The present study was aimed at the identification, differentiation and characterization of red and white Cretan wines, which are described with Protected Geographical Indication (PGI), using ultraviolet–visible absorption spectroscopy. Specifically, the grape variety, the wine aging process and the role of barrel/container type were investigated. The combination of spectroscopic results with machine learning-based modelling demonstrated the use of absorption spectroscopy as a facile and low-cost technique in wine analysis. In this study, a clear discrimination among grape varieties was revealed. Moreover, a grouping of samples according to aging period and container type of maturation was accomplished, for the first time.

In addition, we present results from the correlation of optical spectroscopy data with conventional analytical techniques.

Typical UV-Vis spectra of four different wine samples

Discrimination of Grape Varieties

Discrimination of Wines According to Aging Time

Discrimination of Container Type

Correlation of Absorption Spectroscopy with Classical Analytical Methods

Typical UV-Vis spectra of four different wine samples

Typical Ultraviolet–Visible (UV-Vis) absorption spectra for (a) white wines (Dafni and Vilana) and (b) red wines (Kotsifali and Mandilari).

Discrimination of Grape Varieties





White wine Dafni and Vilana varieties discrimination. (a) Score plot of the first and the third latent variables resulting from the OPLS-DA application on ultraviolet spectral data of 80 white wine samples from three vintages, and (b) The corresponding loading plot. Latent variable 1 is designated by the blue line and latent variable 3 by the red line.

 

 

 

 

Red wine Kotsifali and Mandilari varieties discrimination. (a) Score plot of the first two latent variables resulting from the Orthogonal Partial Least Squares—Discriminant Analysis (OPLS-DA) application on ultraviolet spectral data of 101 red wine samples from three vintages, and (b) The corresponding loading plot. Latent variable 1 is designated by the blue line and latent variable 2 by the red line.

Discrimination of Wines According to Aging Time

 

 

 

Red wine aging time (3, 6, 9 and 12 months) discrimination. (a) Score plot of the first and the second latent variables resulting from the OPLS-DA application on visible spectral data of 48 red wine Kotsifali and Mandilari samples. The assignment of each category of wine samples is shown in the inset, and (b) Corresponding loading plot. Latent variable 1 is designated by the blue line and latent variable 2 by the red line.

Discrimination of Container Type

 

 

 

Maturation container discrimination. (a) Score plot of the first and the second latent variables resulting from the OPLS-DA application on ultraviolet spectral data of the white wine Vilana samples. The assignment of each category of wine samples is shown in the inset, and (b) Corresponding loading plot. Latent variable 1 is designated by the blue line and latent variable 2 by the red line.

Correlation of Absorption Spectroscopy with Classical Analytical Methods

Correlation of Ultraviolet Absorption Spectroscopy with the Concentration of Phenolic Ingredients

Correlation of Ultraviolet Absorption Spectroscopy with Tannins Concentration

Correlation of Visible Absorption Spectroscopy with Anthocyanins Concentration

Correlation of Ultraviolet Absorption Spectroscopy with the Concentration of Phenolic Ingredients

The results of a study on the ability of ultraviolet absorption spectroscopy 220-400nm in predicting the phenolic composition of wine are presented. The Folin-Ciocalteu method was used as a reference method, providing data on the overall phenolic composition of wine. The application of the Folin-Ciocalteu method was carried out by the scientific team of the Laboratory for the Production of Agricultural Products and Propagating Material-Department of Agriculture of the Hellenic Mediterranean University (ELMEPA). The absorption of wine in the ultraviolet region of the electromagnetic spectrum is directly related to phenolic components. Therefore, a strong correlation of the spectral characteristics of wine in ultraviolet with its phenolic composition is expected.

 

 

Comparison of the predicted value obtained from ultraviolet spectroscopy with the corresponding value by the Folin Ciocalteu method

Correlation of Ultraviolet Absorption Spectroscopy with Tannins Concentration

The results of a study on the ability of ultraviolet absorption spectroscopy 220-400nm in predicting the composition of wine in tannins are presented. The Ribereau-Gayon & Stonestreet method was used as a reference method. The application of the method was carried out by the scientific team of the Laboratory for the Production of Agricultural Products and Propagating Material-Department of Agriculture of the Hellenic Mediterranean University (ELMEPA). The absorption of wine in the ultraviolet region of the electromagnetic spectrum is directly related to tannins. Therefore, a strong correlation of the spectral characteristics of wine in ultraviolet with the concentration of tannins is expected.

 

 

 

Comparison of the predicted value obtained from ultraviolet spectroscopy with the corresponding value from the Ribereau-Gayon & Stonestreet method

Correlation of Visible Absorption Spectroscopy with Anthocyanins Concentration

 

 

Comparison of the predicted value obtained from ultraviolet spectroscopy with the corresponding value from the Somers method

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