The variable winemakers watch most closely
Of all the decisions made during fermentation, none is monitored as closely as temperature. It's not a minor technical detail: it determines how fast the yeast works, how much color and tannin get extracted from the skins, and whether the wine's fruity aromas survive the process or get lost along the way.
Whites: cool, between 12°C and 18°C
White wines ferment at low temperatures on purpose. Heat destroys the volatile aromatic compounds that give wine its fruity and floral notes — fermenting cool is, in large part, a strategy to keep those aromas intact all the way to the glass. The trade-off is a slower process.
Reds: warmer, between 25°C and 30°C
Red wines ferment together with the grape skins, and heat helps extract the color and tannin that give the wine its structure. Fermenting warmer also speeds up the yeast's work, which is why reds often finish their alcoholic fermentation faster than whites.
What happens if it climbs too high
Above 35°C, the yeast starts to struggle: at that temperature it can die before finishing its job, leaving an incomplete fermentation. Excess heat also produces cooked or raisiny fruit notes instead of fresh fruit, and raises the risk of volatile acidity — a defect that gives the wine a vinegar-like smell.
What happens if it drops too low
Below 10-12°C, the yeast becomes nearly dormant and fermentation slows dramatically or stops altogether. This is what winemakers call a stuck fermentation — a serious problem, because the leftover unfermented sugar is a perfect entry point for unwanted bacteria.
Why temperature control is so critical: a stuck fermentation doesn't just risk the wine's style — it can ruin the entire batch if the wrong bacteria take advantage of the leftover sugar.
How LagarLab simulates this
In the simulator, temperature is an active control on your tank, with real alerts if you drift outside the safe range for the style you're making — the same logic a real winemaker follows, without the risk of losing an actual batch while you experiment.
What if you controlled the temperature, with real data?
In LagarLab you set your tank's fermentation temperature and watch in real time what happens to the wine if you push it out of range.
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Frequently asked questions
What happens if fermentation gets too hot?
Above 35°C, yeasts get stressed and can die, leaving fermentation incomplete, with cooked or raisined fruit notes and a risk of volatile acidity — a defect that smells like vinegar.
What if the temperature is too low?
Below 10°C to 12°C, yeasts nearly stop working, which can lead to a stuck fermentation — a serious risk, because the leftover unfermented sugar can attract unwanted bacteria.
Why do whites ferment cooler than reds?
Cooler temperatures, between 12°C and 18°C, preserve the fruity aromatic compounds in whites, which heat degrades. Reds ferment warmer, between 25°C and 30°C, because that heat helps extract color and tannin from the skins.
How do wineries control fermentation temperature?
Mostly with stainless-steel tanks that have a cooling jacket, where cold water or glycol circulates, or with cooling plates and heat exchangers. Fermentation itself releases heat, so the usual job is to cool, not to warm. The temperature is checked at least once a day, and in reds the pump-overs also help even it out between the cap of skins and the liquid. In LagarLab you set the tank temperature every day of the fermentation and see its effect on the yeast.