Sugar Determination in Grapes Using NIR Technology

In the last years, the interest in near infrared (NIR) technology is growing. Among the advantages offered by NIR spectroscopy are: speed, low cost, high repeatability, high reproducibility, and nondestructive. The purpose of this paper is to study the possibility of using NIR reflectance spectroscopy for correlation with sugar contents in grapes of the following varieties: Garnacha and Viura. These procedures were performance: fruits were hand-harvested and 30 grapes of each variety were selected. Mass, sugar and NIR (800-2500 nm) reflectance spectra of all the samples were obtained. The harvesting lasted long to obtain a wide range of the sugar content. Data were analysed using SPSS and SAS. It is possible a correlationship between NIR spectra and sugar (°Brix) so we can predict °Brix of grape with NIR technology. Multilinear Regressions were obtained. So, Viura multilinear regression used 33 variables (R² = 0,925; standard error of estimate = 1,0446) and Garnacha, 63 variables (R² = 0,89; standard error of estimate = 1,0508).