Q: Do the soils where grapes are grown influence the color, flavor, and aroma of wine?
A: The color, flavor, and aroma compounds in wine include those found in the grape fruit—or berry—as well as others that develop during fermentation and aging of the wine. The important point is that all the sensory compounds found in the berry were synthesized within it. In other words, nothing outside of the grape, including the soil, directly contributes chemical compounds that we can sense in wine.
So what determines the specific mixture of sensory compounds in the berries? It’s largely the variety of wine grape, although the environment during the growing season does influence the proportions and intensity of these compounds. This influence can either be a net negative or net positive for wine grape quality.
That brings us to the soil. Soil, of course, is an element of vineyard environments, and it affects wine grapes indirectly—but profoundly—through its impact on water availability to grapevine roots. Moderate water stress to vines during fruit development enhances grape color, flavor, aroma, and acidity. Therefore, vineyard soils that regularly become depleted of moisture early in fruit development lend themselves to high quality grapes.
Soils also affect wine grape sensory characteristics through their supply of mineral nutrients to grape vines. Both mineral nutrient deficiencies and excesses are concerns in this regard and both have negative consequences. For example, boron deficiency inhibits color development in red grapes. Excess nitrogen, meanwhile, is associated with vegetative aromas (e.g., a “green bean” smell) in wines produced from some varieties.
So, although soils don’t contribute chemical compounds directly to grapes and wines, the careful regulation of moisture and mineral nutrient supplies in vineyard soils over the growing season is one reason why competent vineyard management is essential to the quality of wines.
Answered by Stan Grant, a Certified Professional Soil Scientist with Progressive Viticulture, Turlock, CA
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