Natalia Quijada-Morín

Polyphenolic, polysaccharide and oligosaccharide composition of Tempranillo red wines and their relationship with the perceived astringency

The influence of the proanthocyanidic, polysaccharide and oligosaccharide composition on astringency perception of Tempranillo wines has been evaluated. Statistical analyses revealed the existence of relationships between chemical composition and perceived astringency. Proanthocyanidic subunit distribution had the strongest contribution to the multiple linear regression (MLR) model. Polysaccharide families showed clear opposition to astringency perception according to principal component analysis (PCA) results, being stronger for mannoproteins and rhamnogalacturonan-II (RG-II), but only Polysaccharides Rich in Arabinose and Galactose (PRAGs) were considered in the final fitted MLR model, which explained 96.8% of the variability observed in the data. Oligosaccharides did not show a clear opposition, revealing that structure and size of carbohydrates are important for astringency perception. Mannose and galactose residues in the oligosaccharide fraction are positively related to astringency perception, probably because its presence is consequence of the degradation of polysaccharides.

Relationship between the sensory-determined astringency and the flavanolic composition of red wines.

The relationship between the proanthocyanidin profile and the perceived astringency was assessed in 13 commercial Tempranillo red wines. The concentration and compositional information were obtained by liquid chromatography with diode array detection coupled to electrospray ionization mass spectrometry after acid-catalyzed depolymerization of wine proanthocyanidins in the presence of excess phloroglucinol. Statistical analysis of the results showed significant correlations between sensory and chemical determinations. Astringency was more affected by the subunit composition than by the total concentration or the average degree of polymerization of wine proanthocyanidins. Higher proportions of epicatechin (EC) subunits in extension positions and gallocatechin (GC) subunits in terminal positions were shown to increase astringency. On the contrary, the amount of epigallocatechin (EGC) in both extension and terminal positions was negatively correlated with the perceived astringency.

Relationship between skin cell wall composition and anthocyanin extractability of Vitis vinifera L. cv. Tempranillo at different grape ripeness degree

The relationship between cell wall composition and extractability of anthocyanins from red grape skins was assessed in Tempranillo grape samples harvested at three stages of ripening (pre-harvest, harvest and over-ripening) and three different contents of soluble solids (22, 24 and 26 °Brix) within each stage. Cell wall material was isolated and analysed in order to determine cellulose, lignin, non-cellulosic polysaccharides, protein, total polyphenols index and the degree of esterification of pectins. Results showed the influence of ripeness degree and contents of soluble solids on cell wall composition. Furthermore, principal components analysis was applied to the obtained data set in order to establish relationships between cell wall composition and extractability of anthocyanins. Total insoluble material exhibits the biggest opposition to anthocyanin extraction, while the highest amounts of cellulose, rhamnogalacturonans-II and polyphenols were positively correlated with anthocyanin extraction. Moreover, multiple linear regression was performed to assess the influence of the cell wall composition on the extraction of anthocyanin compounds. A model connecting cell wall composition and anthocyanin extractabilities was built, explaining 96.2% of the observed variability.

Application of Differential Colorimetry To Evaluate Anthocyanin–Flavonol–Flavanol Ternary Copigmentation Interactions in Model Solutions

The combined effect of anthocyanin-flavanol-flavonol ternary interactions on the colorimetric and chemical stability of malvidin-3-glucoside has been studied. Model solutions with fixed malvidin-3-glucoside/(+)-catechin ratio (MC) and variable quercetin-3-β-d-glucoside concentration (MC+Q) and solutions with fixed malvidin-3-glucoside/quercetin-3-β-d-glucoside ratio (MQ) and variable (+)-catechin concentration (MQ+C) were tested at levels closer to those existing in wines. Color variations during storage were evaluated by differential colorimetry. Changes in the anthocyanin concentration were monitored by HPLC-DAD. CIELAB color-difference formulas were demonstrated to be of practical interest to assess the stronger and more stable interaction of quercetin-3-β-d-glucoside with MC binary mixture than (+)-catechin with MQ mixture. The results imply that MC+Q ternary solutions kept their intensity and bluish tonalities for a longer time in comparison to MQ+C solutions. The stability of malvidin-3-glucoside improves when the concentration of quercetin-3-β-d-glucoside increases in MC+Q mixtures, whereas the addition of (+)-catechin in MQ+C mixtures resulted in an opposite effect.

Characterization of Sensory Properties of Flavanols—A Molecular Dynamic Approach

In this work, sensations elicited by catechin and procyanidins in comparison with those elicited by gallocatechin and prodelphinidins were evaluated by means of a sensory panel. To obtain further insights into the mechanisms of action, molecular dynamics (MD) simulations and saturation transfer difference nuclear magnetic resonance (STD NMR) experiments have been performed. Results showed clear differences between the 2 types of flavanols. Dihydroxylated B-ring flavanols were more astringent, bitter, dry, rough, unripe, and persistent than trihydroxylated B-ring ones. Besides, these last compounds were smoother, more velvety, and viscous. MD simulations and STD NMR experiments support results obtained from tasting panel. MD results suggested that catechin binds to a human salivary proline-rich peptide IB714 faster than gallocatechin and this interaction is maintained longer. IB714 can interact with 2 catechin molecules concurrently while only interacts with 1 gallocatechin molecule. Accordingly, STD NMR experiments showed a greater affinity of catechin than gallocatechin for the peptide (K D = 2.7 and 25.7, respectively). Results indicate that the number of hydroxyl substituents present in B-ring of the flavanic nucleus is decisive for the interaction with salivary proteins and the development of astringency perception.

Physico-chemical and chromatic characterization of malvidin 3-glucoside-vinylcatechol and malvidin 3-glucoside-vinylguaiacol wine pigments.

The physicochemical and chromatic features of malvidin 3-glucoside-vinylcatechol (PA1) and malvidin 3-glucoside-vinylguaiacol (PA2) adducts were investigated. Important differences between both pigments were observed. In the investigated pH range (2.0-4.5), our results suggest that PA1 could be considered as a noncovalent dimer of two pyranoflavylium ions (AH)2 which undergo a hydration reaction in two successive steps, with no proton transfer. In contrast, only proton transfer equilibrium between the pyranoflavylium ion and the quinonoid bases was observed for PA2. The hydration and acidity thermodynamic constants of both pyranoanathocyanins were determined by UV-vis spectroscopy. Pigment PA1 was shown to be less sensitive to bisulfite addition than to water addition, and PA2 seems to be largely insensitive to both water and bisulfite additions. The binding constants for the interaction between the pigments and (+)-catechin in aqueous solution and the changes in the CIELAB parameters that it provoked were also determined. The huge increase in the absorption of the pyranoflavylium ion of PA2 when it binds catechin has no equivalent for anthocyanins and nicely outlines the potential of pyranoanthocyanins in the expression of natural colors.

Influence of the physiological stage and the content of soluble solids on the anthocyanin extractability of Vitis vinifera L. cv. Tempranillo grapes

The influence and the extent of the anthocyanin extractability from grape skins at different physiological stages and different soluble solids contents within each stage were investigated. For this purpose three different physiological stages (pre-harvest, harvest and over-ripening) and three soluble solids contents (22, 24 and 26°Brix) within each stage were taken into account using Vitis vinifera L. cv. Tempranillo. This study revealed the influence of physiological stages and soluble solids contents on the amounts of anthocyanins. The most important factor was the physiological stage although the soluble solid contents effect was also relevant, especially for anthocyanins monoglucosides. The highest contents in anthocyanins were found at pre-harvest, following by harvest and finally at over-ripening. Within each physiological stage, the relative abundance of acylated derivatives was influenced by the soluble solids contents. The percentages of acylated anthocyanins tend to decrease as the soluble solids contents. Differences in the anthocyanin extractabilities were highly influenced by the physiological stages and in a lesser extent by the soluble solids contents. The lowest extraction percentages were obtained in pre-harvest samples whatever soluble solids contents. Over-ripening samples present the lowest contents of anthocyanins but these compounds are easily released from tissues to the hydroalcoholic solution providing the highest extraction percentages. Generally, non-acylated anthocyanins were better extracted than the acylated anthocyanins.

Extractability of Low Molecular Mass Flavanols and Flavonols from Red Grape Skins. Relationship to Cell Wall Composition at Different Ripeness Stages.

Flavonol and flavan-3-ol extractabilities from red grape skins were evaluated in Tempranillo grapes harvested at different ripeness stages and with different soluble solid contents within each stage. Flavan-3-ol extractability is related to ripeness stage and also to cell wall composition, mainly to arabinogalactans (AG), mannans, rhamnogalacturonans-I (RG-I), homogalacturonans (HG), xyloglucans (XG), and total polysaccharides content, which are negatively correlated to flavan-3-ol extractability, whereas soluble solid content did not exert any influence on their extraction. Moreover, procyanidin extraction is more strongly related to cell wall composition than prodelphinidin extraction. Flavonol extractability was not influenced by insoluble material contents; although some cell wall components presented a relationship with flavonol extractability, the presence of AG and mannans would decrease total flavonol extractability, whereas protein is positively related to total and major flavonol compounds (i.e., quercetin and myricetin derivatives). The different behaviors observed between those two groups of polyphenol compounds could be due to different tissue and cellular location.

Effect of Salt Stress in the Regulation of Anthocyanins and Color of Hibiscus Flowers by Digital Image Analysis

The effect of salt stress (200 mM NaCl for 28 days) on physiological characteristics of Hibiscus rosa-sinensis, such as abscisic acid (ABA) content, electrolyte leakage, and photochemical efficiency in leaves, and its influence on biomass production, anthocyanin composition, and color expression of flowers were evaluated. Salinity significantly increased electrolyte leakage and ABA content in leaves and reduced the flower fresh weight. Chlorophyll fluorescence parameters were lower in salt stress condition, compared to control. Moreover, salt stress negatively affected the content of anthocyanins (mainly cyanidin-3-sophoroside), which resulted in a visually perceptible loss of color. The detailed anthocyanin composition monitored by HPLC-DAD-MS and the color variations by digital image analysis due to salt stress showed that the effect was more noticeable at the basal portion of petals. A forward stepwise multiple regression was performed for predicting the content of anthocyanins from appearance characteristics obtained by image analysis, reaching R-square values up to 0.90.

Relationship between Agronomic Parameters, Phenolic Composition of Grape Skin, and Texture Properties of Vitis vinifera L. cv. Tempranillo.

The relationship between the agronomic parameters of grapevine and the phenolic composition of skin of Vitis vinifera L. cv. Tempranillo grapes was assessed. The physical and mechanical properties of berries and their skins were also determined and correlated to the chemical composition. Results showed a significant negative correlation between grapevine vigor-related parameters (such as leaf area and bunch weight) and anthocyanin composition, whereas the percentage (w/w) of seeds was negatively correlated with the amount of flavanols of grape skins. Texture properties of grape skins also showed an important relationship with chemical composition. Berry hardness showed a negative correlation with the coumaroyl-anthocyanin derivatives, but it was positively correlated to skin flavanic composition. Moreover, significant regressions with high coefficients of determination were found between phenolic composition and grapevine vigor-related and texture variables, thus pointing out that these parameters might be useful for estimating the phenolic composition of grape skins.