A new method of protein extraction from red wines

Abstract

<p style="text-align: justify;"><strong>Aim</strong>: Wine is a very complex medium and is often evaluated according to its main components like alcohol, sugar, tannins, and acid levels. Proteins are rarely considered in this evaluation because their concentrations are only a few mg/L of wine. However, in an enological context, proteins appear to be more and more important, in particular for the stability of wines with protein haze problems. The study of proteins is less obvious in red wines than in white wines because the proteins are strongly tied to tannins, which makes their extraction and analysis even more difficult.</p><p style="text-align: justify;"><strong>Methods and results</strong>: This article describes a technique for the separation of proteins from tannins thanks to a methanol/chloroform emulsion in an acid solution. The protein extract, obtained after 4 hours, was later analyzed by SDS-Page and the protein profile of the wine established. Experiments showed that the protein profiles remained the same during the different stages of the winemaking process, whereas the overall amount of proteins decreased. Characteristic protein profiles of different grape varieties were established, and it was also possible to visualize the presence of exogenous proteins from fining agents like albumin and casein.</p><p style="text-align: justify;"><strong>Conclusion</strong>: This procedure allowed the extraction of proteins from 8 red wine samples within 4 hours. It also made it possible to analyze the extracted proteins by SDS-Page without tannin interference within 2 hours.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This method shows in a very promising manner how proteins might be extracted from red wines after being separated from their tannins. The extracted proteins are then available for analysis using even more advanced techniques such as ESI-QTof or ELISA.</p>

Retention of Proanthocyanidin in Wine-like Solution Is Conferred by a Dynamic Interaction between Soluble and Insoluble Grape Cell Wall Components

“…To our knowledge, the work on non- vinfera grape varieties, and some vinifera varieties, was the first to quantify this effect in red wines . On the other hand, various studies have reported the presence of protein in soluble complexes with PA , and in the case of Shiraz (Syrah) proteins corresponding to the molecular weight of PR-proteins are notably absent . Together with our results, these observations provide evidence that a fraction of PA is likely to be removed from vinifera red wines and that this effect is quantitatively much smaller compared to certain non- vinifera varieties, which contain naturally high levels of PR-proteins .…”

“…A natural conclusion from their study, and the data presented here is that albeit at far lower protein concentrations, red vinifera varieties may resent PA losses via precipitation with proteins during crushing and winemaking. This also might account for the generally low levels of grape-derived PR protein recovered in finished red vinifera wines, which for Shiraz in particular are <2 μg/mL . The potential for grape-derived proteins to fine PA during the winemaking and aging process has been suggested historically, , but studies confirming that the phenomenon exists in vinifera red grapes and wines are lacking.…”

Effect of the Addition of Non-Saccharomyces at First Alcoholic Fermentation on the Enological Characteristics of Cava Wines

“…Protein quantification was performed using a UV-visible spectrophotometer (BioDrop µLite, from Thermo Fisher Scientific, Waltham, MA, USA) for micro sample volumes. For measurement and quantification, all of the protein powder extracted from 16 mL of wine sample according to the preparation described by Silvestri et al [14] was used. Thus, 40 µL of 0.16 M TRIS-HCL (pH 6.8) was added to the protein powder in a 1.5 mL tube and then placed in an ultrasound bath for 60 min at 50 • C. The measurement of the absorbance of the proteins was carried out at 280 nm using 3 µL of sample.…”

“…Samples of base wines were analyzed by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) (Figure S1). A previous sample extraction treatment was carried out, which was used both for its quantification by UV and for gel electrophoresis, as described by Silvestri et al [14]. The proteins of the extracted wine samples were separated using SDS-PAGE (15% resolving gel and 5% stacking gel) in a vertical electrophoresis unit with an applied voltage of 100 V. The marker used was Precision Plus Protein™ Dual color Standards (Bio-Rad, Hercules, CA, USA).…”