Influence of Soil Management on the Red Grapevine (Vitis vinifera L.) Mencía Must Amino Acid Composition and Wine Volatile and Sensory Profiles in a Humid Region

Can Satellite Remote Sensing Assist in the Characterization of Yeasts Related to Biogeographical Origin?

Biogeography is a key concept associated with microbial terroir, which is responsible for the differentiation and uniqueness of wines. One of the factors influencing this microbial terroir is the vegetation, which in turn is influenced by climate, soil, and cultural practices. Remote sensing instruments can provide useful information about vegetation. This study analyses the relationship between NDVI, calculated using Sentinel-2 and Landsat-8 satellite images of different veraison dates, and microbial data obtained in 2015 from 14 commercial (organic and conventional) vineyards belonging to four Designations of Origin (DOs) from Galicia (northwest Spain). Microbial populations in grapes and musts were identified using PCR techniques and confirmed by sequencing. Statistical analyses were made using PCA, CCA, TB-PLS, and correlation analyses. This study confirms that the NDVI is positively correlated with the diversity of yeasts, both in grapes' surface and must samples. Moreover, the results of this study show: (i) Sentinel-2 images, as well as Landsat-8 images, can establish differences in NDVI related to yeast terroir in grapes and musts, as it is the most relevant DO factor, (ii) Sentinel-2 NDVI and yeast biogeography are moderately to strongly correlated, (iii) Sentinel-2 achieved a better delimitation of the DOs than Landsat-8 and can establish more accurate differences in NDVI-yeast terroir correlations, and (iv) a higher NDVI was associated with the yeast biogeographical patterns of the DOs with higher species richness (S) consisting of weakly fermenting yeasts (Hanseniaspora uvarum, Pichia spp., Starmerella bacillaris, and Zygosaccharomyces spp). However, NDVI values did not correlate well with biogeographic patterns of yeasts previously studied at frequency level (proportion or percentage of each species) in each particular DO. This study suggests that satellite imagery has the potential to be a valuable tool for wine quality management and a decision-making instrument for DO regulators and winegrowers.

Integrated Fertilization with Bagasse Vermicompost Changes the Microbiome of Mencía Must and Wine

Winemaking is a well-known process that includes several steps in the production of grape must and wine. Grape marc, or bagasse, is a byproduct of wine production that can be vermicomposted and used as organic fertilizer. Grape marc vermicompost has microbial communities that are richer and more stable than grape marc alone, and its addition to a vineyard’s terroir can improve grape yields and wine quality. Here we compare the must and wine microbiota of Mencía from grapevines treated with and without (standard fertilization) vermicompost derived from Mencía grape marc. Mencía is a high-quality red wine broadly grown in Galicia, Spain, and is appreciated for its fresh acidity and fruity flavors. When Mencía grapevines are treated with vermicompost derived from its grape marc, Mencía vines increase their grape production, and the final wine improves its organoleptic properties. Metataxonomic analyses of the bacterial 16S rRNA and fungal ITS gene regions showed that Mencía must and wine have the distinct taxonomic composition (phyla, genera and ASVs—amplicon sequence variants) of bacterial and fungal groups. Must and wine bacteriotas and mycobiotas show no significant variation in alpha-diversity, while wine bacteriotas and mycobiotas show significant differences in microbial structure (beta-diversity) between treated and control grapevines. Likewise, the functional diversity and predicted metabolic pathways (biosynthesis, degradation/utilization/assimilation, generation of precursor metabolites and energy, macromolecule modification and superpathways) of the must and wine microbiota also show significant changes. Our study proposes that changes in the abundance of microbial taxa and the metabolic processes they undergo during winemaking may improve Mencía’s organoleptic properties and productivity.

Effect of Soil Management and Training System on Negroamaro Wine Aroma

This study aimed to assess the impact of two soil managements and training systems on yield and wine aroma compounds of Negroamaro variety grown in a warm climate region (southern Italy). Cover crop (CC) and soil tillage (ST) as soil management, whilst bilateral Guyot (BG) and monolateral Guyot (MG) as training systems were compared. Free and bound volatile fractions were evaluated by GC-MS. ST and CC as well as BG and MG significantly affected yield parameters. In particular, yield was higher in ST and BG than in CC and MG, respectively; moreover, it was found to be positively influenced by interaction between BG and ST. Regarding aroma compounds, significant interactions between soil management and training system factors were observed. In case of free volatiles, the most positive interaction was found between BG and ST, whereas, for bound volatiles, the best interaction was represented by MG with both soil tillage and cover crop. Vine leaf area and development over vine growth stages along with water stress levels played an important role in determining the aroma profile as well as yield parameters. In conclusion, the training system significantly interacted with soil management and affected most of important aroma compounds in Negroamaro wine.

Terroir Effect on the Phenolic Composition and Chromatic Characteristics of Mencía/Jaen Monovarietal Wines: Bierzo D.O. (Spain) and Dão D.O. (Portugal)

‘Mencía’/‘Jaen’ it’s an important red grape variety, exclusive of the Iberian Peninsula, used in wine production namely in Bierzo D.O. and Dão D.O., respectively. This work evaluates the effect of the two different “terroirs” on the phenolic composition and chromatic characteristics of ‘Mencía’/‘Jaen’ monovarietal wines produced at an industrial scale in the same vintage. Using Principal Component Analysis (PCA), Partial Least Squares-Discrimination Analysis (PLS-DA), and Orthogonal PLS-DA (OPLS-DA) it was found that peonidin-3-coumaroylglucoside, petunidin-3-glucoside, malvidin-3-coumaroylglucoside, peonidin-3-glucoside, malvidin-3-acetylglucoside, malvidin-3-glucoside, and ferulic acid were the phenolic compounds with the highest differences between the two regions. PLS regression allowed to correlate the differences in lightness (L*) and redness (a*) of wines from ‘Jaen’ and ‘Mencía’ to differences in colored anthocyanins, polymeric pigments, total pigments, total anthocyanins, cyanidin-3-acetylglucoside, delphinidin-3-acetylglucoside, delphinidin-3-glucoside, peonidin-3-coumaroylglucoside, petunidin-3-glucoside and malvidin-3-glucoside in wines, and the colorless ferulic, caffeic, and coutaric acids, and ethyl caffeate. The wines a* values were more affected by colored anthocyanins, ferulic acid, total anthocyanins, delphinidin-3-acetylglucoside, delphinidin-3-glucoside and petunidin-3-acetylglucoside, and catechin. The positive influence of ferulic acid in the a* values and ferulic, caffeic, coutaric acids, and ethyl caffeate on the L* values can be due to the co-pigmentation phenomena. The higher dryness and lower temperatures during the September nights in this vintage might explain the differences observed in the anthocyanin content and chromatic characteristics of the wines.

An overview about the impacts of agricultural practices on grape nitrogen composition: Current research approaches

Nitrogen is a structural component of proteins, nucleic acids, chlorophyll, hormones and amino acids. The last one and ammonium are important primary metabolites in grapes and are key compounds in winemaking since they are primary sources for yeast fermentation. Currently, grape quality has been affected due to the negative impacts of global warming and anthropogenic activity. Certain studies have reported a significant decrease in the free amino acids content and an increase in berry soluble solids and in proline biosynthesis in grapes in some grapevine varieties cultivated under warm climate conditions and water restriction. Proline is not metabolized by yeasts and stuck and sluggish fermentations can occur when the content of yeast assimilable nitrogen is low. Nitrogen composition of grape is mainly affected by variety, edaphoclimatic conditions of the vineyard and agricultural practices performed to the grapevines. This review summarized the most current research carried out to modify the nitrogen composition of the grape and give an overview of the technical and scientific aspects that should be considered for future research in this field.

Dynamic of Lachancea thermotolerans Population in Monoculture and Mixed Fermentations: Impact on Wine Characteristics

Lachancea thermotolerans is a non-Saccharomyces yeast appreciated for its potential of acidification due to the production of lactic acid; however, this species also synthetizes other metabolites that modulate organoleptic wine properties. The aim of this study was to evaluate the strain L. thermotolerans Lt93 to ferment ‘Treixadura’ and ‘Mencía’ musts and its impact on yeast population dynamics and wine characteristics. Fermentations using monocultures of L. thermotolerans Lt93 and S. cerevisiae strains, sequential inoculation and spontaneous process were performed. The dynamic of yeast population and wine composition were analyzed following standard methodology. L. thermotolerans Lt93 was unable to overgrow wild yeast population in ‘Treixadura’ white must; however, with ‘Mencía’ red must, Lt93 was the predominant yeast at the beginning of fermentation and remained at high frequency until the end. Lt93 Treixadura wines had slightly higher acidity and higher content of esters and acids than ScXG3 wines. Lt93 Mencía wines presented higher acidity (10.1 g/L) and 0.8% (v/v) lower ethanol content than Sc71B wines. The content of esters and fatty acids was 3.3 and 4.0 times lower, respectively, in Lt93 than in Sc71B Mencía wines. It was possible to increase wine acidity and modulate the chemical wine profile by using Lt93.