| VIN-SIGHTS |

BY MARNIE OLD

All the world ’ s finest vineyards have something in common : Whether they are in a warm or cool climate region , they almost always feature an unusually big drop in temperature from the daytime high to the nighttime low . Known as a large “ diurnal swing ,” this is a consistent feature of the finest terroirs .

Sun is essential for making great wine , of course . Fruit needs ample sunshine and warmth by day to ripen , providing the energy necessary to produce sugar , flavor and color in the grapes . But if ripening proceeds too fast , the grapes will lose the acidity that provides wine ’ s refreshment and food-friendliness . If vines get too much heat too quickly , grape flavors will shift from bright and fresh to cooked and jammy in a flash .

Cold nights act almost like a refrigerator , preserving fruit freshness whether the coolness comes from ocean breezes or clear desert skies . These boost wine quality by postponing the drop in grape acidity and retaining the desirable aromatics associated with early stages of ripeness .

Marnie Old is one of the country ’ s leading wine educators . Formerly the director of wine studies for Manhattan ’ s French Culinary Institute , she is best known for her visually engaging books published by DK , including Wine : A Tasting Course . Marnie currently serves as the director of vinlightenment for Boisset Collection .

1 ) HERE COMES THE SUN Sunlight fuels fruit ripening through photosynthesis .

This process is sensitive to temperature : the warmer a vineyard gets , the faster grapes ripen .

4 ) REFRESHMENT BY NIGHT : PRESERVE ACIDITY AND ADD COMPLEXITY Overnight temperature drops help grapes retain necessary acidity , but also help develop more “ complexity ” in the wine ’ s aromas and flavors .

2 ) ENRICHMENT BY DAY : DEVELOP POWER ,

FLAVOR AND TEXTURE As grapes ripen , they produce compounds that deepen color and intensify flavor .

Grape sugar , or potential alcohol , increases rapidly , which adds body to wine . Acidity decreases , which is essential for fresh flavors , foodfriendliness and balance .

3 ) GOOD NIGHT , MOON The lower the temperatures drop after sunset , the slower the ripening process will proceed .

WINEMAKERS WANT A BIG DIURNAL SWING TO SLOW RIPENING

Wine regions that are sunny and warm by day but cool off dramatically at night typically make the highest quality wines . For example , California ’ s coastal fine wine regions , from Napa Valley to Santa Barbara County , all feature a dramatic variation in daily temperature from day to night , as ocean breezes cool the vineyards come evening . The nearby vineyards of the Central Valley may be quite productive in volume terms , but their wines have much lower quality potential since the grapes do not cool off as much after the sun goes down .

12 | SPRING 2021 • CHEERS @ HOME