Climate change is changing the chemical composition of wine

(ORDO NEWS) — Warming temperatures, forest fires and unpredictable weather disrupt the winemaking process.

Shortly after the September 2020 devastation in California’s Napa Valley, wine chemist Anita Oberholster’s mailbox was filled with hundreds of letters from panic-stricken growers.

They wanted to know if they could harvest grapes without the terrible effects on wine: the disgusting ashtray taste known as smoke. Oberholster at UC Davis could only tell them, “Maybe.”

Industrial labs were inundated with grape samples for testing, with waiting times of up to six weeks. Producers didn’t know if it was worth harvesting. Eight percent of California wine grapes in 2020 are left to rot.

Winemakers are no strangers to the vicissitudes of climate change. Rising temperatures have been a boon for some in cooler regions who enjoy more ripe berries, but devastating for others.

Exhausting heat, forest fires and other climatic disasters have destroyed crops in Europe, North America, Australia and other countries.

And as 2020 has shown, climate change can affect grapes without directly destroying them. Forest fires and rising temperatures can change the taste of a wine whose quality and personality depend on the delicate chemical composition of the grapes and the conditions in which they are grown.

Many growers and winemakers are increasingly concerned that climate change is robbing wines of their characteristic flavors and even ruining the harvest entirely.

“It’s a big concern,” says Karen McNeil, a Napa Valley-based wine expert and author of The Wine Bible. “It’s the heartbeat of wine – it’s tied to its place.”

According to McNeil, the biggest challenge climate change poses to winemaking is unpredictability. Producers used to know what varieties to grow, how to grow them, when to pick the berries, and how to ferment them to make a consistent, quality wine, but today every step is up in the air.

This recognition encourages researchers and winemakers to look for ways to preserve their favorite grape varieties and their unique qualities in the changing and capricious conditions of today’s warming planet.

Extreme weather can kill even the hardiest vines, but most of the climate threat is invisible: chemical changes in the berries.

This is because the quality of wine, in its most detailed form, comes down to achieving a balance between the three broad aspects of berries: sugar, acid, and secondary compounds.

The sugar builds up in the berries as the grapes photosynthesize, and the acid breaks down as the grapes ripen.

Secondary compounds – mostly chemicals other than those needed for the plant’s basic metabolism – build up over the course of the season. Substances called anthocyanins give red grapes their color and protect the plant from UV rays.

Other substances called tannins give wine its bitterness and astringent, drying taste in the mouth. For vines, they provide protection from grazing animals and other pests.


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