Malting serves the purpose of converting insoluble starch to soluble starch, reducing complex proteins, generating nutrients for yeast development, and the development of enzymes. The three main steps of the malting process are steeping, germination, and kilning.
The purpose of steeping is to evenly hydrate the endosperm mass and to allow uniform growth during germination. Steeping begins by mixing the barley kernels with water to raise the moisture level and activate the metabolic processes of the dormant kernel. The water is drained, and the moist grains are turned several times during steeping to increase oxygen uptake by the respiring barley. A wide variety of steeping regimes are used, depending on the steep vessel configuration, barley variety, barley quality, kernel size, brewery specifications, and maltster preferences (21).
In the next step, the wet barley is germinated by maintaining it at a suitable temperature and humidity level until adequate modification has been achieved. The techniques most commonly used for germinating barley are floor malting and pneumatic malting. Floor malting is an old process in which the chitted malt is spread on the floor to a height of 10 to 20 cm. Pneumatic malting uses forced air for the germination process. There are numerous mechanical designs for pneumatic malting such as drum malting, compartment malting, continuous malting, and tower and circular malting, and flexi malting.
The final step is to dry the green malt in the kiln, which is done at different temperatures. The temperature regime in the kiln determines the color of the malt and the number of enzymes which survive for use in the mashing process. For example, low temperature kilning is more appropriate for malts when it is essential to preserve enzymatic (diastatic) power. These malts are high in extract but low in coloring and flavoring compounds. Pilsner and pale ale malts are examples of malts kilned at low temperatures. Malts kilned at intermediate temperatures, such as Munich and Vienna malts, are lower in enzymes but higher in coloring and flavoring compounds. Malts kilned at high temperatures, such as crystal and chocolate malts, have little if any enzymes thus are lower in extract.
Click on the following topics for more information on barley malts.