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

Production of Scotch and Irish whiskies: their history and evolution 159of organoleptically-important compounds duringmaturation in barrels. Thus, Schidrowitz and Kaye(1905) found increased concentrations ofvolatile acids in aged whiskies, a trend alsodescribed in the report of the Royal Commissionon Whisky and Other Potable Spirits (1909).Several reports followed. Liebmann and Scherl(1949), for example, reported increasedconcentrations of acids, furfural, tannins andcolor with maturation in barrels. The arrival ofthe gas liquid chromatograph and HPLC greatlyaccelerated research on this topic; and morerecent data on chemical changes that take placeduring maturation are described later in thischapter.Maturation of whisky in oak barrels is anexpensive process; and it is hardly surprising thatconsideration has been given to methods foracceleration. Jacobs (1947) described several ofthese methods including pretreatment of the beerwith activated carbon, chemical treatment of thewhisky to convert aldehydes into esters and useof oxidation treatments. Such techniques are notused in the industry, which adheres to thetraditional nature of the whisky-producingprocess.Blending and coloringWhisky manufacturers take great pride in thequality of their straight or blended whiskies andin their ability to maintain the quality of a particularproduct over the years. Blending is conductedby experts who advise manufacturers on mixingor blending large volumes of whisky afterappropriate sniffing and tasting sessions onexperimental blends. Blended whiskies are filledinto re-used barrels after dilution with water (ornot) and stored for a further period of timereferred to as ‘marrying’. The water used fordilution is softened or demineralized, since watercontaining an appreciable concentration of saltscan cause hazes in the whisky (Warricker, 1960).After marrying, and dilution if necessary, the colorof the whisky may be adjusted to the desiredvalue by adding caramel. Some brownishpigment is extracted from the casks, but this maynot be sufficient to provide the desired color.Finally, the whisky is clarified for bottling byfiltration through sheets of cellulose (Simpson,1968). Chill filtration may also be practiced, sinceit removes tannin material from the whisky andprevents subsequent appearance of haze.Effluent disposal and spent grainsrecoveryTraditionally effluents from whisky distilleries weredisposed of in the most convenient manner.Spent grains were retailed, often quite cheaply,to local farmers as animal fodder while pot aleand spent lees were simply discharged into thelocal sewer, stream or river. This is no longer thecase, mainly because of the distiller’s awarenessof the nutritional value (largely the proteincontent) of some of these effluents, and publicawareness of environmental problems arisingfrom uncontrolled disposal of effluents intowaterways. Simpson has described theproduction of ‘distillers dark grains’. Theseprocesses are widely used to dispose of effluentsfrom whisky distilleries, especially where thetraditional methods of disposal are forbidden oruneconomic.Organoleptically important componentsof whiskyModern analytical techniques have enabledmajor advances in the understanding of thecompounds responsible for the organolepticproperties of whiskies. However, the first reportson the nature of flavor-producing compoundsin whiskies antedate the era of gas liquidchromatography by nearly half a century. Twopublications by Schidrowitz (1902) andSchidrowitz and Kaye (1905), dealing exclusivelywith Scotch whiskies, reported on the higheralcohol, acid and ester contents of some 50different brands. They reported analyses ofseveral Campbeltown Scotch malt whiskies. A