softness and absence of free juiciness. The only current test is destructive; it combines information from a mechanical probe test to classify the samples according to instrumental mealiness. Time-domain laser reflectance spectroscopy (TDRS) can assess simultaneously and independently the absorption of the light inside the irradiated body (mua coefficient) and the scattering of the photons across the tissues(-)mu 's, transport scattering coeff.) at each wavelength. With VIS and NIR lasers as light sources, TDRS was applied to Golden Delicious and Cox's apples (n=90), forming batches of untreated and storage-treated (20 degreesC & 95%RH) samples to induce mealiness. The collected data were clustered into groups according to their instrumental mealiness values. Three to seven optical coefficients were used as independent variables,when building discriminant functions, which correctly identified 75-89% of mealy apples.