The enzymomology of the malting, milling, mashing and fermentation processes within the Scotch malt whisky industry
The wort from the malted barley used in the Scotch Malt Whisky process must be obtained solely from the activity of enzymes associated with the malted barley. Little or no detailed studies have been reported on the complex mixtures of enzymes found in malted barley, nor their subsequent activity and fate within the Scotch Malt Whisky process. The aims of this study were to determine assay procedures for a total of 17 enzymes, ascertain their suitability within the heterogeneous mixture of a malted barley extract and then establish the enzyme activity levels within the production process. Method development of the assay procedures gave rise to specific assays for 13 enzymes. Especially important were those for a-amylase, using the Phadebas substrate, and the I!-nitrophenyl-maltopentaose substrate for β-amylase. Both assays were found to be specific within the complex mixture of malted barley wort, with all other carbohydrase enzymes active. Enzyme activities between malted barley varieties were studied and compared. This suggested that differences occurred between the enzyme levels of varieties, as well as within a single variety. These may be due to malting conditions or to geographical, environmental and/or climatic factors associated with barley cultivation. The activities and fate of the enzymes were followed during the production process. Although the distillery where the study was carried out employed an infusion mashing system, the results obtained may also be valid in the semi-Iauter/lauter type systems used within the industry. Malted barley enzymes were active during the initial stages of fermentation, but thereafter other enzyme systems were evident. These were most likely associated with yeast and bacteria.