OENO IVAS 2019 banner
IVES 9 IVES Conference Series 9 Importance of matrix effects (wine composition) on protein stability tests of white and rosé wines

Importance of matrix effects (wine composition) on protein stability tests of white and rosé wines


The presence of unstable proteins in wines can affect their stability and clarity. Before bottling, winemakers need to be sure that the wine is stable. A large number of stability tests have been proposed, usually based on heating a sample with a specific time-temperature couple. In practice, none is effective to accurately assess the risk of instability. Moreover, the interpretation of the results of these tests changes according to the region. 

The aim of this work is to compare, on 55 wines (4 vintages, 7 varieties, 5 areas), the most common heat test (30 minutes at 80°C) with the turbidity measured after 15 days at 35 °C on bottled wines. Proteins were analyzed in 33 cases. In addition, 10 wines were heated at 40 °C/30 min, 40°C/4 hours, 35 °C/15 days and 80 °C/30 min and the residual proteins analyzed. 

The results show no correlation between turbidity after heat test 80 °C/30 min and after 15 days at 35 °C. For some wines, especially Gewurztraminer ones, turbidity after heating at 80 °C can reach 330 NTU without any visual haze at 35 °C (< 3 NTU). Similar results are obtained when the heat test is performed after adjustment of pH to 3.4. The turbidity after heat test 80°C/30 min increases with pH, particularly above 3.6, which is not so unusual for Gewurztraminer wines. The pH effect is less significant at 40 °C. Finally, pH values alone cannot explain the different behaviors of wines. 

On the other hand, protein composition in wines depends on their pH. Thaumatin Like proteins (TL) 19 kDa, TL 22kDa and Invertases are present in almost all wines. Half of them contains Lipid Transfer Protein (LTP) and only a few Chitinases and β-Glucanase. These proteins are present when pH is lower than 3.5, probably because low pH favor Chitinase and-glucanase conformational changes and precipitation. 

Protein analysis after heating these various wines at different time-temperature couples led to this ranking: 
Chitinases are sensitive at low temperature (40 °C) and resist better at pH 3.7; 
TL 22kDa are sensitive, especially in Rosé wines; 
TL 19kDa are more stable, but their sensitivity depends on the pH; 
Invertase unfold between 60 and 80°C but is not affected by the pH; 
LTP can resist up to 80 °C. 

Turbidity after usual heat test 80 °C/30 min increases with total proteins concentration and pH. This is not observed after 15 days at 35 °C or 4 hours at 40 °C. These tests may be better to evaluate the actual risk of instability after bottling.

Related articles…

The development of a simple electrochemical method based on molecularly imprinted polymers for the selective determination of caffeic acid in wine

Caffeic acid (CA) is an antioxidant of great importance in the food sector, such as wine, where it acts as a marker of wine ageing, as well as in the health sector due to its antioxidant properties and beneficial effects including the prevention of inflammation, cancer, neurodegenerative diseases, and diabetes.


Grape volatile compounds are mainly responsible for wine aroma, so it is important to know the va-rietal aromatic composition throughout ripening process. Currently, there are no tools that allow mea-suring the aromatic composition of grapes, in intact berries and periodically, throughout ripening, in the vineyard or in the winery. For this reason, this work evaluated the use of near infrared spectroscopy (NIR) to estimate the aromatic composition and total soluble solids (TSS) of Tempranillo Blanco berries during ripening. For this purpose, NIR spectra (1100-2100 nm) were acquired from 240 samples of in-tact berries, collected at different dates, from veraison to overripening.

Influence of the temperature of the prise de mousse on the effervescence and foam of Champagne and sparkling wines.

The persistence of effervescence and foam collar during a Champagne or sparkling wine tasting constitute one, among others, specific consumer preference for these products. Many different factors related to the product or to the tasting conditions might influence their behavior in the glass


The exploitation of secondary metabolic pathways of non-Saccharomyces yeasts is a promising approach to protect traditional wines from the ongoing climate change, which can alter their peculiar features by modifying the chemical composition of grape musts. In this regard, an interesting example is the sequential inoculum of Lachancea thermotolerans and Saccharomyces. Cerevisiae. The aim of the sequential inoculum is to increase titratable acidity by lactic acid accumulation, to lower pH and to reduce the alcohol and acetic acid content in wine.

Identification of loci associated with specialised metabolites in Vitis vinifera

Secondary (or specialised) metabolites such as terpenes and phenolic compounds are produced by plants for various roles which include defence against pathogens and herbivores, protection against abiotic stress, and plant signalling. Additionally, these metabolites influence grapevine quality traits such as colour, aroma, taste, and nutritional value. However, the biosynthesis of these metabolites is often complex and controlled by multiple genes which in grapevine are predominantly uncharacterised.