Project start: 06.01.2020
Project end: 30.06.2022
Sponsor: German Federation of Industrial Research Associations
The formation of haze in wine and sparkling wine is a major problem of the beverage industry. Due to the climate change and warmer vintages since 1990, the prevalence of haze formation in German wines has increased. Increased protein contents of musts and wines are triggered by drought stress and fungal infections. This causes a higher demand for bentonite as clarification and finishing agent and comes along with losses of wine. Apart from that, quality determining constituents, mainly anthocyanins in red and rosé wines and aroma compounds in white wine may be lost by adsorption to the bentonite. Especially wines from steep slope viticul-ture in Germany are affected by reduced sensory quality caused by high bentonite dosages. Currently, no efficient alternatives to bentonite finishing for removal of haze forming proteins from wine are available. The enzymatic degradation of the protein fraction of wine via commercial peptidases was not successful, which indi-cated unusual stable tertiary structures of wine proteins. The aim of the current research project is to characterize haze forming wine proteins and to develop an efficient enzymatic process to avoid haze formation in wine. The specific degradation of haze causing proteins via novel peptidases (proteases) as alternative to bentonite will be examined. Therefore, a comprehensive screening of peptidases from insects will be performed. Based on successful preliminary studies, research will focus on those insects that feed on grapes (e.g. Drosophila suzukii). A combined method of enzymatic protein degradation with bentonite finishing will be investigated to lower the bentonite consumption. The products of the enzymatic hy-drolysis (peptides and amino acids) will be characterized analytically and their po-tential influence on the sensory properties of wine will be investigated. The stability of peptidase treated musts and wines will be determined in storage trials.