Fermentation Time & Temperature Calculator

Fermentation Temperature Guide

What do I need to know about Q10 Temperature Coefficient?

The Q10 value describes how much faster a biological reaction runs for each 10°C increase in temperature. For most fermentation: Q10 ≈ 2-3 (reaction rate doubles or triples per 10°C rise). Adjusted time = reference time / Q10^((actual_temp − reference_temp)/10). Example: ale fermentation at 20°C takes 72 hours. At 15°C (5°C cooler), Q10 = 2: adjusted time = 72 / 2^(−5/10) = 72 / 2^(−0.5) = 72 / 0.707 = 101 hours. At 25°C: time = 72 / 2^(5/10) = 72 / 1.414 = 51 hours. This relationship explains why a small temperature change has such a large effect on fermentation speed — it's exponential, not linear.

What's the difference between Ale and Lager Temperature?

Ale yeast (top-fermenting, Saccharomyces cerevisiae): optimal 18-24°C. At lower temperatures: stress and off-flavour production. At higher temperatures: fusel alcohols and esters (fruitiness can be intentional). UK ales typically ferment at 18-20°C. Lager yeast (bottom-fermenting, S. pastorianus): optimal 8-14°C. Extended lagering (conditioning) at near-freezing (0-2°C) for 4-8 weeks. Results in crisp, clean flavour. Cold-side fermentation control requires a temperature-controlled fermentation chamber or a cold spot like a garage or cellar, since standard room temperature is too warm for proper lager conditioning.

What do I need to know about Sourdough Fermentation Control?

Sourdough fermentation involves both wild yeast (CO₂ production, leavening) and lactic acid bacteria (LAB: acetic and lactic acid production). Temperature affects the yeast/LAB balance: warm (26-32°C): faster, more lactic acid, milder sourness. Cool (16-20°C): slower, more acetic acid, more complex sharper flavour. Cold retard (4-8°C): very slow, mostly LAB activity, deep sour complex flavour, extended scheduling flexibility. The inoculation rate (amount of starter) and temperature together determine how quickly the dough ferments, giving bakers two separate variables to adjust the schedule around.

What should I know about Signs of Fermentation Progress?

Beer: visible CO₂ bubbling through airlock. Foam (krausen) forming on top. Hydrometer shows dropping specific gravity (SG). Final gravity (FG) reached when SG stabilises over 2-3 consecutive days. Wine: similar but CO₂ production may be less dramatic in early stages. Sourdough: levain/starter doubles in volume. Alveogram (bubble) pattern shows activity. Bulk ferment complete when dough has increased 50-75% in volume with visible bubbles. Off-fermentation signs: an unusual smell — sharp vinegar or nail-polish notes rather than a pleasant tangy aroma — a grey liquid layer (hooch) darker than usual, or visible mould, which means starting again rather than continuing.