 IVES 9 IVES Conference Series 9 Enzyme treatments during pre-fermentative maceration of white winegrapes: effect on volatile organic compounds and chromatic traits

Enzyme treatments during pre-fermentative maceration of white winegrapes: effect on volatile organic compounds and chromatic traits

Abstract

AIM: Volatile organic compounds (VOCs) are very important for the characterisation and quality of the final white wine. An oenological practice to increase the extraction of aroma compounds is the cold pre-fermentative maceration [1,2], although it may also release phenolic compounds that confer darker chromatic traits to white wines, not appreciated by consumers. This practice could be improved by the use of enzymes in order to facilitate the release of the odorous molecules. In this study, the effect of different enzyme treatments during skin contact on the chromatic characteristics and volatile composition of white musts from four winegrape varieties was evaluated.

METHODS: Different enzymes presenting distinct single activities (pectolytic and non pectolytic) were added to the must of four white winegrape varieties (Arneis, Greco, Falanghina and Chardonnay) and then subjected to cold pre-fermentative maceration. For each enzyme and variety tested, three berry replicates of 500 g each were randomly selected, added with 10 mg/kg of potassium metabisulphite and crushed. Enzymes were added at a dose of 10 mg/kg. Then, the must was left in contact with the skins for 13 h at 12 °C. Furthermore, other three berry replicates of 500 g each were used as control following the same procedure without enzyme addition. At the end, the musts obtained were separated from the skins and analysed for total polyphenolic index (TPI), chromatic parameters (absorbance at 420 nm and CIELab coordinates), as well as free and glycosylated VOCs. Volatile composition was determined by solid-phase extraction followed by GC-MS analysis [3].

RESULTS: The use of enzymes during cold pre-fermentative maceration resulted in musts having different technological parameters, such as must yield, pH and organic acids content. The chromatic characteristics related to yellow/brown colour (absorbance at 420 nm and CIELab coordinates) and TPI values were dependent on the enzyme used. Indeed, pectin lyase, polygalacturonase and arabinase reduced the yellow colour component of the must obtained when compared to the control sample. Regarding VOCs, different enzymes modulated the release of free forms differently, which are olfactively perceptible, but also they increased the extraction of glycosylated compounds into the grape must. Particularly, most of enzymes tested had a positive effect on the release of terpenes, however the release of norisoprenoids, C6 compounds, alcohols and benzenoids was influenced by both the enzyme used and the variety treated

CONCLUSIONS: The use of different enzymes influenced technological parameters, chromatic characteristics and VOCs contents but some effects were variety dependent. This study may aid oenologists to better understand the action of these enzymes and thus to manage cold pre-fermentative maceration according to the oenological objective.

DOI:

Publication date: September 27, 2021

Issue: Macrowine 2021

Type: Article

Authors

Mattia Malabaila, Stefano BOZ, Maria Alessandra PAISSONI, Carlo MONTANINI, Simone GIACOSA, Luca ROLLE, Susana RÍO SEGADE,

University of Torino, Italy.

Contact the author

Keywords

enzymes, pre-fermentative maceration, volatile organic compounds, chromatic characteristics, white winegrapes

Citation

An analytical framework to site-specifically study climate influence on grapevine involving the functional and Bayesian exploration of farm data time series synchronized using an eGDD thermal index

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Effect of partial net shading on the temperature and radiation in the grapevine canopy, consequences on the grape quality of cv. Gros Manseng in PDO Pacherenc-du-vic-Bilh

As elsewhere, southwestern France vineyards face more recurrent summer heat waves these last years. Among the possibilities of adaptation to this climate changing parameter, the use of net shading is a technique that allow for limiting canopy exposure to radiations. In this trial, we tested net shading installed on one face of the canopy, on a north-south row-oriented plot of cv. Gros Manseng trained on VSP system in the PDO Pacherenc-du-Vic-Bilh. The purpose was to characterize the effects on the ambient canopy temperatures and radiations during the season and to observe the consequences on the composition of grapes and wines. Two sorts of net were used with two levels of obstruction (50% and 75%) of the photosynthesis active radiation (PAR). They have been installed on the west side of the canopy and compared to a netless control. Temperature and PAR sensors registered hourly data during the season. On specific summer day (hot and sunny) manual measurements took also place on bunches (temperature) and in different spots of the canopy (PAR). The results showed that, on clear days, the radiation is lowered by the shade nets respecting the supplier criteria. The effects on the ambient canopy temperature were inconstant on this plot when we observed the data from the global period of shading between fruit set and harvest. However, during hot days (>30°C), the temperature in the canopy was reduced during afternoon and the temperature of the bunch surface was reduced as well comparing to the control. A decrease of the maturity parameters of the berries, sugar and acidity, was also observed. Concerning the wine aromatic potential, no differences clearly appeared.

Adapting the vineyard to climate change in warm climate regions with cultural practices

Since the 1980s global regime shift, grape growers have been steadily adapting to a changing climate. These adaptations have preserved the region-climate-cultivar rapports that have established the global trade of wine with lucrative economic benefits since the middle of 17th century. The advent of using fractions of crop and actual evapotranspiration replacement in vineyards with the use of supplemental irrigation has furthered the adaptation of wine grape cultivation. The shift in trellis systems, as well as pruning methods from positioned shoot systems to sprawling canopies, as well as adapting the bearing surface from head-trained, cane-pruned to cordon-trained, spur-pruned systems have also aided in the adaptation of grapevine to warmer temperatures. In warm climates, the use of shade cloth or over-head shade films not only have aided in arresting the damage of heat waves, but also identified opportunities to reduce the evapotranspiration from vineyards, reducing environmental footprint of vineyard. Our increase in knowledge on how best to understand the response of grapevine to climate change was aided with the identification of solar radiation exposure biomarker that is now used for phenotyping cultivars in their adaptability to harsh environments. Using fruit-based metrics such as sugar-flavonoid relationships were shown to be better indicators of losses in berry integrity associated with a warming climate, rather than solely focusing on region-climate-cultivar rapports. The resilience of wine grape was further enhanced by exploitation of rootstock × scion combinations that can resist untoward droughts and warm temperatures by making more resilient grapevine combinations. Our understanding of soil-plant-atmosphere continuum in the vineyard has increased within the last 50 years in such a manner that growers are able to use no-till systems with the aid of arbuscular mycorrhiza fungi inoculation with permanent cover cropping making the vineyard more resilient to droughts and heat waves. In premium wine grape regions viticulture has successfully adapted to a rapidly changing climate thus far, but berry based metrics are raising a concern that we may be approaching a tipping point.

The impact of sustainable management regimes on amino acid profiles in grape juice, grape skin flavonoids, and hydroxycinnamic acids

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Local adaptation tools to ensure the viticultural sustainability in a changing climate

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