Winemaking Info

wmfreetrial

John Overholt attended the Washington Association of Wine Grape Growers convention, from which he is sharing the following information:


In reviewing some of the presentation material from the WAWGG Convention, I was struck by how my experience at Artz corroborated some information presented by Jim Harbertson (WSU) and several others.

The research they did was on the Impact of Cabernet Sauvignon and Syrah Berry Maturity and Alcohol Content on Anthocyanin, Tannin, and Polymeric Pigment Content Over Time.

Objective: determine the most important factor to maximize polymeric pigment formation in wines

· Monomeric anthocyanins are responsible for color in fruit and young wines
· Once extracted into wine, anthocyanins are relatively unstable
· Anthocyanins react with tannins (responsible for astringency) to form polymeric pigments
· Polymeric pigments provide wine:
o Stable color
o A decrease/modification in astringency
· Berry maturity increases berry color (until late season oxidation/degradation)
· Higher wine alcohol increases tannin concentration
· Experiment was designed to vary initial anthocyanin and tannin content as well as the ratio between the two

Conclusion:

· Initial wine (not necessarily fruit) anthocyanin concentration is the best single predictor for long-term polymeric pigment formation.
· Higher initial anthocyanin content leads to more stable color and astringency modification over time.
· Overripe fruit had highest levels of polymeric pigment for Syrah while ripe and overripe fruit had highest levels in Cabernet Sauvignon.
· Polymeric pigment formation occurs relatively rapidly in wines.
· Reaches a maximum after approximately 1 year at cellar conditions.

I usually source wines from a number of vineyards, and I’ve been struck by the level of anthocyanin concentration in the Artz fruit. I see it in the cab and merlot especially, but particularly the Syrah. From an enological point of view, the instability of anthocyanins also points to the value of adding tannin (cubes, fermentation tannins, etc.) and early on in the fermentation. Anthocyanins react with tannins (and I believe oxygen) to form polymeric pigments that are responsible for the level and nature of astringency (harsh vs. softer) you get from the wine.