Acetaldehyde-induced condensation products in red wines affect the precipitation of salivary proteins. Will this impact astringency?

Abstract

Acetaldehyde is a common component of wine. It is already formed during the fermentation being an intermediate in the production of ethanol. Moreover, it can derive from the oxidation of ethanol during the wine production and aging. In wine, concentrations of acetaldehyde range from 30 to 130 mg/L. Acetaldehyde in wine can react with many compounds such as SO2, amino acids and polyphenols. The reaction between acetaldehyde and wine polyphenols takes place through a nucleophilic attack of polyphenols on the protonated form of the aldehyde,  affording methyl methine-linked dimers of two different units of polyphenolic structures, among others. The numerous and complex reactions trigged by acetaldehyde markedly influence the evolution of red wines during aging. Although numerous studies aimed to determine the chemical nature of reaction products in model solution and real wines, data concerning a possible change in reactivity of red wines towards salivary proteins due to acetaldehyde reactions are not known. This piece of information can be of great relevance as the interaction of wine with saliva and the precipitation of salivary proteins is a major phenomenon responsible for wine astringency. 

In the present work, to investigate the changes in the precipitation of salivary proteins after interaction with red wine, the effects of increasing concentrations of acetaldehyde (0-190 mg/L) in two wines with different polyphenolic composition (Aglianico and Tintilia) were studied over a 90-day period.

The impact of acetaldehyde reactions on the reactivity towards salivary proteins was determined by SDS-PAGE analysis of proteins before and after the reaction and Saliva Precipitation Index (SPI) was measured. 

For both wines a significant precipitation of colored matter was observed as a function of acetaldehyde concentration.  In all wines, a decrease of SPI due to acetaldehyde addition was detected. However, a different trend was observed in the two wines. In particular, Aglianico showed a greater decrease. The SPI of either Aglianico or Tintilia significantly changed over time along with polymeric pigments content as suggested by HPLC and MS analyses.

Overall, the results showed that the reactions in which acetaldehyde is involved exert important effects in the interactions between polyphenolic compounds and salivary proteins.

Therefore, the management of the acetaldehyde is to be properly addressed throughout all the stages of the winemaking process.