Maturity, Variety and Origin Determination in White Grapes (Vitis Vinifera L.) Using near Infrared Reflectance Technology

Abstract

Soluble solids content, variety and origin of grapes are three relevant features to determine wine quality. Soluble solids content is directly related to ripeness. The capacity to certify the origin or variety of a grape is of major interest for wine makers. The aim of this paper was to study whether near infrared refl ectance (NIR) spectroscopy could be used to determine soluble solids content and to identify different varieties and origins of grapes. Samples of Viura and Chardonnay grapes were collected in two locations (Cadreita and Villamayor de Monjardin) which varied in environmental conditions. Mass and sugars content measured by a refractometer and NIR (800-500 nm) refl ectance spectra were obtained. A partial least squares regression (PLS) was made to calibrate the NIR spectra. The regression models for Chardonnay grapes were more robust than for Viura grapes, showing coeffi cients of determination for calibration and validation of 0.75 and 0.70 and a standard error of cross-validation of 1.27. Therefore, NIR technology is suitable to determine the soluble solids content although it requires a calibration model for each variety, using a large number of data points and variables. The combined variety model showed a residual predictive deviation of 1.33, while Viura and Chardonnay models showed 1.54 and 1.88, respectively. The results of discriminant analysis using variables from the NIR spectrum showed a percentage of well-classifi ed grapes according to the variety to which they belonged of 97.2% and a 79.2% of well-classifi ed Chardonnay grapes according to their origin. In conclusion, NIR technology is a useful alternative for identifying the variety and origin of grapes.

Optimisation of the Quantification of Total Soluble Solids, pH and Titratable Acidity in South African Grape Must using Fourier Transform Mid-infrared Spectroscopy

“…In contrast to wine analysis, spectroscopic applications for grape analysis have mostly focussed on the use of visible and near-infrared spectroscopy (Manley et al, 2001;Jarén et al, 2001;Dambergs et al, 2003;Herrera et al, 2003;Arana et al, 2005), and the evaluation of FT-MIR spectroscopy for comprehensive grape analysis has only been reported in a very limited number of publications (Dubernet et al, 2000). Furthermore, the prediction accuracies of the global calibrations, when used for the quantification of grape samples from non-European origin, have not been evaluated thoroughly.…”

“…The selection of calibration samples is therefore very important and, ideally, all the sources of variation to be expected in future unknown samples should be built into the calibration model. Major sources of variation that can affect the accuracy of analytical data generated with infrared spectroscopy if they are not accounted for sufficiently in the calibration model include the chemical composition of samples, the grape cultivar and the geographic origin of the grapes Arana et al, 2005). In the present study, grape samples were selected to be representative of white cultivars (Sauvignon blanc, Chardonnay, Colombar and Chenin blanc) and red cultivars (Merlot, Pinotage, Cabernet Sauvignon and Shiraz) grown in the three major viticultural regions in the Olifants River Region, SA.…”

Prediction of Sugarcane Quality from Juice Samples using Portable Spectroscopy

“…The maximum numbers of LVs used in this study was set to ten. Due to a limited number of samples used, full cross validation (leave-one-out) was used to evaluate the prediction quality and prevent over fitting of the calibration model [11]. External validation method was also used in this study to check the performance of the PLS models.…”

Study on the Authenticity of Identification Methods in White Spirit by Infrared Spectrometer

“…While after the 1980s of the 20th century, with the rapid development of computer technology and chemical methods in the context of spectral information extraction and elimination, the background interference achieved good results, as well as near-infrared spectroscopy in testing technical characteristics that are unique and the understanding of near-infrared spectroscopy for its wide range of applications [2][3][4][5][6][7].…”