Multivariate Statistical Analysis of the UV-Vis Profiles of Wine Polyphenolic Extracts during Vinification

Abstract

Multivariate Statistical data Analysis (MVA) was used to study the changes undergone by the UV-Vis spectral profiles of polyphenolic components during vinification. Two Sardinian wines, from the white cultivar "Vermentino" and from the red "Cannonau", were studied. The wine samples were collected at different times from the fermentation vessels and the UV-Vis spectra of their solid phase extracts (SPE) were submitted to PCA (Principal Component Analysis) and to Orthogonal Projections to Latent Structures (OPLS) regression analysis in order to look for the main source of variability present in the spectra in terms of grape typology and winemaking times. In Vermentino, during the first weeks of vinification the prevalent modifications regarded the increase of the bands at 280 and 350 nm, attributed to HBA, stilbenes flavan-3-ols and glycosylated flavonols, respectively; at approximately 60 days a bathocromic shift of the band at 350 nm towards 380 nm took place, suggesting hydrolysis of flavonols. In Cannonau, the band at 536 nm, attributed to anthocyanins, that showed a consistent increase in the first days of vinification, after 11 days dropped significantly, exhibiting also a bathochromic shift. The band at 380 nm was linearly positively correlated with time. Our results support the potential use of this approach for qualitatively monitoring the winemaking process.

Helium Atmospheric Pressure Plasma Jet Source Treatment of White Grapes Juice for Winemaking

“…Spectroscopic methods, like Ultraviolet-to-Visible spectroscopy (UV-Vis) [61][62][63][64], Fourier Transformed Infrared spectroscopy (FTIR) [48,[65][66][67][68][69][70][71] are also applied due to their easiness of use, cost-effective and no sample preparation also in combination with numerical/statistical methods (e.g., chemometric methods) [48,66,68,[72][73][74][75].…”

Mathematical modelling to enhance winemaking efficiency: a review of red wine colour and polyphenol extraction and evolution

“…Conjugation lowers the energy required for electron transitions to take place between OH-phenolic groups, causing an increase of absorption wavelengths in the UV-Vis spectra and subsequent displays of colour (Vallverdú-Queralt et al 2016, Waterhouse et al 2016b. As such, the visible colour of a compound is influenced by its degree of conjugation, with less conjugation causing a material to absorb light at shorter wavelengths (perceived as yellow and red hues) and greater conjugation causing absorption at longer wavelengths (perceived as blue and green hues) (Sanna et al 2014). Experiments have shown that tannins display yellow hues (Amendola et al 2010, Burtch et al 2017, pyranoanthocyanins express red-orange and red-brown hues (Figure 7), copigmentation reactions generate red and brown colours (Amendola et al 2010, Escribano-Bailón et al 2019, Morata et al 2019 and ethyl-linked pigments generate purple colours (Lee et al 2004b).…”

The Role of UV-Visible Spectroscopy for Phenolic Compounds Quantification in Winemaking

“…red anthocyanins or yellow flavonols). The UV-visible spectra of a wine is thus attributed to the electronic transitions occurring within the hydroxyl groups of the phenolic molecules, with different transitions corresponding to the different phenolic subclasses [12]. A number of UV-visible applications have been exploited to quantify phenolic compounds.…”