Comparison of multispectral indexes extracted from hyperspectral images for the assessment of fruit ripening

The present research is focused on the application of artificial vision to assess the ripening of red skinned soft-flesh peach ('Richlady'). Artificial vision allows a spatially detailed determination of the ripening stage of the fruit. The considered optical indexes (Ind(1) and Ind(2), proposed in the present research, and Ind(3) and I-AD. Proposed by other authors) are based on the combination of wavelengths close to the chlorophyll absorption peak at 680 nm. Ind(1) corresponds approximately to the depth of the absorption peak, and Ind(2) corresponds to the relative absorption peak. An artificial image of each index was obtained by computing the corresponding reflectance images, which were acquired with a hyperspectral camera. All indexes were able to correct convexity (except for the just-harvested peaches and for Ind(1)). Ind(2) is the preferred index; it showed the highest discriminating power between ripening stages and no influence of convexity. Ind(2) also allowed the differentiation of ripening regions within the fruits, and it showed the evolution of those regions during ripening. (C) 2011 Elsevier Ltd. All rights reserved.