Rice hulls for lautering high-wheat mashes

Husk is what makes a lauter tun work

A lauter tun is a filter. The filter medium is the grain itself. Barley husks interlock into an open bed that wort can drain through. Wheat malt has no husk. Neither do rye or oats once they are rolled or flaked. They also carry more protein and gums, especially beta-glucans in rye and oats, which raise wort viscosity.

So a mash with 50 to 70% wheat has two problems at once: less structure and thicker liquid. The bed compacts, the differential pressure across it climbs and runoff slows from a steady flow to a trickle. In the worst case you get a set mash and a long, unhappy afternoon with a rake.

Rice hulls add structure without flavour

Rice hulls are the husks removed when paddy is milled into white rice. They are mostly cellulose, lignin and silica. They carry no starch or enzymes, so they add no extract. Rinsed, they add no flavour either. In the mash they behave like extra barley husk, propping the bed open.

They are not the only option. Oat hulls work too. Some breweries run a mash filter instead of a lauter tun, as our guide to mash filters versus lauter tuns explains. For most craft brewhouses rice hulls are the simplest fix.

Dose 2 to 5% of grist weight, more for extreme mashes

A common range is 2 to 5% of the total grist weight. Where you sit depends on how much huskless grain is in the bill:

• Up to 40% wheat: often none, or around 2%.
• 50 to 60% wheat, as in a Hefeweizen: around 3 to 5%.
• 70% wheat or above, or heavy rye and oats: 5 to 10%.

On a 1,000 litre Hefeweizen with 220 kg of grist at 60% wheat, that means roughly 7 to 11 kg of hulls. Start at the higher end on a new recipe. Once you know how the bed behaves, trim the dose batch by batch.

Rinse them first or taste them later

Dry rice hulls are dusty and can carry a papery, astringent note. Put them in a mesh bag or a clean vessel and rinse with hot water, ideally around 75 to 80 °C, then drain. Rinsing removes dust and any loose surface flavours. It also pre-wets the hulls so they do not soak up wort from the mash.

Add them at mash-in, mixed evenly through the grist. Hulls dumped on top of the mash do very little, because the bed problems start at the bottom near the false bottom. If your brewhouse has a grist case, add the hulls to it so they enter the mash with the malt.

Hulls cost you tun space and a little yield

Rice hulls are bulky. At 5% by weight they can take up noticeably more volume, so check your mash tun headroom before you scale up. They also hold some wort in the spent grain, which trims your brewhouse yield slightly. Most brewers accept that loss happily, because a set mash costs far more in time, oxidation and extract left behind.

Hulls also change the spent grain. If you send it to a dairy farmer as cattle feed, a high hull content dilutes its feed value. Tell them, especially on high-wheat brew days.

Indian rice husk is not automatically brewing grade

India mills enormous quantities of paddy, so rice husk seems easy to find. Most of it goes to boilers as fuel. Fuel husk is not food grade. It can carry dust, stones, mould, pesticide residue and insect damage. Buy brewing-grade hulls from a supplier who can tell you how they were cleaned and stored. Store them dry and sealed like malt, because damp hulls go mouldy quickly in the monsoon.

Hulls work best with good lauter habits

Rice hulls help, but they cannot rescue poor technique. Keep the runoff gentle at the start, especially in the first ten minutes. Keep the bed flooded with sparge water rather than letting it run dry. Rake slowly and at the right height. Our guide to rake height and run-off speed covers the settings.

A short rest around 45 °C or a glucanase enzyme can also reduce viscosity in rye or oat mashes. Choosing between them means understanding which gums your grist carries and how each enzyme behaves with temperature. That is the part of lautering that turns a recipe into a reliable process. Our guide to wheat malt in brewing covers the grain side.

Trial the dose on your next wheat brew

On your next high-wheat batch, add rinsed hulls at 4% of grist weight and log runoff time and differential pressure through the lauter. Repeat at 3% the time after. Two data points will tell you more than any rule of thumb about where your brewhouse needs to sit.

Common questions

How much rice hull should I add?

Usually 2 to 5% of the grist weight. Use more, up to about 10%, for very high wheat, rye or oat mashes.

Do rice hulls affect flavour?

Rinsed hulls add almost no flavour. Unrinsed hulls can carry dust and a papery note, so rinse them in hot water first.

When do I add rice hulls?

At mash-in, mixed evenly through the grist. Adding them on top of the mash does little because bed problems start at the bottom.

Can I use rice husk from a local mill?

Only if it is food grade. Husk sold as boiler fuel can carry dust, mould and residues. Buy brewing-grade hulls from a traceable supplier.