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Mashing: the temperature rests that decide strength and body

Which enzyme works at which temperature, why 63°C gives a dry beer and 70°C a fuller one — with real Castle Malting mash schedules for lager, wheat beer and stout.

26 Sept 2026 · 8 min read

Mashing is steeping crushed malt in hot water so the malt's own enzymes cut starch into sugar. The temperature you hold decides which sugars are made — and so whether the beer ends up dry or full, strong or light, with lasting or fleeting foam.

What happens in the mash

Barley malt starch gelatinises (absorbs water, swells and bursts) at around 60–65°C. Once gelatinised, two main enzymes go to work:

β-amylase (most active at 60–65°C): trims from the chain ends, making maltose — sugar yeast fully ferments. Result: a dry, lighter-bodied, stronger beer. It denatures quickly above 65°C.
α-amylase (most active at 68–72°C): cuts randomly inside the chain, making dextrins — sugars yeast can't ferment. Result: a sweeter, fuller beer with better foam.

The mash rests at a glance

Temperature	Rest	Main enzyme	Purpose
35–45°C	β-glucan rest	β-glucanase	Giảm độ nhớt, tránh tắc lọc (nhiều yến mạch, lúa mạch đen) · Lower viscosity, avoid stuck sparges
45–55°C	Protein rest	Protease, peptidase	Tạo dinh dưỡng đạm (FAN) cho men · Free amino nitrogen for yeast
60–65°C	β-amylase (saccharification)	β-amylase	Tối đa đường lên men → bia khô, cồn cao · Max fermentable sugar
68–72°C	α-amylase (dextrinisation)	α-amylase	Dextrin → thân dày, ngọt đằm, bọt bền · Body, sweetness, foam
76–78°C	Mash-out	—	Dừng enzyme, dịch loãng hơn để lọc nhanh · Stop enzymes, thinner wort for lautering

Modern malts (Pilsner, Pale Ale) are well modified, so keep any 45–55°C protein rest very short (≤ 10 minutes) or skip it. A long protein rest thins the body and hurts foam.

Real mash schedules from Castle Malting (Belgium)

Castle Malting's 100 L sample recipes all use mash pH 5.3, 2.8–3.0 L of water per kg of malt, 1°C/min ramps between rests and an iodine test before mash-out:

Style	Mash schedule	Result
American Lager (75% Pilsen, 20% bắp mảnh · maize flakes)	52°C 5′ → 63°C 40′ → 72°C 15′ → 78°C 2′	11,5°P → 2,2°P · lên men 81% · 5% ABV
Wheat beer kiểu Hoegaarden (70% Pilsen, 30% lúa mì · wheat)	63°C 50′ → 72°C 20′ → 78°C 2′	11,5°P → 2,25°P · 80% · 4,9% ABV
Imperial Stout (60% Pilsen + Abbey, Chocolat, Cara Ruby, lúa mạch rang)	62°C 45′ → 72°C 20′ → 78°C 2′	15°P → 3,4°P · 77% · 6,5% ABV

Notice: beers meant to be dry and easy-drinking (lager, wheat) spend longest at 63°C; the stout, which needs body, rests longer at 72°C. For a single-infusion mash, 65–66°C is the balance point; 63–64°C for dry, 68–69°C for full.

Iodine test before mash-out

Put a few drops of liquid (no husks) on a white plate.
Add one drop of iodine solution.
Yellow-brown: conversion complete, go to mash-out. Blue-black: starch remains, rest 10–15 minutes more and retest.

An all-in-one brewer with a controller and recirculation pump holds each rest to ±0.5°C and runs multi-step schedules automatically — hard to do on a gas stove.