Impact of environmental conditions in vscs production during wine fermentation by Saccharomyces cerevisiae

The advent of precision viticulture (PV) has allowed to address problems related to spatial and temporal variability at the within-field scale. Nowadays, several remote and proximal sensing solutions allow description of the existing variability at different temporal and ground resolution through extremely robust soil, vigor, yield, and grape quality maps. In parallel, numerous studies have described grapevine performances within the homogeneous zones and identified soil as main driver of variability. There is a broad consensus that different vigor zones within the same plot may show differential canopy growth, yield and fruit composition, depicting diverse enological potentials and cultural needs.

Developments in high-throughput sequencing (HTS) technologies allow us to obtain large amounts of microbial information from wine and must samples. Thus approaches, that are aimed at characterising the microbial diversity during fermentation, can be enhanced, or possibly even replaced, with HTS-based metabarcoding. To reduce experimental biases and increase data reproducibility, we compared 3 DNA extraction methods by evaluating differences in the fungal diversity with Riesling alcoholic fermentation samples at four different vineyards. The fungal diversity profiling was done using the genetic markers ITS2 and D2 using metabarcoding. The extraction methods compared consisted of a commercial kit, a recently published protocol that includes a DNA enhancer, and a protocol based on a buffer containing common inhibitor removal reagents. All methods were able to distinguish vineyard effects on the fungal diversity, but the results differed quantitatively.

Protein haze in white wines is a major technological and economic problem of the wine industry. Field tests were carried out in steep slope vineyards planted with Riesling grapes over 3 dry growing seasons to study the effect of drought stress on the concentration of proteins in the resulting wines. Plots suffering from drought stress were compared with surrounding drip irrigated plots. Riesling grapes were processed into wines by conventional procedures. Protein amounts of the isolated wine colloids of the stressed samples were always higher than those of the watered samples(mean watered 13.8 ± 0.44, mean stressed 17.4 ± 0.40 g 100 g-1). As a consequence, higher bentonite doses were needed to achieve protein haze stability of the drought stressed treatments.

Climate change poses several challenges for the wine-industry in the 21st century. Adaptation of viticultural and winemaking practices are therefore essential to preserve wine quality and typicity. Given the complex interactions between physical, biological and human factors at terroir scales, studies conducted at these fine scales allow to better define the local environment and its influences on grapevine growth and berry ripening.

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