Malting And Kilning Malt Whisky

The barley is cleaned and then steeped in cold water for 2 to 3 days. After soaking, the water is drained off and the grain is spread out to a depth of 2 to 3 feet on the malting floor, providing conditions for the promotion of germination, namely 24°C over a period


Figure 1 Flow chart for whiskey manufacture.


Figure 1 Flow chart for whiskey manufacture.

Table 1 Processing Steps and Application Principles for Whiskey Processing

Stages of processing

Application principles

Raw material

Pretreatment before mashing







Starch content

Amylases; h-glucanase; proteases; starch gelatinization

Hydrolysis of starch; solubilization of sugars and amino acids

Ethanol formation

Recovery of ethanol

Flavor development

Mixtures of malt and grain whiskies

Dilution of matured spirit of 8 to 12 days. Temperature control is critical and the temperature is maintained either by constant manual turning of the spread grain or by large drums that have cool air blown through them. This germination procedure results in an increase in the levels of the activities of the a-amylase and h-amylase enzymes. These enzymes catalyze the hydrolytic breakdown of starch and are specific towards the a-1,4-glucosidic linkages of the amylose and amylopectin components of starch. They differ in their modes of action: a-amylase carries out internal random hydrolysis, whereas h-amylase removes two glucose residues at a time from the nonreducing end of the polysaccharide chain. The principal end-product of the joint action of a- and h-amylases upon starch is the fermentable sugar maltose. Some dextrin is also produced because neither of these amylases hydrolyzes the a-1,6-glucosidic linkage branch points of amylopectin.

Malting also encourages the development of h-glucanase and protease activities. These enzymes act on components of the starchy endosperm (84% of the total barley grain), respectively the endosperm cell wall structure and the storage proteins (12% of the raw cereal on a dry-weight basis), to enable germination to take place.

The sprouted grain is subjected to kilning, in which the grain is heated gradually to approximately 52°C in order to stop germination but not to destroy the enzymes. In the manufacture of Scotch, the germinated barley (malt) is dried in the presence of smoke rising from a peat fire situated 10 to 15 feet below the malt. The smoke contributes a special peaty flavor (in chemical terms, phenolic compounds, specifically phenol, isomeric cresols, xylenols, and guaiacol) to the malt. At the end of the kilning step, the moisture level of the malt has declined to approximately 5%. The conditions of malt drying favor the Maillard reaction, which contributes to browning and to flavor development. The dry malt may be stored until required.

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