Fluorescence spectral study in grapes (Vitis Vinifera L.) Benitaka variety to different solid soluble values

The spectral images used as an alternative to the quality nondestructive evaluation, can contribute to improve monitoring and control of variables involved in partial dehydrated grapes for production of juice and / or wine, with the product quality as goal. This study aimed to differentiate Benitaka variety grapes with different concentrations of soluble solids using spectral image of fluorescence. The grape samples come from to Vale do São Francisco-State of Bahia, and were forwarded to the Laboratory of Atomic Interactions-Institute of Physics of São Carlos, University of São Paulo. The treatments consisted by two (T1 and T2) being T1-fresh grapes (12.54 +/- 0.09 °Brix), and T2-partial dehydrated grapes (in forced air oven at T=65°C and RH=50%) (13.32 +/- 0.08°Brix). The fluorescence image system used consists in a scientific CCD camera, lens system, a variable optical filter, and illumination system with LEDs (UV-405 nm). The wavelengths spectrum used in this study were between 480 to 750 nm. The spectral calibration occurred through a principal component analysis (PCA) in Matlab, wherein principal components which represent most the data were selected, separating T1 e T2. To select the best wavelength was applied a linear regression forward a PCA model to image data. After the PCA implementation was possible to distinguish the different soluble solids values in grapes to T1 and T2, setting the best wavelengths were to 480; 493; 552; 568; 605; 645; 666; 690 and 715 nm. The applied technique can contribute to technological advancement in the non-destructive evaluation field and real-time in high added value products such as derivatives Viticulture.