Inmaculada Romero-Cascales

Improving Grape Phenolic Content and Wine Chromatic Characteristics through the Use of Two Different Elicitors: Methyl Jasmonate versus Benzothiadiazole

Benzothiadiazole (BTH) and methyl jasmonate (MeJ) have been described as exogenous elicitors of some plant defense compounds, polyphenols among them. The objective of this study was to determine whether the application of BTH or MeJ to grape clusters at the beginning of the ripening process had any effect on the accumulation of the main flavonoid compounds in grapes (anthocyanins, flavonols, and flavanols) and the technological significance of these treatments in the resulting wines. The results obtained after a 2 year experiment indicated that both treatments increased the anthocyanin, flavonol, and proanthocyanidin content of grapes. The wines obtained from the treated grapes showed higher color intensity and total phenolic content than the wines made from control grapes. The exogenous application of these elicitors, as a complement to fungicide treatments, could be an interesting strategy for vine protection, increasing, at the same time, the phenolic content of the grapes and the resulting wines.

Increasing Bioactive Phenolic Compounds in Grapes: Response of Six Monastrell Grape Clones to Benzothiadiazole and Methyl Jasmonate Treatments

The application of different elicitors to plants has proved a useful technique for the improvement of their phenolic content. However, studies have shown that the exact response of plants to elicitors depends both on variety and clone. In the present study, two elicitors (benzothiadiazole and methyl jasmonate) were applied in a vineyard where a collection of the six selected clones of Monastrell grape variety were planted to determine whether any observed effect was clone-dependent. The analysis of anthocyanins, flavonols, stilbenes, and seed and skin tannins showed that, in general, both elicitors increased the levels of phenolic compounds in the treated plants, although the extent of the response differed among different clones from the same variety. The positive effect of both benzothiadiazole and methyl jasmonate indicated that such treatments could be regarded as useful for improving grape and wine color while also increasing resistance to some pathogens. However, a preliminary exploratory field study should be carried out since differences in the response of the grapes to treatment might occur, depending on the clone.

Increasing the phenolic compound content of grapes by preharvest application of abcisic acid and a combination of methyl jasmonate and benzothiadiazole.

Benzothiadiazole (BTH) and methyl jasmonate (MeJ) have been described as exogenous elicitors of some plant defense compounds, polyphenols among them. Given that they activate different arrays of biochemical reactions to induce resistance, the objective of this study was to determine whether the joint application of BTH and MeJ to grape clusters affects the level of the main flavonoid compounds in grapes and in the resulting wines. The results are compared with those obtained when abscisic acid (ABA), a plant growth regulator involved in several physiological processes, was sprayed in the same vineyard. The results obtained indicated that, although the application of ABA increased the content of skin anthocyanins and tannins, these positive effects were not reflected in the wines made from these grapes. BTH+MeJ-treated grapes also presented higher anthocyanin and flavonol contents, and in this case, their wines presented better chromatic characteristics that the wine made from control grapes.

The composition of cell walls from grape marcs is affected by grape origin and enological technique

The grape marc obtained after vinification could be a source of high value compounds and the different winemaking techniques could influence such compounds. The composition of skin cell walls from Monastrell grapes grown in three different locations near Murcia (S.E. Spain) has been studied. The grapes were winemaked with three different techniques (cold pre-fermentative maceration, β-galactosidase enzyme addition and enzymatic preparation addition) and the marc skin cell walls were studied to determine their composition. The results suggest that terroir influenced the percentage of grape skin, the amount of cell wall material isolated from the grape skin, the carbohydrate composition of the cell wall material, and the lignin and protein content of the cell wall material from grape skin. A similar trend has been found within the influence of terroir on cell wall material isolated from the skin separated from the marc, being the differences also due to the enological technique.

Cell wall compounds of red grapes skins and their grape marcs from three different winemaking techniques.

Different winemaking practices are aimed at increasing cell wall degradation to facilitate extraction of valuables molecules into the wine. However, little attention has been paid to the composition of marcs from different cultivars according to the influence of the winemaking procedures. We provide information on skin cell walls from Cabernet Sauvignon, Syrah and Monastrell grapes and examine how different winemaking practices (addition of enzymatic preparation and β-galactosidase separately and dry ice addition) may affect the composition of marc skin cell wall material (CWM). The efficiency of CWM isolation from the grape skin and also its composition is influenced by the cultivar. A similar cultivar influence has been detected on CWM from the marc, being the differences also due to the enological technique. Our results help to increase our knowledge on the degradation of cell walls during vinification, while providing a valuable guideline to upgrade the value of these by-products.

Oligosaccharides of Cabernet Sauvignon, Syrah and Monastrell red wines

Wine oligosaccharides were recently characterized and their concentrations, their composition and their roles on different wines remain to be determined. The concentration and composition of oligosaccharides in Cabernet Sauvignon, Syrah and Monastrell wines was studied. Oligosaccharide fractions were isolated by high resolution size-exclusion chromatography. The neutral and acidic sugar composition was determined by gas chromatography. The MS spectra of the oligosaccharides were performed on an AccuTOF mass spectrometer. Molar-mass distributions were determined by coupling size exclusion chromatography with a multi-angle light scattering device (MALLS) and a differential refractive index detector. Results showed significant differences in the oligosaccharidic fraction from Cabernet Sauvignon, Syrah and Monastrell wines. This study shows the influence that the grape variety seems have on the quantity, composition and structure of oligosaccharides in the finished wine. To our knowledge, this is the first report to research the oligosaccharides composition of Cabernet Sauvignon, Syrah and Monastrell wines.