The temperature you hold your mash at decides how fermentable the wort is, and therefore how dry or full the finished beer tastes. This guide lays out the active temperature window for each of the main mash enzymes and tells you which ones are working at any rest temperature you enter.
How it works
Each starch-degrading enzyme has a band where it is most active. The two that matter most for the sugar profile are the amylases:
- Beta-amylase (54–66 Celsius): snips fermentable maltose from chain ends, so a lower rest yields a more fermentable, drier, more attenuated wort.
- Alpha-amylase (66–72 Celsius): cuts chains internally and leaves longer dextrins, so a higher rest yields a fuller, sweeter, less fermentable wort.
Supporting enzymes — beta-glucanase, protease and peptidase, alpha-glucosidase, and phytase — work at lower temperatures and affect lautering, yeast nutrition, and pH. The tool marks each as active or inactive at your chosen temperature and estimates how close you are to its peak.
Tips and example
A single-infusion rest at 65 Celsius sits in the overlap of both amylases and produces a balanced, medium-bodied beer — a safe all-rounder. Drop to 63 Celsius for a crisp, dry pale ale, or climb to 69 Celsius for a fuller stout or sweeter malt-forward style. Step mashes string several of these rests together: a short beta-glucan and protein rest before the main saccharification rest, finished with a mash-out near 77 Celsius to denature the enzymes and fix the sugar profile.
All four main enzymes and their roles
| Enzyme | Typical active range | What it does |
|---|---|---|
| Beta-glucanase | 35–45°C | Breaks down gummy beta-glucans in wheat, rye, and oats; improves lautering |
| Protease/Peptidase | 45–55°C | Degrades proteins to aid clarity and yeast nutrition; rarely needed with modern malt |
| Beta-amylase | 54–66°C | Snips fermentable maltose from chain ends; drives attenuation and dryness |
| Alpha-amylase | 66–72°C | Randomly cleaves starch chains; leaves longer dextrins for body and residual sweetness |
Choosing a rest for the style you are brewing
Single infusion at 62–64°C — highly attenuated, dry, sessionable. Suits: American light lager, dry Irish stout, session IPA. Beta-amylase dominates; alpha-amylase is less active and leaves fewer dextrins for the yeast to chew through.
Single infusion at 65–66°C — balanced attenuation and body, the most versatile choice. Suits: pale ale, amber, most German lagers.
Single infusion at 68–70°C — fuller body, moderate attenuation, lingering sweetness. Suits: oatmeal stout, English bitter, hefeweizen (where some residual wheat character is wanted), sweeter malt-forward styles.
Step mash with a beta-glucan rest (35–42°C, 15 min) then saccharification — used for mashes heavy in oats, rye, or unmalted wheat where beta-glucans would otherwise create a stuck runoff. The low-temperature rest activates beta-glucanase to thin the gummy polysaccharides before the main amylase rest begins.
The mash-out
Raising the mash to 76–78°C for 10 minutes denatures the remaining amylases and locks the wort’s sugar profile in place before sparging begins. Without a mash-out, alpha-amylase continues to act during sparging as the temperature slowly rises, which can unpredictably thin the wort. Direct-fire and HERMS systems that can hold temperature during the sparge usually benefit the most from a deliberate mash-out step.