In our northern latitudes, things change from year to year and what you got last year may not be what you get this year. There are a few tricks to getting a heads up to minimize surprises on the crush pad.
First of all, get to know the vineyard where you source your grapes. What is the soil profile like? Does it have good enough drainage that growth can be controlled by appropriate watering. Is the vine spacing wide enough to allow balanced growth without multiple hedgings and toppings throughout the summer? Is the air drainage good enough that the season won’t end prematurely with an early frost? One last and very difficult question: Is the season length of the grape variety matched to the frost free growing days and the typical growing degree days of the site? This is the foundation of a vineyard that will give you more consistent composition in spite of changes in heat units and rainfall from year to year.
There are two potential problems if the grape variety doesn’t match the vineyard. If the grape is a long season variety such as Riesling or one of the Cabernets on a cooler site, then you may have to cope with immature grapes in all but exceptional years. Watch for cane darkening, taste the berries, chew up the seeds and skin to assess ripeness. Don’t depend on lab tests alone to tell you when to pick. You could end up having to cope with green flavours, pale colour, and thin body. The quick fix for a red wine is to not make a red wine. Make a rosé or blush, or if the problem is really severe, make a sparkler.
If you have no choice except to make a red, you can press out part of the batch, make a blush with that and return the pomace to the skin extraction part of the fermentation. If your TA is so high that it can’t be corrected by a malolactic or the usual tartrate precipitation, you can do a double salt precipitation or potassium bicarbonate correction on part of the blush you extracted and add that back to your main batch. At maturity the malic and tartaric acid of grapes is typically about 50:50 so a malolactic fermentation will drop the TA by about 25%. Cold stabilization may drop TA by about two g/L. Vegetal flavours tend to be broken down by oxidation, so a délestage fermentation can assist you to unmask the fruity notes and minimize vegetal notes. You may also need to take steps to augment the palate. Oak chip press aid during skin fermentation can assist this. You may also wish to add skin tannin to balance the astringency. The more adjustments that you can make early in wine development, the better will be the final palate. There is little to be gained by extended skin contact of immature grapes, so press them and move into an early malolactic followed by a sûr lie autolysis.
There is also the possibility that grapes could mature early and have less than normal varietal character. When the last thirty days of the season are above 20°C average, the rate of loss of volatile flavour compounds may be greater than their rate of synthesis, resulting in a wine with nondescript varietal character. Add to this the grapes be overmature at harvest and the wines may lack acidity, have high pH, and high alcohol. The easiest factor to deal with is pH. There are several options. If tartaric acid is added, the pH will drop by approximately 0.2 pH units per gram of tartaric acid. Initially the TA will rise by the same amount as the added acid, but the tartaric acid will eventually precipitate as potassium bitartrate, thus removing potassium ion and leaving the pH at the lower level. Citric acid or malic acid have approximately the same effect, but they are more soluble and will not precipitate. Thus the TA will remain at the adjusted level. Use care with citric or tartaric acid to ensure that no malolactic fermentation is initiated.
To develop more intense varietal character, the extraction from skins must be enhanced. This can be accomplished either by extended skin contact or by the use of pectinase to break down the berry structure, either in whites or reds. In white wines this must be done with caution in order to assure that excess tannins aren’t extracted. The wine may require fining to remove excess astringency, depending on wine style.
The bottom line is that a fundamentally good growing site should be versatile enough to give good performance in good or bad growing seasons. With a little care, good wines can still be made in spite of an adverse season.
This article was first published in British Columbia Fruit Grower