A closer look at grape development can be understood during the process of "Veraison" .
This year, 2020, will not be forgotten any time soon. Our human world is changed, for many, not so good, others very good, but for the vines, outstanding! I have intimate memories of each vintage and what the wines became but I will never forget this vintage because the environment and the vines are thriving like never before. I have seen many great vintages where our weather was picture perfect and we avoided spring and fall frost, insect infestations, and heat waves. But 2020 is like no other and though it would be great for everyone to be able to “get back to normal”, as a farmer and vintner, I am hoping for more vintages like this. More vintages of peaceful, blue skies void of airplanes and the pollution and noise that come with our very fast-paced society.
It is mid-August and the berries have started the process of veraison which is the onset of ripening. “Veraison” is a French term meaning simply change of color of the grape berries. Veraison is the transformation from berry growth to berry ripening and many changes in berry development take place.
Wine grape berries start out green and it is presumed they change color because the chlorophyll, which is green, is broken down. What triggers veraison is still unknown, but in white wine grapes, carotenoids are formed, you know, the pigment that gives carrots their orange color or pumpkins their orange color, and the yellow color in corn. Carotenoids also give Salmon, flamingos, canaries, lobster, shrimp and daffodils their color. White wine grape skins typically do not turn red or purple in color for this reason.
In red wine grapes, anthocyanins and xanthophylls are formed. Depending on pH, anthocyanins, (water soluble enclosed pigments), can appear light red to dark purple and blue like found in red cabbage, fall leaf colors, blueberries, raspberries or black rice.
Xanthophylls produce yellow to red pigment like carotenoids, but contain oxygen, (whereas carotenoids contain only hydrogen) and are responsible for leaves turning yellow and the yellow color of yolk in chicken eggs. Xanthophylls are also found in papaya, peaches, prunes, squash, spinach, parsley and pistachios!
Now you know more than you ever wanted to know right? NOT! Let’s appeal to the mathematicians now as we talk further about berry development. The berries have gone through growth phase one and are now transforming (veraison) into phase 2, development also called ripening. Grape berries follow a double sigma growth curve. Simply put, a double sigma growth curve means an “S” shaped curve. What this means is as the berry matures the initial growth phase is a result of cell division and cell expansion. (The bottom of the “S” to the middle). Then there is a “lag” phase which is when veraison occurs. (The middle part of the “S”). In the second growth phase into full ripening, (top of the “S” downward) the acidity of the berry decreases while at the same time the sugar content, fructose and glucose, increases reducing the volume of water in the berries causing them to slightly shrink or no longer grow larger.
In a nutshell, (too late for that!) the annual growth cycle of a grapevine begins with bud break after pruning in the spring and culminates with harvest. In general, the number of days it takes for berry development from bud break to veraison, is the same number of days it takes from veraison to harvest or a balanced, fully ripe berry ready to be made into my favorite adult beverage. So there you have it. Bud break occurred in our vineyards around May 1 and we are in veraison now, August 12, so exactly when will you all show up for harvest?
Karen J Wood