Julien's Journal November 2015 (Volume 40, Number 11) | Page 47

by John B. Donovan John is always up for a glass of wine, especially when shared with friends. While his first choice is usually big reds, he’s been known to enjoy dry crisp whites as well. He is also known to enjoy good craft beer on a fairly regular basis. He is the executive director for the Dubuque Mercy Health Foundation. H ave you wondered how wine – fermented grape juice – can sometimes smell like tobacco or vanilla, and taste like cherry pie or leather? If so, you are experiencing stereoisomers. Now, I am hardly the person to explain chemistry to anyone, but suffice it to say that stereoisomers are different configurations of the same chemical compound. For example, scents common to California Chardonnays are apple and butter. You have all tasted the big, buttery-ness of an oaken Chardonnay. But, the winemaker has not added any butter or even a dash of apple. Except in fruit wines such as strawberry or cherry wine, wine is made solely from grapes. main fruit acids: tartaric, malic, and citric in approximately a 3:2:1 ratio respectively. These components, as in all fruits, provide tartness. Tartaric is predominant in grapes, malic is an apple acid, and citric is citrus acid. The combination of these three acids can create many interesting wine flavors and can mimic other kinds of fruit. Further, many wines go through a second fermentation where microbes convert most or all of the malic acid to lactic acid. Lactic acid is the same component that gives yogurt its tartness, and can add buttery notes to a wine’s flavor. Esters, a compound produced by the reaction between an acid and an alcohol, are the aromatic, fruity compounds in wine, formed during fermentation, malolactic fermentation (MLF), and aging. They can come from the grape, but most are produced by yeast during fermentation and aging. Esters make a wine smell fruity. Esters degrade in whites over time, but can increase in red wines. Young wines are full of esters, especially new whites during the first year after fermentation. Reds, though, are seldom released until after the new wine esters have disappeared. More stable esters are responsible for bringing back the fruity complexity that we refer to as bottle bouquet and is a major reason proper aging improves red wine. Acetic acid, more commonly known as vinegar, is present in all wines to some degree. In these small amounts it provides complexity and finish. Too much, of course, the wine can taste like it should be used to dress a salad. Again, proper storage will alleviate this risk. Pyrazines are compounds that offer notes of grass or bell pepper in Cabernet Sauvignon, Cabernet Franc, Merlot, and Sauvignon Blanc. They come from the fruit itself and often indicate that the grapes were harvested unripe or the crop was not exposed to enough sunlight. The Growing Climate It’s no secret that climate affects every vintage, every year, but it also plays a critical role in the development of the individual grape clusters and their intrinsic flavor profiles. For example, a wine’s taste and mouthfeel will be completely different depending on where it was grown. Take a Cabernet Sauvignon grown in a cooler region and one grown in a warm, sunny setting. What happens to the grapes? In the cooler areas, the Cabernet grapes will often display tart, tight flavors like that of red cherries or currants; however, grapes grown in warmer climates present juicier fruit, like that of plums, strawberries, raspberries, and blackberries as a direct result of ripeness levels and sun exposure. I’ve also written about terroir, or the microclimate of the region in which the grape grows. The prevalent winds, irrigation, and type of soil all influence the development of the grape, its sugars and acids, and of course, flavors. So, let’s explore where the other aromas and tastes originate. The array of flavors you find in wine can be credited to three primary areas: the grape itself, the climate where the grape is grown, and the winemaking process. The Grape Did you know that there are about 5,000 different varieties of grapes, but only about 100 are used in wine production? Each grape comes with its own unique compounds within the skin waiting for fermentation. Within grapes, there are three November 2015  ❖  Julien’s Journal  ❖ 45