Rootstock effects on grape anthocyanins, skin and seed proanthocyanidins and wine color and phenolic compounds from Vitis vinifera L. Merlot grapevines.

BACKGROUND: Rootstocks affect vegetative and reproductive parameters of the scion. However, limited knowledge exists on the effects of the adoption of a specific rootstock on grape and wine phenolic composition, which contribute to certain sensory attributes such as color, body and astringency of wine. These compounds are mainly affected by the variety, viticultural management and rootstock. The aim of this work was to study the influence of eight rootstocks on grape anthocyanin content, skin and seed proanthocyanidins and wine chromatic characteristics obtained from Merlot vines. RESULTS: Grapevines grafted onto SO4 rootstock, in general, presented a higher concentration of total proanthocyanidins in skins and seeds compared to the rest of the rootstocks, whereas grapevines grafted onto Gravesac presented a lower concentration of proanthocyanidins in skins and seeds. These differences were found in the wines developed from grapevines grafted onto SO4. Wines from grapevines grafted onto SO4, 140 Ruggeri, Gravesac and 4453 M rootstocks presented, in general, better chromatic characteristics and a higher anthocyanin and tannin content than the rest of the samples. CONCLUSION: This work gives additional information concerning the influence of rootstock on grape and wine phenolic composition. © 2018 Society of Chemical Industry.

Characterization of phenolic composition in Carignan noir grapes (Vitis vinifera L.) from six wine-growing sites in Maule Valley, Chile.

BACKGROUND: Among Chilean varieties, Carignan noir has had a major resurgence due to its rediscovered wine quality potential. For this, the aim of this study was to characterize phenolic composition of grapes grown in six sites from the Maule Valley. RESULTS: The data showed that myricetin-3-glc and catechin were the most important flavonol and flavanol, respectively. Anthocyanin and flavonol composition was correlated with biologically effective degree days, exhibiting a relationship with grape maturity. Flavanol and hydroxycinnamic acid composition was inversely correlated to the average maximum temperature of the warmest month, showing that their synthesis is favored by cooler temperatures during the warmest month. CONCLUSION: These results have enological and viticultural interest for grape growers as vineyard site selection for this cultivar can confer differentiable attributes in terms of grape composition and quality. On the other hand, understanding the effects of climate on the synthesis of phenolic compounds may be useful for managing the vineyards with the aim of improving grape quality. © 2017 Society of Chemical Industry.

Effect of eugenol and guaiacol application on tomato aroma composition determined by headspace stir bar sorptive extraction.

BACKGROUND: The present work was carried out because there is only a small amount of literature on how the volatile composition of tomatoes can be modified by the effect of exogenous substances in contact with tomato plants. This work studies how eugenol and guaiacol, either by foliar application and/or in the surrounding atmosphere, can affect the volatile composition of this fruit. An important work of this study was also conduced to validate the analytical method [headspace stir bar sorptive extraction-gas chromatography-mass spectrometry (HS-SBSE-GC-MS)] to determine the composition of the volatiles in tomato. RESULTS: Analytical method validation parameters such as linearity, limit of detection, limit of quantification, and recovery proved that this method is suitable for the analysis of tomato volatiles. Their eugenol and guaiacol content changed, with an increase of 200 and 35 times, respectively, when foliar treatment was used, and an increase of 10, in both cases, when plants were in contact with the contaminated atmosphere. As consequence of the treatments other volatile compounds changed considerably. CONCLUSION: For first time, a HS-SBSE-GC-MS method was successfully validated for the study of volatiles in tomatos. Results suggests that exogenous compounds in contact with the plants, such as eugenol and guaiacol, can be absorbed changing the global volatile composition of fruits, which could produce a negative or positive effect in their aroma.

Effect of size, seasoning and toasting level of Quercus pyrenaica Willd. wood on wine phenolic composition during maturation process with micro-oxygenation.

Seasoning and toasting treatments carried out in cooperage influence the chemical composition of the oak, and these treatments affect different oak species in different ways. For this reason, numerous studies have focused on the evaluation of both the oak wood materials and the resulting aged wines in order to optimize the different cooperage processes. Seasoning involves immobilizing the wood for long periods of time, leading to an increase in the price of the final product. When using alternative products instead of barrels, in addition to the seasoning and toasting of the wood, the size of the wood pieces is a determining factor in the characteristics of the final wine. Therefore, the objective of this work was to evaluate the polyphenolic composition of the same red wine aged with different alternative products and a small amount of oxygen for 120 days. Specifically, the effect of 2 types of seasoning and 3 types of toasting of chips and staves made from the wood of Q. pyrenaica Willd. was studied. The results showed that the size of the alternative product was the factor that determines the phenolic composition of the wines over the entire ageing process, independent of the seasoning or toasting method carried out on the wood.

Volatile composition and sensory characteristics of Carménère wines macerating with Colombian (Quercus humboldtii) oak chips compared to wines macerated with American (Q. alba) and European (Q. petraea) oak chips.

Different oak species or origins have been studied to find an alternative to traditional ones and Quercus humboldtii from Colombia is a candidate. Some studies analyse the composition of this oak, but no work has been found to study its use for wine treatment. The aim was to evaluate volatile composition of toasted Q. humboldtii oak chips and the wines treated with these chips. To evaluate its oenological potential Q. alba and Q. petraea have been included in this trial. The wines were subjected to a sensory analysis. Results indicated that oak chips and wines macerated for 90 days with toasted Colombian chips exhibited higher 5-methylfurfural, guaiacol, trans-isoeugenol and syringol concentrations than others, while the furfural and cis-ß-methyl-γ-octalactone content was lower. Sensory analysis showed that the wines treated with Colombian oak presented more notes of smoked and less of coconut. Therefore, this oak could probably be considered suitable for ageing.

Foliar nitrogen application in Cabernet Sauvignon vines: Effects on wine flavonoid and amino acid content.

Wine quality greatly depends on its chemical composition. Among the most important wine chemical compounds, flavonoids are the major contributors to wine organoleptic properties while amino acids have a huge impact on fermentation development and wine volatile profile. Likewise, nitrogen applications are known to have an impact on wine composition. Therefore, the aim of this work was to study the effects of foliar nitrogen applications on wine flavonoid and amino acid composition. The experiment involved five foliar nitrogen applications at veraison time: urea (Ur), urea plus sulphur (Ur+S), arginine (Arg), and two commercial fertilizers Nutrimyr Thiols (NT) and Basfoliar Algae (BA). The results showed that nitrogen foliar treatments decreased wine flavonoid content although the effect varied according to each treatment. This could be related to a low vine nitrogen requirement, since must yeast assimilable nitrogen (YAN) was above acceptable threshold values for all samples. With regard to wine amino acid content, all treatments except for Ur increased its values after the applications. Finally, foliar nitrogen treatments greatly influenced wine composition. Among them, urea seemed to exert the most negative effect on both phenolics and amino acids. In addition, an inverse relationship between wine amino acid content and flavonol concentration was exhibited.

Glycosidic aroma precursors of Syrah and Chardonnay grapes after an oak extract application to the grapevines.

Syrah and Chardonnay grapevines were treated with an oak extract in order to determine the effect on glycosidic aroma precursors. Grapevines were treated at three different timings of the veraison (treatment 1, 2 and 3). Aglycons were obtained by enzymatic hydrolysis, and these were identified and quantified by means of gas chromatography-mass spectrometry (GC-MS). Results suggest that after the applications the majority of compounds from the oak extract were assimilated and stored as glycosidic forms in both cultivars. Also, other compounds not present in the extract were affected, with a different behaviour observed depending on the timing of application and the variety. In general, C6 compounds, alcohols, terpenes, phenols and C13-norisoprenoids in Syrah showed a decrease and in Chardonnay an increase. Thus, this study proved a change in the glycosidic aroma profile in grapes after the oak application, so these treated grapes could produce wines with different aromatic quality.

Volatile compounds formation in alcoholic fermentation from grapes collected at 2 maturation stages: influence of nitrogen compounds and grape variety.

The aim of this work was to study the influence of nitrogen compounds on the formation of volatile compounds during the alcoholic fermentation carried out with 4 nonaromatic grape varieties collected at 2 different maturation stages. To do this, Monastrell, Merlot, Syrah, and Petit Verdot grapes were collected 1 wk before harvest and at harvest. Then, the musts were inoculated with the same Saccharomyces cerevisiae yeast strain and were fermented in the same winemaking conditions. Amino acids that showed the highest and the lowest concentration in the must were the same, regardless of the grape variety and maturation stage. Moreover, the consumption of amino acids during the fermentation increased with their concentration in the must. The formation of volatile compounds was not nitrogen composition dependent. However, the concentration of amino acids in the must from grapes collected 1 wk before harvest can be used as a parameter to estimate the concentration of esters in wines from grapes collected at harvest and therefore to have more information to know the grape oenological capacity. Application of principal components analysis (PCA) confirmed the possibility to estimate the concentration of esters in the wines with the concentration of nitrogen compounds in the must.

Effect of oak extract application to Verdejo grapevines on grape and wine aroma.

Volatile compounds from a commercial aqueous oak extract application to white Verdejo grapevines at veraison have been studied. Treated grapes under two types of formulation (25% and 100%) have been analyzed at the optimum maturation time, and winemaking was then subsequently carried out. The volatile compounds were analyzed by stir bar sorptive extraction-gas chromatography-mass spectrometry. The results suggest that after the grapevine treatments, grapes store the volatiles in the form of nonvolatile precursors, and some of the volatiles are released during the winemaking process, especially six months after the alcoholic fermentation. The sensory analysis shows that wines maintain the typical aroma properties of Verdejo wines at the end of fermentation; but after six months, the wine color is greener and more astringent, and, in terms of aroma, it has wooden notes as if the wine has been aged in oak barrels.