Mashing — controlling sugar profile and body

What’s happening in the mash

When milled malt meets hot water, the malt’s enzymes activate. Different enzymes work at different temperatures and produce different sugars:

Why temperature determines body

If you mash low (65 °C and below), β-amylase dominates: you get a high proportion of maltose, which the yeast can ferment almost completely. Result: dry, thinner beer.

If you mash high (68 °C and above), α-amylase dominates: you get longer, more complex sugars that yeast can only partially ferment. Result: fuller, sweeter beer.

Practical: mash a hop-forward IPA at 64-65 °C for a drier finish. Mash a milk stout at 68 °C for body. Most everyday ales work at 66-67 °C.

Single-infusion vs step-mash

Modern malts are so well modified that single-infusion at 65-67 °C works for nearly everything. You only need step-mashing for:

• Older or undermodified Continental malts (rare today)
• Wheat-heavy beers where a protein rest helps head retention
• Strict traditional decoction-mash Continental lagers, for flavour rather than necessity

A 60-minute single rest hits full conversion for any modern base malt. You can verify with an iodine test (drop wort onto a white tile; if it turns blue, starch remains).

Sparging

After the mash, you rinse the sweet wort out of the grain bed:

• Fly sparging — slow, even sprinkle. Highest efficiency.
• Batch sparging — flood with sparge water, stir, drain. Slightly lower efficiency, much simpler.
• No-sparge (BIAB) — single full-volume mash, lift bag, done. Lower efficiency, fastest brew day.

All three approaches make excellent beer. Pick one based on equipment.