Whisky Magazine Issue 4
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In the second of his three-part series on what determines the character of malt whisky, Professor Alan Rutherford looks at the effect mashing, fermentation and distillation have on flavour.
In the last issue of Whisky Magazine I described the contribution made to malt whisky character by the raw materials: water, malt and yeast. Now we move to the distillery.
When malted barley arrives at the distillery it is ground or milled. This is simply a crushing of the grains into grist in order to expose their contents to the mashing waters. Whilst poor grinding will reduce distillery efficiency, the mill has no contribution to make to final spirit character. Indeed some observers might argue that the whole mashing process has little affect on character and that mashing is simply a preliminary conversion and extraction of malt sugars. Having studied the mashing process in brewing and distilling, with both traditional and modern equipment, my conclusion is that there are several aspects of the process which can affect spirit character, albeit subtly, and that the wise malt distiller will be cautious about making any changes in this area.
First, the sweet aqueous liquid or wort drawn off from the mash can be anything from very clear to very cloudy, depending upon the design of mash tun or lauter tun and its mode of operation. There is no doubt that cloudy worts contain more yeast nutrients, including oily materials and fatty acids, which not only suppress foaming during fermentation but also increase the production of higher alcohols and esters. This can lead to whisky of a heavier character.
Secondly, and more subtly, there has been a tendency this century to ...