OENO IVAS 2019 banner
IVES 9 IVES Conference Series 9 The affinity of white wine proteins for bentonite is dependent on wine composition and is directly related to their thermal stability / sensitivity

The affinity of white wine proteins for bentonite is dependent on wine composition and is directly related to their thermal stability / sensitivity

Abstract

Bentonite fining is commonly used in oenology to remove all or parts of white wine proteins, which are known to be involved in haze formation. This fining is effective, but has disadvantages: it is not selective, thus molecules responsible for aroma are also removed, it causes substantial volume losses, and finally it generates wastes. Over the last decades, the knowledge of wine proteins has increased: they have been identified, their structures are known, some of them have been crystallized. 

However, haze formation is not only a question of protein composition and concentration. It depends on many other factors, such as pH, wine composition (polyphenols, polysaccharides,…). Heat or chemical tests used to adjust the bentonite dose often leads to an overestimation, because they aim at removing all the proteins, even the ones that are stable in the range 60-80 °C and are not involved in spontaneous haze. 

In this study, we analyzed and quantified the proteins in 7 white wines (3 varieties, 4 areas), treated with four bentonite doses ranging from 5 to 80 g/hL. In parallel, samples of wines were heated during 30 minutes at 40, 60 and 80 °C and the residual proteins analyzed. 

The wines differed in their protein composition. In each wine, when they were present, the proteins were adsorbed on bentonite in this order: chitinase and β-glucanase, Lipid Transfer Protein (LTP), Thaumatin Like (TL) 22 kDa, TL 19 kDa and Invertase. 

The adsorption of a given protein was wine dependent. This could be due to wine pH and ionic strength (different in the studied wines), which changes electrostatic interactions that drive the protein adsorption onto bentonite, but also to other differences in composition (ethanol, polysaccharides, polyphenols, metals…). Experiments performed at pH 2.5 indicated that pH is not the only cause of such different adsorption behaviours: indeed adsorption isotherms were different. 

Protein adsorption on bentonite was compared to their thermal sensitivity. It was ranked as previously: β-glucanase ~ Chitinase > TL22 > TL19 ~ Invertase > LTP. It is worth noting that the most thermostable proteins are the ones which need the highest doses of bentonite on a wide panel of wines. These stable proteins do not need to be removed and thus bentonite doses could be reduced. More specific tests, which would take into account only the most sensitive proteins need to be developed.

DOI:

Publication date: June 23, 2020

Issue: OENO IVAS 2019

Type: Article

Authors

Céline Poncet-Legrand (1), Eric Meistermann (2), Frédéric Charrier (3), Philippe Cottereau (4), Patrick Chemardin (1), Aude Vernhet (1)

1 UMR SPO- Univ Montpellier – INRA- Montpellier SupAgro – 2, place Pierre Viala, 34060 Montpellier cedex FRANCE 
2 Institut Français de la Vigne et du Vin, F-68000 Colmar 
3 Institut Français de la Vigne et du Vin, F-44120 Vertou 
4 Institut Français de la Vigne et du Vin, F-30230 Rodilhan 

Contact the author

Keywords

haze formation, fining, protein adsorption, wine matrix

Tags

IVES Conference Series | OENO IVAS 2019

Citation

Related articles…

Mapping and tracking canopy size with VitiCanopy

Understanding vineyard variability to target management strategies, apply inputs efficiently and deliver consistent grape quality to the winery is essential. However, despite inherent vineyard variability, the majority are managed as if they are uniform. VitiCanopy is a simple, grower-friendly tool for precision/digital viticulture that allows users to collect and interpret objective spatial information about vineyard performance. After four years of field and market research, an upgraded VitiCanopy has been created to achieve a more streamlined, technology-assisted vine monitoring tool that provides users with a set of superior new features, which could significantly improve the way users monitor their grapevines. These new features include: • New user interface • User authentication • Batch analysis of multiple images • Ease the learning curve through enhanced help features • Reporting via the creation of colour maps that will allow users to assess the spatial differences in canopies within a vineyard. Use-case examples are presented to demonstrate the quantification and mapping of vineyard variability through objective canopy measurements, ground-truthing of remotely sensed measurements, monitoring of crop conditions, implementation of disease and water management decisions as well as creating a history of each site to forecast quality. This intelligent tool allows users to manage grapevines and make informed management choices to achieve the desired production targets and remain profitable.

Aromatic maturity is a cornerstone of terroir expression in red wine

Harvesting grapes at adequate maturity is key to the production of high-quality red wines. Enologists and wine makers define several types of maturity, including technical maturity, phenolic maturity and aromatic maturity. Technical maturity and phenolic maturity are relatively well documented in the scientific literature, while articles on aromatic maturity are scarcer. This is surprising, because aromatic maturity is, without a doubt, the most important of the three in determining wine quality and typicity (including terroir expression). Optimal terroir expression can be obtained when the different types of maturity are reached at the same time, or within a short time frame. This is more likely to occur when the ripening takes place under mild temperatures, neither too cool, nor too hot. Aromatic expression in wine can be driven, from low to high maturity, by green, herbal, fresh fruit, ripe fruit, jammy fruit, candied fruit or cooked fruit aromas. Green and cooked fruit aromas are not desirable in red wines, while the levels of other aromatic compounds contribute to the typicity of the wine in relation to its origin. Wines produced in cool climates, or on cool soils in temperate climates, are likely to express herbal or fresh fruit aromas; while wines produced under warm climates, or on warm soils in temperate climates, may express ripe fruit, jammy fruit or candied fruit aromas. Growers can optimize terroir expression through their choice of grapevine variety. Early ripening varieties perform better in cool climates and late ripening varieties in warm climates. Additionally, maturity can be advanced or delayed by different canopy management practices or training systems.

Analysis of Cabernet Sauvignon and Aglianico winegrape (V. vinifera L.) responses to different pedo-climatic environments in southern Italy

Water deficit is one of the most important effects of climate change able to affect agricultural sectors. In general, it determines a reduction in biomass production, and for some plants, as in the case of grapevine, it can endorse fruit quality. The monitoring and management of plant water stress in the vineyard

Effects of organic mulches on the soil environment and yield of grapevine

Farming management practices aiming at conserving soil moisture have been developed in arid and semiarid-areas facing water scarcity problems. Organic mulching is an effective method to manipulate the crop-growing microclimate increasing crop yield by controlling soil temperature, and retaining soil moisture by reducing soil evaporation. In this sense, the effectiveness of different organic mulching materials (straw mulch and grapevine pruning debris) applied within the row of a vineyard was evaluated on the soil and on the vine in a Tempranillo vineyard located in La Rioja (Spain). Organic mulches were compared with a traditional bare soil management technique (based on the use of herbicides to avoid weed incidence). Mulching coverages favourably influenced the soil water retention throughout all the grapevine vegetative cycle. However, the soil-moisture variation was not the same under different mulching materials, being the straw mulch (SM) the one that retained more water in comparison with grapevine pruning debris (GPD) based-cover. The changes of soil moisture in the upper surface layer (0–10 cm) were highly dynamic, probably due to water vapour fluxes across the soil-atmospheric interface. However, both, SM and GPD reduced these fluctuations as compared with bare soils. A similar trend occurred with soil temperature. Both organic mulches altered soil temperature in comparison with bare soil by reducing soil temperature in summer and raising it in winter. Moreover, the same buffering effect for the temperature on the covered soil also remains in the deeper layers. To conclude, we could see that organic mulching had a positive impact on soil-moisture storage and soil temperature and the extent of this effect depends on the type of mulching materials. These changes led to higher rates of photosynthesis and stomatal conductivity compared to bare soils, also favouring crop growth and grape yields.

δ13C : A still underused indicator in precision viticulture  

The first demonstration of the interest of carbon isotope composition of sugars in grapevine, as an integrated indicator of vineyard water status, dates back to 2000 (Gaudillère et al., 1999; Van Leeuwen et al., 2001). Thanks to the isotopic discrimination of Carbon that takes place during plant photosynthesis, under hydric stress conditions, it is possible to accurately estimate the photosynthetic activity. Ever since, δ13C has been widely applied with success to zonation, terroir studies and vine physiology research, but is still not widely used by viticulturists. This is quite astonishing by considering the impact of global warming on viticulture and the need to improve water management, that would justify a widespread use of δ13C.
The lack of private laboratories proposing the analysis, the cost of the technology, as well as the long analytical delays, have been detrimental to its development. Some laboratories tried to overcome the analytical difficulties of isotopic analysis by using fourier transformed infrared spectroscopy, as a fast and cheap alternative to the official OIV method (IRMS). These claimed FTIR models have never been published or peer reviewed and cannot be considered robust. In this work, thanks to the recent acquisition of IRMS technology, new modern and robust applications of δ13C for viticulture are proposed. This includes the use of the analysis to make parcel separations at harvesting, the possibility to increase the precision of hydric stress cartography and the potential cost reduction when compared with Scholander pressure bomb analysis.