Content Of Grapes Research Articles

Differences in Soil Water Holding Capacity and Available Soil Water along Growing Cycle Can Explain Differences in Vigour, Yield, and Quality of Must and Wine in the DOCa Rioja

Soil water availability during the vine growth cycle can affect yield and grape quality. The objective was to evaluate the effect of soil water holding capacity (AWC) and available soil water (ASW) throughout the growing cycle on the nutritional status, vigor, production, and composition of grapes and wine. The study was conducted in the municipality of Uruñuela in the DOCa Rioja (Spain). The soils of four rainfed vineyard plots were characterized to determine AWC and its impacts on vine, grape, and wine composition. The N, P, and K foliar content, vigor, grape yield, berry weight, and composition of must and wine were analyzed in those vineyard plots during the period 2010–2014. The ASW was simulated in each plot and each year analyzed, considering the soil properties and the weather conditions, after model calibration in one plot in which soil water content was registered. The results showed that AWC influenced ASW along the growing cycle, so vines suffered from water stress in some periods of the vegetative cycle. Plots with higher AWC had higher ASW from fruit set to ripening and lower water stress during this period, which explains the higher N, P, and K foliar content, vigor and grape yield, and lower polyphenol and anthocyanin content in grapes and wines. The period where water availability had the most influence on the quality of the grapes was from veraison to ripening, during which ASW increased berry weight and acidity and decreased anthocyanins and polyphenolic compounds.

Irrigation decreases flower cover and beneficial arthropod abundances in Mediterranean vineyards

Over the last decades, the use of irrigation in vineyards has grown exponentially in response to climate change. In the Mediterranean region, irrigation is the most widely used method of preventing water stress and high sugar content in grapes. However, little is known about potential irrigation effects on biodiversity. This study aims to understand the effect of irrigation on inter-row vegetation, on the abundance of beneficial arthropods and on the predation of pest insects. In the Luberon region of South-Eastern France, nine irrigated and nine non-irrigated vineyards were analysed. Drip irrigation was applied only during the two driest months of the growing season. We found lower flower cover in irrigated vineyards but no difference in species richness and total vegetation cover. Similarly, abundances of several beneficial arthropods were directly affected by irrigation, such as crab spiders, ladybirds, ladybird larvae and parasitic wasps. Structural equation modelling (SEM) revealed that negative irrigation effects on these arthropods were mediated by negative effects on flower cover. Predation rates were also lower in irrigated vineyards but only during daytime. Grapevine yield was not affected by irrigation. Experiments manipulating water availability under controlled conditions may help to understand this surprisingly strong effect of irrigation on flower cover and beneficial arthropod abundance.

Foliar application of methyl jasmonate and methyl jasmonate + urea: effect on nitrogen compounds in Tempranillo grapes over two vintages

The effects of foliar application of methyl jasmonate and methyl jasmonate plus urea on the amino acids content of Tempranillo grapes were evaluated during two seasons (2019 and 2020). In 2019, the foliar treatments favored an increase in ammonium nitrogen (N), amino N and yeast assimilable N when compared to the control grapes; whereas, in 2020, treatments did not affect N parameters in grapes. In 2019, foliar application of both treatments was effective in improving amino acids content in grapes, being significantly higher the effect of methyl jasmonate plus urea treatment than methyl jasmonate treatment. However, in 2020, the effect of both treatments on amino acid content was minor. The different effect among seasons could be explained by environmental conditions and by the differences in N content in grapevines. A multifactorial analysis and discriminant study were carried out, showing that both treatments enhanced amino acid content in grapes. The effect of methyl jasmonate plus urea was stronger than the effect of methyl jasmonate treatment. Also, a great effect of season on amino acids composition was observed.

Variety and year: Two key factors on amino acids and biogenic amines content in grapes

Amino acids have proved to play a key role in the development of volatile compounds present in wine with determining repercussions on the final wine bouquets. Biogenic amines originate from the chemical transformations of amino acids found in various foods, a phenomenon that has given rise to several health-related concerns among consumers. In the present research, the evaluation of two of the most influential factors: variety (genetic) and year (climatic conditions) on these compounds in grapes has been performed. Eight Vitis vinifera varieties have been collected during three years and the content of nineteen amino acids, two biogenic amines, and the ammonium ion has been quantified using the HPLC-PDA technique. The genetic factor has proved to be an influential variable (p-value < 0.05) with mean values of amino acids ranging from 896.89 to 1713.79 mg/L and of biogenic amines ranging from 10.61 to 22.28 mg/L. The climatic conditions have shown to be an influential factor as well (p-value < 0.05), being the low temperatures and rainfall and the high solar radiation favour the development of the amino acid and avoid biogenic amines accumulation in grapes.

Total Soluble Solids in Grape Must Estimation Using VIS-NIR-SWIR Reflectance Measured in Fresh Berries

Total soluble solids (TSS) is a key variable taken into account in determining optimal grape maturity for harvest. In this work, partial least square (PLS) regression models were developed to estimate TSS content for Godello, Verdejo (white), Mencía, and Tempranillo (red) grape varieties based on diffuse spectroscopy measurements. To identify the most suitable spectral range for TSS prediction, the regression models were calibrated for four datasets that included the following spectral ranges: 400–700 nm (visible), 701–1000 nm (near infrared), 1001–2500 nm (short wave infrared) and 400–2500 nm (the entire spectral range). We also tested the standard normal variate transformation technique. Leave-one-out cross-validation was implemented to evaluate the regression models, using the root mean square error (RMSE), coefficient of determination (R2), ratio of performance to deviation (RPD), and the number of factors (F) as evaluation metrics. The regression models for the red varieties were generally more accurate than the models of those for the white varieties. The best regression model was obtained for Mencía (red): R2 = 0.72, RMSE = 0.55 °Brix, RPD = 1.87, and factors n = 7. For white grapes, the best result was achieved for Godello: R2 = 0.75, RMSE = 0.98 °Brix, RPD = 1.97, and factors n = 7. The methodology used and the results obtained show that it is possible to estimate TSS content in grapes using diffuse spectroscopy and regression models that use reflectance values as predictor variables. Spectroscopy is a non-invasive and efficient technique for determining optimal grape maturity for harvest.

Multimodal close range hyperspectral imaging combined with multiblock sequential predictive modelling for fresh produce analysis

Multimodal measurements are increasingly becoming common in the domain of spectral sensing and imaging for fresh produce. Often multiple sensors are expected to carry complementary information which allows precise estimation of responses. In this study, a novel case of multimodal hyperspectral imaging is described where two different spectral cameras working in the complementary spectral ranges were integrated into a fully standalone system for spectral imaging for fresh produce analysis. Furthermore, a comparative analysis of different multiblock predictive modelling approaches for fusing data from these two complementary spectral cameras is demonstrated. Both multiblock latent space and multiblock variable selection approaches to identify key variables of interest was examined and compared with the analysis carried out on individual data blocks. Prediction of the soluble solids content in grapes was used to demonstrate the application. The presented approach can increase the applications of multimodal hyperspectral imaging for non-destructive analysis.

Assessment of the qualitative and quantitative characteristics of the grapes of grapevine cultivar Fokiano (Vitis vinifera L.) in Ikaria Island, under vineyard conditions

This study aimed at assessing the phenolic potential of indigenous Greek red grapevine cultivar Fokiano under different cultivation systems and altitudes, during the cultivation season 2019-2020, which could explore different approaches yielding better results in the same viticultural area, as is Ikaria Island. The samples of the present study were collected from productive (commercial) vineyards in the island of Ikaria, in the region of the North Aegean Sea. Samples of grapes were collected from 7 different vineyards at the northern part of Ikaria with different characteristics: (i) difference in the altitude of the vineyards and (ii) difference in the cultivation system (conventional or organic). The vineyards in question are located at an altitude of 200 m, 400 m, 600 m and 800 m. The samples were collected during the dates of harvest, which were determined according to the technological maturation of the grapes in combination with the biodynamic calendar. In all samples, the mechanical analyses of the grapes and berries took place and the characters of the must as well as the qualitative characters of the berries (must, skins, seeds) were studied. Total soluble solids of the must were calculated using a refractometer, the active acidity (pH) using a pH meter and the total acidity using a sodium hydroxide solution (NaOH). The mechanical analyses that were performed involved the weight of thirty (30) berries, the weight of the grape and the length and width of the berries and the grapes of each sample. The content of grape's skin in total anthocyanins, total phenolics, condensed tannins, total ortho-diphenols, total flavonoids, total flavanols, total flavonols and flavones and their antioxidant capacity with the use of FRAP and DPPH methods were determined using a spectrophotometer. The most important acids found in grapes were identified using High-Performance Liquid Chromatography (HPLC). The measurements in the grape seeds were made on the same compounds as the skins, except for total anthocyanins. The results of the present study showed that the altitude does not seem to have a significant effect on most of the qualitative and quantitative characters of the cultivar in Ikaria, however, in future studies, other factors that affect the qualitative characters of the grapes need to be taken into consideration and further evaluated. The microclimate of the highest altitude (800 m) had a positive effect regarding total phenolics, anthocyanins, tannins, flavonols, o-diphenol content and the antioxidant capacity of the skins according to FRAP method, but with opposite results in the case of the seeds. At the same time, it should be noted that no accurate conclusion can be drawn regarding the cultivation system (conventional or organic), since between the two pairs of conventional and organic vineyards (samples from conventional and organic vineyards at an altitude of 200 m - samples from conventional and organic vineyard at an altitude of 600 m), the measurements exhibit a variation in their results. The antioxidant capacity that was determined in the samples of Fokiano is also remarkable, when also compared with other indigenous red grapevine cultivars. In view of climate change, the exploitation of indigenous varieties under different soil and climatic conditions or even in the same viticultural region, like the one of the current experiment (different cultivation system, different altitude in the island of Ikaria) could unlock and highlight the full potential of such local varieties, depending on the final style of the wine produced.

Evolution of Physicochemical Properties and Phenolic Maturity of Vilana, Vidiano, Kotsifali and Mandilari Wine Grape Cultivars (Vitis vinifera L.) during Ripening.

Determining the optimum harvest time is a significant factor affecting the quality of the grapes and the wine. Monitoring the evolution of grapes' physicochemical properties and phenolic maturity during ripening could be a valuable tool for determining the optimum harvest time. In this study, the total phenolic content, antioxidant activity, flavonols, flavanols, anthocyanins and resveratrol content were determined during the last weeks of ripening for the white cultivars Vilana and Vidiano, as well as for the red cultivars Kotsifali and Mandilari (Vitis vinifera L.). According to the results, an early harvest for the white cultivars and a late harvest for the red cultivars may increase the total phenolics and trans-resveratrol content in grapes and wine. An early harvest would be desirable to maintain high flavanols content and high levels of antioxidant activity in the grapes' skin and seeds. Conversely, a late harvest for the red cultivars may be desirable to increase the total flavonols and anthocyanin content in grapes and wines.

Ethanol-lactate transition of Lachancea thermotolerans is linked to nitrogen metabolism

Climate change increases sugar content in grapes, resulting in unwanted increase in ethanol content of wine. Lachancea thermotolerans ferments glucose and fructose into both ethanol and lactate, decreasing final ethanol content and positively affecting wine acidity. Reported Lachancea thermotolerans strains show big variation in lactate production during fermentation. However, a mechanistic understanding of this lactate producing phenotype is currently lacking. Through a combination of metabolomics, transcriptomics, genomics and computational methods we show that the lactate production is induced by amino acid limitation in a high lactate producing strain. We found in fermentations in synthetic grape juice media that lactate production starts in the last stages of growth, marked by decreased growth rate and increased expression levels of stress related genes. This onset of lactate production is specific for the high lactate producing strain and independent of oxygen availability. The onset of lactate production was changed by increased amino acid content of the media, and it is shown by both computational methods and amino acid measurements that at the onset of lactate production amino acids become limiting for growth. This study shows that lactate production of Lachancea thermotolerans is directly linked to nitrogen availability in the media, an insight that can further aid in the improvement of wine quality.

Impact of Grape Maturity on Ester Composition and Sensory Properties of Merlot and Tempranillo Wines

The goal of this study was to evaluate how grape composition modifications linked to maturity level could affect the wine ester composition and aromatic expression. An experimental design has been developed from grapes of Vitis vinifera cv Merlot and cv Tempranillo. On each vine plot, grapes have been harvested at two maturity levels and have been fermented using a commercial yeast strain under standardized conditions, specifically after having the sugar and nitrogen concentrations adjusted to the same target values. Tempranillo wine ester content was not impacted by the maturity level, whereas Merlot wines from the highest maturity level showed lower concentrations for fatty acid ethyl esters and higher alcohol acetates but higher concentrations for substituted ethyl esters. Sensory analysis corroborated these analytical results: when Merlot maturity increased, wine fruity aromatic expression decreased (particularly its global intensity and the fresh, red-berry, and fermentative fruit characters). In addition, aromatic reconstitution experiments showed that esters were not, alone, responsible for the sensory differences linked to grapes' maturity. Globally, our results highlight the role of esters in the overall wine fruity aromatic expression associated to Merlot ripeness and show that their levels are impacted by other parameters than the grape content in sugars and amino acids, well known as being their precursors.

Pre-Harvest Application of Multi-Walled Carbon Nanotubes Improves the Antioxidant Capacity of ‘Flame Seedless’ Grapes during Storage

As a widely distributed fruit, grapes are susceptible to oxidative damage during storage and transportation, resulting in declining quality and commodity value. This study aimed to investigate the effects of preharvest application of different concentrations of multi-walled carbon nanotubes (MWCNTs) on the postharvest quality of ‘Flame Seedless’ grapes. The results showed that low-concentration (25 and 50 mg L−1) MWCNTs treatments maintained the comprehensive quality index, firmness, soluble sugar, titratable acid, pH value, and ascorbic acid (AsA) content of grapes. MWCNTs at 25 and 50 mg L−1 increased the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and ascorbic acid (APX). Furthermore, MWCNTs reduced the malondialdehyde (MDA) content and decreased the accumulation of excessive reactive oxygen species (ROS) in grape peel and pulp tissues. In addition, transmission electron microscopy (TEM) images demonstrated that MWCNTs were absorbed by parenchymal cells in the grape peel and pulp through the epidermal cell layer. MWCNTs with a specific concentration can be used as a new inducer for the biosynthesis of antioxidants to reduce oxidative damage in grapes during storage.

Influence of elicitors application to Monastrell and Tempranillo vineyards on grape nitrogen composition over two vintages

Currently, elicitors have been used to induce the defence mechanisms of vines, i.e., against both abiotic and biotic stresses. Besides, increases in phenolic synthesis in grapevines have been reported after elicitors application. However, its effects on the grape nitrogen composition are not entirely known. Thus, this work aimed to study the effect of methyl jasmonate (MeJ) and a yeast extract (YE) applied in Monastrell and Tempranillo grapevines on grape amino acids during two consecutive seasons. Amino acids in grapes were analysed by HPLC. In the first season, the total amino acid content in grapes decreased in Monastrell after MeJ and YE applications from 2236 to 1580 and 1620 mg L-1, respectively, while in Tempranillo, the total amino acid concentration decreased after YE applications from 2355 to 1811 mg L-1. However, during the second season, elicitors did not affect total amino acid concentration. The most important components of variability in amino acid concentration were the grape variety and the season. These results provide new knowledge of the effect of two elicitors in two important red varieties on grape amino acids content, relevant for wine quality.

Effects of grape phylloxera leaf infestation on grapevine growth and yield parameters in commercial vineyards: a pilot study

Grape phylloxera (Daktulosphaira vitifoliae) can infest both roots and leaves of Vitis species. In commercial vineyards planted with Vitis vinifera scions grafted on rootstocks, grape phylloxera infestation is generally limited to root feeding. Vineyards are, however, increasingly subjected to vineyard-wide foliar infestations that last throughout the growing season. While some vineyards are affected by the infestation pressure of external leaf-feeding populations, other annually affected V. vinifera vineyards do not have these in their vicinity. Much is known about the damage potential of grape phylloxera root feeding; however, data on how phylloxera leaf infestation affects V. vinifera grapevines in commercial vineyards are lacking. This study, therefore, aimed to assess whether grapevine growth and yield are affected due to leaf infestation as it occurred in three commercial vineyards in the study area. Treatments were based on phylloxera leaf infestation and additional defoliation. Single-leaf carbon acquisition was measured with gas exchange analyses on healthy and galled leaves. Pruning weight and internode length were measured to assess the effect of leaf infestation and the effect of plant growth and vigour on leaf gall outbreaks. Yield quantity and quality were measured, and grapes were vinified for sensory analyses. Furthermore, using enzymatic analyses, non-structural carbohydrates were analysed in perennial wood. A significant decrease in sugar content in grapes (10 %) and starch reserves in perennial wood (11 %) was found in the most heavily infested vineyard. Grape must of infested plants in another vineyard furthermore showed a significantly higher level of titratable acid (7.5 %). Significant infestation effects seen in one vineyard were not significant in the other two vineyards. No significant differences were seen for carbon acquisition, harvest quantity, wine sensory analysis, pruning weight or internode length. The overall effect of phylloxera leaf infestation in the studied vineyards was, therefore, marginal. Grapevine vigour did not differ between infested vines, insecticide-sprayed vines, and vines on which no leaf infestation outbreaks took place. By analysing phylloxera leaf infestation under field conditions, these preliminary results form a basis for future long-term field studies about phylloxera leaf feeding on Vitis vinifera within the context of other biotic and abiotic plant stresses.

Effect of Methyl Jasmonate Doped Nanoparticles on Nitrogen Composition of Monastrell Grapes and Wines.

Nitrogen composition on grapevines has a direct effect on the quality of wines since it contributes to develop certain volatile compounds and assists in the correct kinetics of alcoholic fermentation. Several strategies can be used to ensure nitrogen content in grapes and one of them could be the use of elicitors such as methyl jasmonate. The use of this elicitor has been proven to be efficient in the production of secondary metabolites which increases the quality of wines, but its use also has some drawbacks such as its low water solubility, high volatility, and its expensive cost. This study observes the impact on the amino acid and ammonium composition of must and wine of Monastrell grapes that have been treated with methyl jasmonate (MeJ) and methyl jasmonate n-doped calcium phosphate nanoparticles (MeJ-ACP). The first objective of this study was to compare the effect of these treatments to determine if the nitrogenous composition of the berries and wines increased. The second aim was to determine if the nanoparticle treatments showed similar effects to conventional treatments so that the ones which are more efficient and sustainable from an agricultural point of view can be selected. The results showed how both treatments increased amino acid composition in grapes and wines during two consecutive seasons and as well as the use of MeJ-ACP showed better results compared to MeJ despite using less quantity (1 mM compared to 10 mM typically). So, this application form of MeJ could be used as an alternative in order to carry out a more efficient and sustainable agriculture.

Biotechnological Approaches to Lowering the Ethanol Yield during Wine Fermentation.

One of the most prominent consequences of global climate warming for the wine industry is a clear increase of the sugar content in grapes, and thus the alcohol level in wines. Among the several approaches to address this important issue, this review focuses on biotechnological solutions, mostly relying on the selection and improvement of wine yeast strains for reduced ethanol yields. Other possibilities are also presented. Researchers are resorting to both S. cerevisiae and alternative wine yeast species for the lowering of alcohol yields. In addition to the use of selected strains under more or less standard fermentation conditions, aerobic fermentation is increasingly being explored for this purpose. Genetic improvement is also playing a role in the development of biotechnological tools to counter the increase in the wine alcohol levels. The use of recombinant wine yeasts is restricted to research, but its contribution to the advancement of the field is still relevant. Furthermore, genetic improvement by non-GMO approaches is providing some interesting results, and will probably result in the development of commercial yeast strains with a lower alcohol yield in the near future. The optimization of fermentation processes using natural isolates is, anyway, the most probable source of advancement in the short term for the production of wines with lower alcohol contents.

Antioxidant and polyphenol content of different Vitis vinifera seed cultivars and two facilities of production of a functional bakery product

This study aimed to examine the differences between the antioxidant capacity, and the total polyphenol content of the seed of eight different grape varieties. We also attempt to create a functional loaf enriched with grape seed meal. To achieve this goal, 3, 6, and 9% of the grape seed meal were added to the loaves made of bread flour and gluten-free flour mixture, and then the changes in their antioxidant and polyphenol content were examined. Based on the results, there were significant differences between the polyphenol and antioxidant content of grape seed varieties. The antioxidant content of the grape seeds varied between 228.50 mg AAE/g (94.80 mg TE/g) and 438.33 mg AAE/g (181.86 mg TE/g) in case of fatty samples, and between 176.29 mg AAE/g (41.24 mg TE/g) and 424.91 mg AAE/g (99.40 mg TE/g) in case of defatted samples. The total polyphenol content of the fatty samples changed between 91.16 and 221.81 mg GAE/g; in case of defatted samples, it ranged from 46.01 to 207.68 mg GAE/g. Rhine Riesling contained the greatest amount of these compounds. The functionality of loafs was confirmed by spectrophotometric analysis. Total polyphenol content ranged from 0.91 to 3.16 mg GAE/g in case of wheat loafs, and from 1.39 to 5.92 mg GAE/g in case of gluten-free loafs, while the total antioxidant content changed between 0.70 and 6.44 mg AAE/g in case of wheat loafs, and ranged from 2.55 to 9.75 in case of gluten-free loafs.Graphic abstract

Physicochemical and sensory properties of grape juices produced from different cultivars and extraction systems

The objective of the present study was to evaluate grape juices from different cultivars obtained by two different technologies: steam juicer system (S1) and enzymatic system (S2). The beverages were evaluated for physicochemical and sensory characteristics and their adequacy to the identity and quality standards of whole grape juice. Experiments were carried out in the 2018 and 2019 harvests with the grape cultivars BRS Rúbea (RUB), BRS Cora (COR), BRS Violeta (VIO), BRS Carmem (CAR), BRS Magna (MAG), Bordô (BOR), Isabel (ISA), Isabel Precoce (IP), Concord (CON), Concord Clone 30 (C30) and SCS 421 Paulina (SCSP). Treatments followed factorial design (cultivars x extraction system). S1 resulted in juices with lower soluble solids content; on average, a reduction of 3.12 °Brix in 2018 and 2.30 °Brix compared with the original content in grapes. Among S1 juices, only VIO and MAG in 2018, and VIO and CAR in 2019 achieved the minimum value of soluble solids (14 °Brix) established by the Brazilian legislation. Juices of SCSP and CON in 2018 and C30, CON and RUB in 2019 presented values lower than 14 °Brix, independent of the extraction system. S2 juices were characterized by higher values of total acidity, soluble solids, reducing sugars, anthocyanins, global impression, and equilibrium, as well as lower values of lightness for most of the cultivars.

Study on resveratrol content in grapes and wine products

The current state of the agro-industrial complex and the food industry allows to satisfy the needs of various consumers groups. Among those needs, functional foods enriched with beneficial nutrients are becoming more and more popular. Polyphenols are sometimes used as such additives. The bioflavonoid resveratrol, among the group of polyphenols, has very promising antioxidant, therapeutic, antimicrobial properties. In this regard, studying the potential of its use in the food is highly relevant. Resveratrol is naturally present in the dark grapes. It is localized in the skin of the fruit and passes into the food substance during technological processing. This transition has its own patterns which are outlined in this article. Three varieties of grapes were chosen as the objects of the study: Cabernet Sauvignon, Merlot, Krasnostop. Clarified musts from these grape varieties, concentrated musts and wines were researched. High performance liquid chromatography (HPLC) was utilized as the research method. This method allows to separate liquids of complex composition into components with subsequent identification of the mixture composition. To calibrate the chromatograph, the standard “25 mg European Pharmacopoeia”, produced in France, was used as a standard for the pure substance of resveratrol. As the result of the study, it was found that resveratrol is present in the studied samples in various amounts from 4,4 to 7,0 mg / dm³ in the grape juice, from 6,9 to 12,6 mg/dm³ in the wine materials, from 12,4 to 21,3 mg / dm³ in the concentrated juice. These data help establishing the influence of the processing technology of wine and juice concentrates on the resveratrol content. The article also discusses the potential of using concentrated grape juice, rich in resveratrol, to obtain various food products.

The Impact of Early Basal Leaf Removal at Different Sides of the Canopy on Aglianico Grape Quality

It is known that early removal of basal leaves improves the exposure of cluster to direct sunlight and UV radiation, which positively influence the phenolic compounds and anthocyanin concentration of berries. This study was carried out to evaluate the effect of leaf removal applied before flowering to the basal zone of the canopy at different sides (fruit-zone north canopy side, south canopy side and north–south canopy side, respectively) of Aglianico vines trained to vertical shoot position system and row oriented to east–west (EW). The study was conducted in the controlled and guaranteed designation of origin (CGDO) Castel del Monte area (Apulia region, Italy). The treatment did not affect yield per vine, and nor sugar, pH, and total acidity of grapes. When it was applied to the basal south canopy side, the concentration of proanthocyanidins and total polyphenols of grapes increased, as well as antioxidant activity. In particular, anthocyanins content, determined by HPLC, increased by 20% with respect to control when treatment was applied to south and north–south canopy sides. Interaction between season period and treatment was found for all anthocyanins except for petunidin-3-coumaroyl-glucoside. Basal leaf removal applied to the north canopy side caused an increase in malvidin-3-O-glucoside content in grapes in 2016 and 2018, but not in 2017. Our results indicate that basal leaf removal (six basal leaves removed from the base of the shoots) before flowering (BBCH 57) can be used as an effective strategy to improve grape total polyphenols, anthocyanins concentration and antioxidant activity in vineyards cultivated under warm climate conditions. The treatment could represent a sustainable alternative to manual cluster thinning since it does not reduce yield per vine and can be performed mechanically.

Influence of seaweed foliar application to Tempranillo grapevines on grape and wine phenolic compounds over two vintages

The study of seaweeds is increasing in viticulture due to their implications on plant protection and grape quality. This trial aimed to study the effects of foliar applications of an Ascophyllum nodosum extract at low (0.25%, v v−1) and high (0.50%, v v−1) dosages on grape and wine phenolic compounds in 2017 and 2018. In grapes, seaweed biostimulation increased the content of malvidin-3-glc, myricetin-3-glc and myricetin-3-gal in 2017 season. Moreover, both treatments improved the synthesis of trans-piceid and total stilbenes in both seasons. Sensory analysis revealed that 2017 wines had more color than the 2018 wines, which coincided with color intensity parameters. Therefore, seaweed applications to grapevines improved stilbenes content in grapes independently of the season and its effects on the rest of phenolic compounds in grapes and wines depended strongly of season factor.