Why Blending in Winemaking Matters

“Blending is the winemakers’ equivalent to chefs cooking up a signature dish,” says Brian Bicknell, owner of the New Zealand winery Mahi. While some wines — such as Burgundies — are made from a single kind of grape grown in a single year, most wines are blends of grapes grown in various years. Blending together wines made from different grapes allows winemakers to combine less-stellar batches — too acidic or tannic, say — to create a wine that’s better balanced.

Every year, Mr. Bicknell sits down with four or five people from his vineyard — including his wife, who he says has a “fresher and more commercial palate” — to make the blending decisions. They spend two weeks tasting and rating 30 or so unbottled wines in stock at the winery, aiming to craft from them an ideal blend, which is then bottled and sold.

As an exercise, you can try blending at home. Start with a few bottles of different mid-to-low-end drinking wines, and keep three rules in mind: Taste your wines at room temperature, not chilled, so the flavors blossom fully; taste the dry wines before the sweet ones; younger before old and more-acidic wines first; and take breaks to prevent “palate fatigue.”

“At the end of the day, the best blend is in the eye of the beholder,” says Mr. Bicknell. “Everyone has a signature style.”

Winemakers usually consider the following before they blend:

Grape type. Different grapes have innate flavors: Sauvignon Blancs, for example, tend to be floral and fragrant, while Chardonnays have a fuller body. And thin-skinned Pinot Noirs grapes are much lighter in tannin than thick-skinned Cabernet Sauvignons grapes.

Vintage. Temperatures yield different flavors in grapes: Colder years tend to result in higher-acid grapes and warmer years in grapes with riper fruit flavors.

Vineyard. Besides temperature, certain vineyards also have specific soil characteristics that filter directly into the taste of the grapes. And certain wine-growing regions favor certain winemaking styles — California winemakers, for instance, prefer different tastes than French winemakers.

Machine or hand-picked. Grapes picked en masse by machines are usually harvested later in the year. Having spent more time on the vine, they produce wines that Mr. Bicknell calls “fruit bombs” because they’ve had more time to ripen and produce sugar. Hand-picked grapes, plucked at an earlier stage of ripening, tend to exhibit less in-your-face fruit flavors, and create wines that carry earthy expressions on the palate.

Pressed vs. free-run. When grapes are machine-pressed, much of the potassium from the skin also seeps into the liquid. This lowers the acidity of the grape juice and adds a “soapy” texture.