CO-PIGMENTATION

"CO-PIGMENTATION". functionally speaking,

relates to how stable the color will be in your red wines.

Color extraction is complete in about 4 days. Color is water soluble. It does not increase with more time or temperature, nor alcohol content.

Since color is water soluble, full color can be achieved during a cold maceration soak prior to alcohol fermentation.

Color is dependent on solubility which is basically pre-determined relative to the grape cultivar, microclimate, year you are processing.

However, color stability depends on co-pigmentation.

Color pigments (anthocyanins) make "stacks" which then link with the tannins (phenols) and other "co-factors". This is co-pigmentation. If color pigments linked with tannins are the "wall", co-factors are the "cement" that keeps the wall stable.

For example, Pinot Noir lacks enough phenols to link with the anthocyanins, often resulting in  unstable color.

Traditionally, some white grape skins (not juice) have been added to some red grape fermentations to provide these co-factors.

The amount of available tannins (phenols) increases with skin time but levels off by about 5* Brix.

Extended masceration increases tannins from the contribution of seed tannins.

Stable Color = "Condensation" and "Co-pigmentation"

Color Loss = Oxydation of monomeric color pigments. These are color pigments that have not condensed with polymeric phenols. Monomeric color pigments are susceptible to oxidation by oxygen and sulfite ions.

Final Color = rate of condensation versus the rate of oxidation.

Timing of Finings: Protein fining agents (gelatin, casein, isinglas, egg whites) remove polymeric phenols/tannins.

50-70% of color pigments are in the polymeric form by 4 months.

The higher the pH, the slower the polymerization, the more unstable the color.

Therefore, fine early (as soon as basically clear, 1-3 months after ferment) to remove harshness while there is an excess of polymeric tannins. Later fining removes polymeric phenols that have the color pigments in a stable, condensed and co-pigmented form = unstable color.

Gelatin is the most aggressive, non-specific, and effective tannin remover…and, should only be used early in those 1-3 months after fermentation to remove excessive skin and barrel tannins.

Casein, egg whites, isinglas are more gentle, removing less tannins and gently improving mouthfeel by reducing astringency.

They are used after using gelatin and may be safe to use later on, 1-2 months prior to bottling.

Re-cap:

• Color stability depends on co-pigmentation.

• Co-pigmentation is a linking of the color pigments and polymeric tannins and co-factors.

• Tannins polymerize (link-up) with time. 70% complete by 4 months.

• Color pigments not linked to polymeric tannins are unstable.