The effect of selected fining agents on the composition and quality of Pinot noir wine

Abstract

In recent years there has been considerable debate over the effect various clarifying techniques including fining have on the composition and quality of red wines. The debate seems to be most intense when related to the production of Pinot noir wine.

This study was undertaken to define further the mode of action of proteinaceous fining agents in red wines and to increase our knowledge of what effects these agents have on phenolic compounds in Pinot noir wine. The effect of fresh egg albumin, spray-dried egg albumin, isinglass and gelatin on the phenolic composition and spectral parameters of a Pinot noir wine was investigated.

Spray-dried egg albumin and gelatin were found to significantly reduce the concentration of phenolics including reduction in the concentration of total monomeric anthocyanins and malvidin-3-glucoside. Reduction of colour compounds was reflected by a decrease in the colour density of the wine. A shift in the colour hue towards the red spectrum was not observed. Gelatin fining also decreased the concentration of catechin, epicatechin, procyanidins and gallic acid. Spray dried egg albumin decreased the concentrations of epicatechin, and caftaric acid.

Isinglass and fresh egg albumin did not significantly reduce the phenolic concentration of the wine both displayed a significant effect on the colour density of the wine. This corresponded to a decrease in perceived visible wine colour. Neither isinglass nor fresh egg albumin reduced the monomeric anthocyanin concentration of the wine. It is suggested that decreased colour density may be due to an increase in wine clarity.

In all fining treatments, the final protein concentration of the wines was increased. Fining with fresh egg albumin gave a maximum concentration of 42 mg/L of residual ovalbumin. Elevated ovalbumin concentration in wine may decrease the perceived astringency and bitterness of wine. The inability of spray dried albumin to display these characteristics is related to its partial denaturation during spray drying.

Similarly the levels of hydroxyproline amino acid residues were increased in wines fined with gelatin and isinglass. It is considered that the level of residual gelatin, as represented by increased hydroxyproline, concentration is a function of this agent’s ability to form soluble complexes with phenolics and polysaccharides. It is suggested that this may act to decrease perceived astringency and bitterness. The small increase in hydroxyproline concentrations seen in wines fined with isinglass is considered to be due to the presence of small quantities of gelatin molecules in the isinglass preparation.