Evaluation of Grape Quality Parameters by a Simple Vis/NIR System

Abstract

Visible/near-infrared (Vis/NIR) spectroscopy is a rapid and nondestructive technique requiring minimal sample processing before analysis, and coupled with chemometrics methods it appears to be one of the most convenient and straightforward analytical tools for studying fruit quality and ripeness. Chemometrics is applied to solve both descriptive and predictive problems in the chemical, pharmaceutical, and food sectors. With this aim, an optical, portable, experimental system (Vis/NIR spectrophotometer) for nondestructive and quick prediction of ripening parameters of fresh berries and homogenized samples of grapes in the wavelength range 450-980 nm was built and tested. A total of 156 grape samples, representing vintage years 2005 and 2006 and harvested in the Valtellina viticultural area of Italy, were evaluated by Vis/NIR spectroscopy for ripeness parameters (soluble solids content, titratable acidity, and pH value) and for phenol ripening parameters (anthocyanins and polyphenols content). Accurate and good calibrations to predict ripeness parameters were obtained for both the 2005 and 2006 vintage years. Calibrations for technological ripening and for anthocyanins had good correlation coefficients (r CV >0.90). These models were extensively validated using independent sample sets. Good statistical parameters were obtained for soluble solids content (r > 0.8, SEP < 1.24 °Brix) and for titratable acidity (r > 0.8, SEP < 2.00 g tartaric acid L-1), showing the validity of the Vis/NIR spectrometer. Similarly, anthocyanins could be predicted accurately compared with the reference determination. Finally, for qualitative analysis, spectral data on grapes were divided into two groups on the basis of grapes' soluble content and acidity in order to apply a classification analysis (PLS-DA). Good results were obtained with the Vis/NIR device, with 89% of samples correctly classified for soluble content and 83% of samples correctly classified for acidity. Results indicate that the Vis/NIR portable device could be an interesting and rapid tool for assessing grape ripeness directly in the field or upon receiving grapes in the wine industry.

Testing of a simplified LED based vis/NIR system for rapid ripeness evaluation of white grape (Vitis vinifera L.) for Franciacorta wine

“…Larrain et al [28] also obtained R 2 ¼ 0.87 in validation for SSC using a portable NIR device (640-1300 nm) on Chardonnay grapes under field conditions. Regarding TA, Guidetti et al [29], using a portable vis/NIR system (450-980 nm), showed for fresh berries of red Nebbiolo grapes R 2 cv ¼0.66 and RMSECV¼ 1.48 g dm À 3 . Spectral indexes measured at the four wavelengths on the same samples was used to predict the ripening parameters using MLR analysis ( Table 2).…”

Nondestructive Determination of Soluble Solids Content of ‘Fuji’ Apples Produced in Different Areas and Bagged with Different Materials During Ripening

“…In PLS regression, an orthogonal on the basis of latent variables (LVs) is constructed one by one in such a way that they are oriented to along directions of maximal covariance between the spectral matrix and the variable matrix (Guidetti et al 2010). The LVs were determined using leave-one-sample-out crossvalidation (LOOCV) method combined with the smallest root-mean-square error of cross-validation (RMSECV).…”

Trends in Recent Studies on Post-Harvest Technology

“…They observed that RF treatments, combined with forced hot air at 48°C for 10 min, followed by forced room air cooling through a 3 cm product layer, provided good bean quality. Guidetti et al (2010) investigated a portable optical experimental system (Vis/NIR spectrophotometer) for nondestructive and quick prediction of ripening parameters of fresh berries and homogenized grape samples (Vitis spp.) in the wavelength range of 450-980 nm.…”