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How Temperature Affects Grapes in Winemaking

Grapes of the same variety will give very different wines, depending on the climate in which they’re grown. Why does that happen? What does temperature do to the grapes?

THE WINEMAKING PROCESS

When wine is made, it follows a similar process each time. The grapes grow on the vines, then are picked, pressed, squeezed, and macerated – with or without their skins. The liquid ferments, and afterwards is aged and bottled.

During the fermentation process, the sugar in the pulp is converted into alcohol, turning it into wine. So where does the temperature difference come into play?

THE SWEETNESS OF WARMER CLIMATES

Grapes that grow in warmer climates mature differently from grapes that have grown in cooler places. All grapes start out the same, as small, hard, green fruits with high levels of mostly malic acids, and very little sweetness. When grapes grow somewhere hot, they ripen faster and turn out sweeter – the original acidity levels in the pulp of the grape fall, as the sugar content rises.

This means that when they’re fermenting, they have more sugar to convert into alcohol, resulting in stronger wines with ripe, sweet flavours.

In cooler climates, the grapes ripen more slowly. These climates lend themselves well to green grapes, which retain a certain level of acidity. Wines from cooler climates tend to be more acid and less sweet, with dry, fresh flavours, and a lower level of alcohol.

COOL CLIMATE GRAPE VARIETIES

Cooler climates are famous for their white grapes, such as Sauvignon Blanc, Chardonnay, Riesling, and Bacchus. These tend to have light bodies and citrusy flavour profiles, with low alcohol content and high acidity.

Some varieties of red grape also thrive in cooler climates, like Pinot Noir, Merlot, Gamay, and Cabernet Franc. They also tend towards lower alcohol content and high acidity, with spicy flavours and light bodies.

WARM CLIMATE GRAPE VARIETIES

Whilst white grapes aren’t always associated with hot climates, some varieties can handle the heat. These include Muscat, Chenin Blanc, and Blanc du Bois – and grapes like Sauvignon Blanc can also grow in warmer climates, producing very different flavours when cultivated in this way. They produce sweeter wines with slightly tropical profiles.

When red grapes grow in warmer climates, their skins thicken to protect themselves from the heat. Grape skins add tannin to wines, meaning that red wines from warmer regions are generally tannic and higher in alcohol, with rich, sweet flavour profiles. Some varieties that love the warmth are Zinfandel, Cabernet Sauvignon, Grenache, and Shiraz.