Malt in brewing terms primarily applies to Barley, but in general can apply to cereal grains. How it works is this: the kernel of the grain is wet and heated - this fools the plant into germinating. At this point, the plant's kernel only contains starch which is of no use for brewing. As the plant germinates, it naturally converts the starch into sugar (maltose) off which to sustain itself until it has rooted (a bit like how the embryo in an egg grows).
The germinated plant is then quickly milled (the end-product being called 'grist') to crack the husk, and it may also be heated in a kiln to change its characteristics (for example to give it a roasted taste). and is ready to mash - i.e. ready for brewing.
Mashing is the process whereby the sugar is washed out the grist using warm water to give a sticky liquid called wort (rhyming with 'dirt'!) which can be brewed along with hops and yeast to make beer.
It comes in three main forms:
As a rule, it's easiest to start out with LME as it keeps for a long time if the cans are sealed, and is easy to use. It doesn't keep that long once the cans have been opened however. Next easiest after that is DME which allows flexibility, and is stronger pound for pound than LME as it has very low water content. Once the bags are opened, use quickly or it'll get very sticky due to moisture in the air. The trickiest to master but the cheapest and most flexible is grain. You need more equipment to mash grains so it's not for beginners.
- grain (as used by breweries as it is cheap and allows lots of control),
- liquid malt extract / LME (wort concentrated into a treacly solution) which is bought in cans
- dried malt extract / DME (wort that has been quickly sprayed with hot air to turn it into a powder) which is usually bought in airtight packets.
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