Chapter 11 Production of Scotch and Irish whiskies: their history and ...

Production of Scotch and Irish whiskies: their history and evolution 143Table 1. Raw materials and unit processes used in the production of scotch and Irish whiskies.Scotch malt Scotch grain IrishRaw materials Peated and unpeated Wheat or corn and a small Unmalted barley and unpeated,malted barley proportion of malted barley malted barleyConversion Infusion mash Mash cook followed by Infusion mashconversion standFermentation Distillers yeast and Distillers yeast Distillers yeastbrewers yeastDistillation Two pot stills Continuous still Three pot stillsMaturation At 62 o GL in used charred Up to 67 o GL in used charred At 70 o GL in used charred oakoak bourbon whiskey oak bourbon whisky barrels bourbon whisky barrels or sherrybarrels or sherry casks or sherry casks for at least casks for at least three yearsfor at least three years three yearsspecific gravity of the fermented mash has usuallydropped to below 1.000. In pot still distilleries,the fermented mash or ‘wash’ (beer) is feddirectly to a still known as the wash still, fromwhich the distillates are redistilled in the secondor low wines still. In Ireland, and in one Scotchmalt whisky distillery, a third distillation is carriedout. Finally, the freshly distilled whisky is storedin charred oak barrels for minimum periods oftime that depend on the legislation in theproducing country (Table 1). Scotch malt andIrish whiskies are customarily matured for muchlonger than the legal minimum period.Individual operationsRaw materialsMalted cerealsMalted barley is the principal malted cereal usedin whisky production. Like the brewer, the whiskydistiller uses barley cultivars of the speciesHordeum vulgare L. and Hordeum distichon(Hough et al., 1971). Malted barley is employedas a source of enzymes (principally amylolytic)that catalyze the hydrolysis of starches and insome instances serves as a source of starch thatis converted ultimately into ethanol. These twodemands must be finely balanced. In themanufacture of Scotch malt whisky, where onlymalted barley is used, care must be taken whenthe grain is sprouting during the malting processto ensure that only a limited amount of enzymeactivity is produced. This is because enzyme isproduced at the expense of the fermentablematerials in the grain (referred to as ‘extract’).However in the manufacture of other types ofwhisky, malted barley is often used as the onlysource of amylolytic enzyme in a mash bill thatcontains a high proportion of unmalted grain. Inthis type of whisky production the enzymeactivity of the malted barley must be greater thanthat used in Scotch malt whisky manufacture.Traditionally, barley used in the production ofScotch malt whisky was malted on the distillerypremises using a floor malting system and driedover fires of coke and peat in the pagoda-shapedkilns which are still a feature of these distilleries.To a large extent, this system has beensuperseded by mechanical maltings, whichproduce malt for groups of distilleries. In ordernot to destroy the enzyme activity developedduring malting, a balance must be achieved inthe kiln between drying the green malt to a