Joe’s Winemaking Notes: December 2015
Sonoma County does not experience the coldest winters in North America. (I can attest to that fact as a former resident of Detroit Lakes, Minnesota and Fraser, Colorado – two communities that have battled for the title “Icebox of the Nation!”) Despite the rather mild temperatures in our county, there’s great value to dormancy in Vitis vinifera grapevines during December, January, and February. Green grapevine shoots are very sensitive to temps below 32 degrees Fahrenheit, yet in the dormant state, our vines are much hardier during periods of frost.
After harvest of our Pinot Noir and Chardonnay in August and September, deep irrigation and light fertilization gave the vines the nutrients needed to produce and stockpile carbohydrates in the trunk and roots. This will be the energy source the vines use to produce the fresh shoots and clusters next spring. With the early 2015 harvest and healthy condition of our vines, they should have ample resources to start strong in 2016!
One concern we have going into winter is the potential effects of a strong forecasted El Nińo. The likelihood in Northern California is that we will receive a lot of rain with warmer temperatures in January, February, and March. This could be both good and bad for our vineyards.
• Our soils would be fully charged with natural rainfall, allowing us to nearly dry farm our grapes again in 2016.
• Warmer temperatures in spring could mean less risk of frost damage after bud break. But, read on for the possibility of an opposite outcome – It’s never easy being a farmer!
• After the vines have received their winter chill requirement (which is minimal for Vitis vinifera winegrapes), only cold temperature prevents the vines from coming out of dormancy. Warmer temperatures could result in a very early bud break in February. This would put us in a risky scenario where warm rainy weather alternates with cold temperatures under clear skies. There are a lot of nervous nights watching the thermometer in February, March, and April!
• Very wet conditions in February and March would limit our ability to get crews and equipment into the vineyard for pruning. Fortunately our Goldridge soils drain very well, and delays are minimal at our estate vineyard.
• Lots of moisture and high humidity increases the early season mildew pressure on our vines. We’ll have to be extra vigilant to prevent damage to our young shoots and clusters. At Rubin Family Vineyards and Winery, we have a great team in the vineyards, and can anticipate and manage tough conditions!
Malolactic Fermentation: Oenococcus oeni ( ē-nō-kok-uh-s ē-n ē) is the scientific name given to one of the most important microbes used in the production of wine. Second in importance only to Saccharomyces (săk’ə-rō-mī’sēz) yeast, the contributions of this single cell organism make fine wine taste and behave very differently! These tiny rod shaped bacteria are very important to the flavor profile of our wines, with the ability to ferment tart malic acid (imagine a Granny Smith apple) into softer, smoother lactic acid. Depending on bacterial strain and fermentation conditions, we can also promote or limit the amount of diacetyl in the wine, which is very important to the flavor of Chardonnay. When you taste a “buttery” Chardonnay, it’s because these ML bacteria have produced diacetyl, the compound that promotes a buttery character. Red wines also go through malolactic fermentation, but for a different primary reason. After completion of ML fermentation, the resulting wine is less likely to begin fermenting again at a later time, such as in barrel (or in bottle!). This allows us extra protection against spoilage. Consider it a pre-emptive strike against spoilage bacteria!
At this time of the year, most of our Pinot Noirs are finished with ML fermentation (Pinot loves to ferment). Chardonnay, on the other hand, is more finicky about temperature and nutrient conditions and will continue to slowly trudge along for another 1-2 months before reaching completion of its ML fermentation. During that time, we will continue stirring the lees (a settled layer of yeast and insoluble components from the grape juice) in the barrels and monitoring biweekly for progress and taste. Once we reach an ideal texture and flavor, the bacteria’s work will be done! Our wines are inoculated with different strains of Oenococcus oeni that are ideally matched to each wine, whether it is our Estate Green Valley Pinot Noir or our Russian River Valley Chardonnay. And as you might have guessed, our Unoaked Chardonnay does not go through any ML fermentation, to maintain the bright acidity that balances out the ripe fruit flavors.