Tannin is a key determinant of astringency in wines. Dr. Kennedy’s talk at our 2015 Vintage Report conference in Napa explores how tannin structure interacts with tannin activity in the presence of other factors like climate and management practices. Dr. Kennedy is one of the leading experts in the subject of wine tannin. The talk touches on how tannin develops and key determinants of tannin activity.
It’s important to understand how tannins develop in the fruit. Tannins are formed in the first phase of berry development, while sugar accumulates during the second phase. A key consideration for viticulturists and winemakers is how to balance the chemicals developed during ripening versus berry development. Needless to say, professional winemakers attempt at a large variety of methods to get the right balance.
Tannins are found in the seed, skin and stem of the berry. During the first phase of berry development, tannins are formed and continue to evolve as the berry develops and ripens.
What has to be true in order for tannins to be extractable into wines? The process, in fact, is not straightforward. Phenolics, which reside behind plant cell walls, need to break through vacuolar membranes and plant cell membranes in order for extraction to happen. Furthermore, tannin molecules tend to stick to cell walls. Thus not all tannins formed in the berry are extracted into the wine.
Tannin structure and activity
There are a variety of aspects we can measure to understand tannin, namely tannin concentration, tannin pigmentation and tannins composition. Dr. Kennedy used the term “tannin activity” to represent the net effect of all these factors i.e. how tannins interact with the saliva proteins during wine tasting.
More specifically, he’s interested in:
- The sensorial aspect that wine produces in your mouth
- The duration relative to the magnitude (or maximum amount) of astringency.
As wine enters the mouth, astringency builds up then goes down. As tannin get more sticky, it becomes more active. The duration of astringency increases relatively with maximum amount astringency.
Large tannins, seed tannins, unpigmented tannins, newly extracted tannins tend to induce a sensorial effect characterized by long duration relative to magnitude of astringency.
Thus, depending upon the desired wine profile for a given varietal, winemakers want to modify the tannin structure of the wine to gravitate towards:
- smaller-sized tannins
- tannins originating proportionally more from skin than seed
- more color incorporation (higher proportion of pigmented tannin).
Those features contribute to reduce the perception of duration relative to magnitude of astringency.
Check out the full talk here. In a future post, we’ll talk about recent experiments concerning the effect of tannin structure with respect to tannin activity and wine astringency.
The Vintage Report brings together scientists, winemakers and industry leaders from all over the world to produce a one-day seminar that brings together open minds within the industry to discuss the previous year’s harvest in light of the most recent scientific findings and newly available data. Our biggest impact is asking the question: how can we leverage what we learned this year to improve vineyard practices and wine quality? Check it out at https://www.vintagereport.com.
This post was written by Elise Nguyen and Thibaut Scholasch.