LAUSR

Protein-polyphenol interactions play a very important role in wine stability assessment, especially in red varieties. Different polysaccharides can influence these interactions by protecting or disrupting charges and are even used as additives to stabilize colloidal solutions. The most common examples are mannoproteins and carboxymethyl cellulose (CMC). In some cases, the mechanisms that are involved in these reactions are not thoroughly understood and can lead to unexpected problems and delayed haze formation after CMC addition to red wines. Small scale bench-trials were conducted in model systems under different pH-conditions to monitor the formation of turbidity and protection mechanisms during the interaction of proteins, polyphenols, and polysaccharides. Egg-white protein was chosen as a protein model due to its complex composition, a commercial grape tannin extract was used as polyphenol source, and pectin, glucomannan, mannoprotein, alginate, and CMC were applied as polysaccharides to model various wine conditions. Reactions were monitored in duplicate on a 50 mL scale by spectrophotometry at 860 nm over at least 30 days. Some of the polysaccharides interacted directly with proteins or polyphenols causing precipitation. Other polysaccharides delayed the reaction between proteins and other macromolecules depending on their concentration. The results of these experiments provide important insight into reaction dynamics between macromolecules that are involved in the physical stability of wine.