How malted barley is made

Maltsters trick barley into thinking it is spring, then roast it just as its enzymes peak.

stations: 5
things upstream: 2
raw sources: 2
step from the ground: 1

The short version

Grain gets soaked until it starts to sprout, because a sprouting seed makes the enzymes that turn starch into sugar. The maltster lets that run for several days, then stops it with hot air before the young plant uses up the starch. Brewers and distillers buy the result, with its enzymes still alive.

Dry and rest the grain

Barley arriving with more than 13% moisture is dried with air up to 50 °C, gently enough to keep the embryo alive. It then sits in silos for around six weeks to get past seed dormancy, with temperature watched for signs of insects.

Goes in
Barley
Steep in water

Water covers the grain and moisture climbs from around 12% to as much as 46%. Modern plants alternate wet stands with air rests for two or three cycles. Tiny white rootlets called chit show that the seeds have woken up.

Goes in
Water
Germinate on a slotted floor

For about four to six days the grain grows while fans blow air up through the bed and big mechanical turners keep it loose. Enzymes build up inside each kernel. Barley's husk stays on and protects the growing shoot from damage.
Kiln the green grain

The sprouted grain, called green malt, goes into a kiln where hot air stops the growth. Temperature sets the type. Keeping to 55 °C leaves the enzymes working, and hotter kilning gives darker colors.
Knock off the rootlets

Soon after leaving the kiln, the dried rootlets, called culms, are removed and sold as animal feed. The clean malt goes to brewers and distillers, who later crack it and warm it in water to set the enzymes loose on the remaining starch.

End of the lineMalted barley Next it goes into vinegar, corn flakes, beer and 6 more.

Worth repeating

Malting barley takes about 7% of its extractable starch and turns it into other carbohydrates before the brewer ever sees it.
Floor maltings, where workers raked the grain by hand, began to be phased out in the 1940s.
Barley is the favorite grain for malting partly because its husk survives threshing and later forms a filter bed in the brewery.