What is the relationship between fruit color and wine color concentration?
A strong, positive relationship exists between anthocyanin (i.e. color) concentration in grape and in wine (source). However, all anthocyanins accumulated in the skin are not completely extracted into the wine. For that reason, even if a relationship exists, the total amount of anthocyanins extracted from berry skin is always higher than the total amount of anthocyanins found in the wine. In practice, how can a winemaker leverage this relationship to improve harvest decision?
The rate of color accumulation throughout ripening can predict wine color
If you monitor the time profile of berry color concentration, you can measure the rate at which color accumulates. Then if you compare the rate of berry color accumulation with wine color, a very interesting correlation appears (Figure 1) In fact, research has shown that the rate at which anthocyanins accumulate correlates to wine color density. Figure 1 shows that the faster color accumulates during ripening, the higher is wine color density at bottling. Interestingly, Figure 1 also shows that the effect between faster rate of anthocyanin accumulation and higher wine color persisted 10 months after bottling. Knowing the rate of color accumulation before harvest is a useful information to estimate the potential wine color density.
Figure 1: Association between rate of accumulation of anthocyanin in berries and wine color density at bottling and 10 months after bottling.(from Sadras et al, 2007)
The significant correlation between rate of anthocyanin accumulation and wine color density reinforces the notion that tracking the rate at which anthocyanins accumulate is relevant to assess fruit composition effect into wine properties. But why would color affect wine properties beyond color?
Color monitoring is not just for color!
Anthocyanins play a direct role in the rate of tanins extraction from the fruit into the wine (here). For that reason, when color accumulation is slow, delaying harvest can be a good practice to increase total wine tannin as reported by Bindon and her team.
Wine color contributes to wine sensory properties and consumer preference.
A 2017 study lead for 2 consecutive vintages with Cabernet sauvignon investigated the ability to predict wine style from tasting grapes. The goal was to improve our understanding of the relationship between berry sensory assessment and wine sensory attributes. By comparing the sensory properties of Cabernet Sauvignon grapes and the corresponding wines, authors found that anthocyanin were reliable contributors to wine sensory attributes.
Thus, knowing the rate of color accumulation is a relevant information for a winemaker before harvest. It helps positioning the picking decision according to:
- The speed of color accumulation
- The trend (up or down or steady) of color accumulation profile just before harvest day. This gives an early insight in wine color density and tannins concentration which directly drive consumer preferences.
Practical take home:
Monitoring berry sugars and color time profiles inform on many other biochemical processes. Those processes ultimately are affecting wine chemical composition and sensorial properties. We discussed over this blog and the previous one that:
- Monitoring dynamics of sugar per berry is more informative than monitoring sugar concentration.
- Sugar is a signal for secondary metabolism changes such as color accumulation.
- The rate of berry sugar accumulation can be used as a proxy for anthocyanins accumulation.
- Anthocyanins contribute to wines sensorial properties.
- If you track simultaneously sugar accumulation and anthocyanins accumulation water deficit will increase the rate of color accumulation in relation to sugars accumulation.
- By analyzing berry ripening dynamics, you can be more consistent in your harvest decisions, and adapt your practices to the effects of higher temperatures.