Malting is the process in which raw barley or another grain is made ready to become the main ingredient in the brewing process. The grain is steeped in water, then rested under precise conditions to encourage germination, and finally dried in a kiln and/or a roaster. See malt. Professionally, the person responsible for this process is known as a maltster. Malting is essentially the first step in beer making; the second is mashing, lautering, and boiling in the brewhouse; the third step is fermentation in the cellar; and the final step is the packaging of the beer in kegs, bottles, or cans.
One of the key functions of malting is to degrade the grain’s proteins and to create the enzymes and modify the starches needed for the brewing process. See modification. The time and temperatures for each malting step vary from one maltster to the next and from one type of malt to another. The first step of malting is steeping the raw grain in a vat of clean and fresh water. During steeping, which may take up to 2 days, the grain is alternately soaked and then drained in intervals of about 8 h. During this time, the barley corn absorbs water, which, in turn, activates enzymes that reside naturally in the grain and are capable of breaking down complex molecules within the kernel, notably proteins and carbohydrates. It also activates hormones responsible for starting the growth of a new plant. Whereas the moisture content in siloed raw grain rarely exceeds 15% by weight, after the steep it is about 45%.
At this point, tiny roots known as “chits” become visible, and the damp grain is transferred to a germination room, which is usually kept between 16°C and 19°C (61°F and 66°F). There, the germinating barley is well aerated for 4 to 6 days and turned frequently. The turning of the barley keeps the rapidly growing roots from matting together; it also dissipates moisture, heat, and carbon dioxide produced during the grain’s respiration. See respiration. Today, the turning of grain is usually done my mechanical means, but it is a task that has also been done by hand for thousands of years. See floor malting and saladin box.
During germination, the grain enzymes kick their activities into high gear, producing malt sugars, soluble starch, and usable yeast nutrients such as amino acids. See starch, sugar, and yeast nutrients.
Now the grain is ready to be fully dried. For this it is moved into a kiln. See kilning. The heat of the kiln, which is usually 80°C to 90°C (176°F–194°F) and lasts for approximately 2 to 4 h, kills the embryo of the sprouting grain and preserves its nutrients for beer making rather than for making a new plant. The enzymatic modifications that started in the steeping vessel and continued during germination also continue during the initial heating of the grain. As the grain dries out and becomes malt, the enzymes become dormant and modification stops. Later, in the brewhouse, these enzymes will be reactivated by heat and moisture in a mashing vessel. At the end of the process, the finished malt has 3%–6% moisture and can be stored for months.
For specialty malts such as caramel or crystal malts, the process is similar to that for base malts, with some alterations to give specialty malts their variations of color and flavor. Caramel or crystal malts are essentially stewed until their starches liquidize into sugars and then roasted to caramelize those sugars. Roasting done with little moisture does not result in caramelization but develops color and roasted flavors. See maillard reaction and melanoidins. Higher drying temperatures will result in darker, more flavorful malts, but the malt’s enzymes may become permanently denatured. Such malts have no enzymatic power and cannot be used as base malts. See base malt. The flavors of specialty malts may range from toffeelike, to nutty, to coffeelike, to sharp and almost burned tasting. Malt colors may range from golden yellow to pitch black. See caramel malts and roasted malts.
Characteristics of malts will differ partly depending on whether the raw grain used was two-row or six-row barley. Six-row barley malt tends to have more polyphenols and more enzymes than does two-row barley malt. This is principally because the kernels of six-row barley are generally smaller than those of two-row barley, giving six-row kernels a greater husk-to-endosperm ratio. See endosperm and husk. Six-row malt, however, tends to work well with raw adjunct grains, because its higher enzymatic power is capable of converting their starches. See adjuncts and diastatic power.