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Effects of Traditional and Modern Post-Harvest Withering Processes on the Composition of the Vitis v. Corvina Grape and the Sensory Profile of Amarone Wines.

ABSTRACT: In the Valpolicella area (Verona, Italy) Vitis vinifera cv. Corvina is the main grape variety used to produce Amarone wine. Before starting the winemaking process, the Corvina grapes are stored in a withering (i.e., dehydrating) warehouse until about 30% of the berry weight is lost (WL). This practice is performed to concentrate the metabolites in the berry and enrich the Amarone wine in aroma and antioxidant compounds. In compliance with the guidelines and strict Amarone protocol set by the Consorzio of Amarone Valpolicella, withering must be carried out by setting the grapes in a suitable environment, either under controlled relative air humidity (RH) conditions and wind speed (WS)-no temperature modification is to be applied-or, following the traditional methods, in non-controlled environmental conditions. In general, the two processes have different dehydration kinetics due to the different conditions in terms of temperature, RH, and WS, which affect the accumulation of sugars and organic acids and the biosynthesis of secondary metabolites such as stilbenes and glycoside aroma precursors. For this study, the two grape-withering processes were carried out under controlled (C) and non-controlled (NC) conditions, and the final compositions of the Corvina dried grapes were compared also to evaluate the effects on the organoleptic characteristics of Amarone wine. The findings highlighted differences between the two processes mainly in terms of the secondary metabolites of the dried grapes, which affect the organoleptic characteristics of Amarone wine. Indeed, by the sensory evaluation, wines produced by adopting the NC process were found more harmonious, elegant, and balanced. Finally, we can state how using a traditional system, grapes were characterised by higher levels of VOCs (volatile compounds), whilst wines had a higher and appreciable complexity and finesse.

SUBMITTER: Tomasi D

PROVIDER: S-EPMC8434166 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Vitis vinifera L. cv. Corvina grape forms the basis for the production of unique wines, such as Amarone, whose distinctive sensory features are strongly linked to the post-harvest grape withering process. Indeed, this process increases sugar concentration and changes must characteristics. While microorganisms involved in must fermentation have been widely investigated, few data are available on the microbiota of withered grapes. Thus, in this paper, a whole metagenome sequencing (WMS) approach was used to analyse the microbial consortium associated with Corvina berries at the end of the withering process performed in two different conditions ("traditional withering," TW or "accelerated withering," AW), and to unveil whether changes of drying parameters could have an impact on microbial diversity. Samples of healthy undamaged berries were collected and washed, to recover microorganisms from the surface and avoid contamination with grapevine genetic material. Isolated DNA was sequenced and the data obtained were analyzed with several bioinformatics methods. The eukaryotic community was mainly composed by members of the phylum Ascomycota, including Eurotiomycetes, Sordariomycetes, and Dothideomycetes. Moreover, the distribution of the genera Aspergillus and Penicillium (class Eurotiomycetes) varied between the withered berry samples. Instead, Botryotinia, Saccharomyces, and other wine technologically useful microorganisms were relatively scarce in both samples. For prokaryotes, 25 phyla were identified, nine of which were common to both conditions. Environmental bacteria belonging to the class Gammaproteobacteria were dominant and, in particular, the TW sample was characterized by members of the family Pseudomonadaceae, while members of the family Enterobacteriaceae dominated the AW sample, in addition to Sphyngobacteria and Clostridia. Finally, the binning procedure discovered 15 putative genomes which dominated the microbial community of the two samples, and included representatives of genera Erwinia, Pantoea, Pseudomonas, Clostridium, Paenibacillus, and of orders Lactobacillales and Actinomycetales. These results provide insights into the microbial consortium of Corvina withered berries and reveal relevant variations attributable to post-harvest withering conditions, underling how WMS could open novel perspectives in the knowledge and management of the withering process of Corvina, with an impact on the winemaking of important Italian wines.

Project description:We applied the RNA-Seq approach to reconstruct the transcriptome of Vitis vinifera cv. Corvina, using RNA pooled from a comprehensive set of sampled tissues in different organs and development steps, and we were able to reconstruct some novel and putative private Corvina genes. We analyzed the expression of these genes in three berry developmental conditions, and posit that they may play some role in the formation of the mature organ. Background: Plants display a high genetic and phenotypic variability among different cultivars. Understanding the genetic components that contribute to phenotypic diversity is necessary to disentangle genetic factors from the environment. Given the high degree of genetic diversity among plant cultivars a whole-genome sequencing and re-annotation of each variety is required but a reliable genome assembly is hindered by the high heterozigosity and sequence divergence. Results: we show the feasibility of an approach based on sequencing of cDNA by RNA-Seq to analyze varietal diversity between a local grape cultivar Corvina and the PN40024 grape reference genome. We detected 15,260 known genes and we annotated alternative splicing isoforms for 9,463 genes. Our approach allowed to define 2,321 protein coding putative novel genes in unannotated or unassembled regions of the reference genome PN40024 and 180 putative private Corvina genes whose sequence is not shared with the reference genome. Conclusions: With a de novo assembly based approach we were able to reconstruct a substantial part of the Corvina transcriptome and we improved substantially known genes annotations by better defining the structure of known genes, annotating splicing isoforms and detecting unannotated genes. Moreover our results clearly define sets of private genes which are likely part of the âdispensableâ genome and potentially involved into influencing some cultivar-specific characteristics. In plant biology a transcriptome de novo assembly approach should not be limited to species where no reference genome is available as it can improve the annotation lead to the identification of genes peculiar of a cultivar.

Dataset Information

Effects of Traditional and Modern Post-Harvest Withering Processes on the Composition of the Vitis v. Corvina Grape and the Sensory Profile of Amarone Wines.

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