Yeasts protein extracts: sustainable strategy for wine protein stabilization

The yeast proteins extracts (YPEs) are already approved by OIV for the treatment of musts and wines. The YPEs are constituted of complex and heterogeneous mixtures, and their chemical properties can be extremely variable. Several authors reported interesting electric properties of YPE, that can induce possible specific interaction with haze-related wine proteins and a possible use of YPEs as an alternative and more sustainable fining agent against wine protein instabilities. Appropriate analytical methods are fundamental to evaluating their chemical properties and specific effectiveness. The  potential determinations highlighted a negative electric charge of chosen YPE and its potential to interact with PR-proteins. The preliminary trials of YPE addition at 25 and 50 g/hL on unstable Pinot Gris wine allowed a significant decrease of protein instability, measured by the Protein Charge Neutralization test, respectively 22 and 27%. The experimental trials on an unstable Lugana wine, performed with different dosages and treatment times, confirmed the effectiveness of YPE and the results showed potential reversible interaction with haze-related proteins. The YPE addition is significant for times above 4-6 hours, and its effects disappear for longer times. The best results were obtained at 20-30 g/hL of YPE concentration and 4 hours, which induced a 42 % decrease of initial PR-protein concentration (from 165.25  4.18 mg/L to 95.35  6.70 mg/L). The yeast protein extract increased the protein stability of white wines, but it can’t allow their complete stabilization. The addition of YPE could be considered a combined treatment with conventional ones, aimed to decrease the amount of conventional fining agents (e.g bentonite) and mitigate the environmental impact of their disposal. The YPE could represent an alternative treatment focused on the main goals of the circular economy and on more sustainable enology.