|Glenlivet is one of the few Scottish distilleries using hard water,|
but nobody told the AD.
The most important attributes of steeping and mashing water are its hardness, pH, overall mineral content and microbiological purity.
Water hardness means the concentration of multivalent cations in the water, ie the amount of ions with a charge of +2 or more (mainly calcium and magnesium) and it is usually expressed as concentration of calcium carbonate (CaCO3) in the water. Soft water is defined as containing under 40-100 mg/l and hard water over 80-200 mg/l of CaCO3, depending on the source.
The pH (pondus hydrogenii) of water means the activity of hydrogen atoms in the water. The pH value describes the acidity of the water in logarithmic scale, ie pH 4 is ten times more acidic than pH 5 and hundred times more acidic than pH 6.
The malt or grain is another source of acidity in the mash. The darker the roast of the malt, the more acidic it gets. Therefore soft alkaline water is often preferred for brewing pale malts and hard water for darker acidic malts. The malts used in whisky production are as pale as possible to ensure the best alcohol yield. The commonly desired pH for mash is about 5-5,5, a lower pH might cause excessive lactic acid bacteria production and a higher pH a slower or incomplete fermentation. Calcium is the most important mineral affecting both the pH and water hardness. Calcium itself does not taste of anything at usual concentrations, but it lowers the pH, increases water hardness and yeast flocculation and might reduce magnesium making the flavour less sour.
Other important ions in the brewing waters are sodium (Na+) and the common anions; sulphate (SO4-2), chloride (Cl-) and carbonate (CO3-2). Sodium softens the water by decreasing the effect of CaCO3 and at higher concentrations (over 50 ppm) makes the water sweet, or even salty (>150 ppm) and sour (>250 ppm). Sulphate enhances bitter, dry and sulphury flavours, complimenting the hoppy aromas of beers and providing antibacterial influence in both fermentation and bottle-aging, reducing the lactic acid bacteria growth. Chloride enhances malty flavour, but at high concentrations it might give pasty, salty or chlorine aromas. None of Scottish distilleries use chlorinated water for their fermentations.
The local water quality was probably one of the reasons why brewers in Burton-on-Trent and Edinburgh went for bitter highly hopped IPAs (high CaSO4), in Pilzen for light crisp lagers (extremely soft water), in Münich for darker lagers (higher CaCO3), in Dublin for dark stout (high CO3-2, low Na+ and relatively low Ca+2) and in London for dark sweet porter (high CaCO3 and NaCO3).
|Ion concentrations in typical brewing waters (Maltman 2003)|
All rainwater is soft, it is in the water reservoirs it acquires its hardness. The longer the water spends in rivers, lochs or underground aquifers, the more time it has to gain solubles from the ground. The geology also plays a significant part, as hard granite or quartz is less soluble than limestone or chalk and very different from young basalt.
|Glen Elgin||Caledonian||Nort Port|
|Royal Lochnagar||Glen Esk|
Water sources for mashing, hard waters in bold (Modified from Udo, 2006)
Scotland is divided into various different geological areas basically by several southwest-northeast-lines as illustrated below.
|Geology of River Spey (www.snh.org.uk)|
The Moray Firth at the Great Glen Fault there is essentially a river delta with mud and sand carried by the rivers, consisting of especially old red sandstone. The red colour comes mainly from iron, but the porous sandstone is also rich in calcium and magnesium, rendering the water in the Northern Highlands and Orkney significantly harder than in the Speyside. The water of Islay lies somewhere in between.
|Typical waters from Scotland (UisgeSource)|
|Several American distillers believe in hard, low-iron water|
So, fermentation waters affect the quality of mash. The minerals themselves do not significantly distill into the spirit, but they affect the fermentation process before it. Soft water probably produces more faster fermentations and lactic acid bacteria growth generally resulting in heavier spirits, as the harder Highland waters produce cleaner and sweeter spirits. Iron is considered as a fault in brewing water and it is likely to produce less estery, fruity spirits. Zinc might do the same at higher concentrations, but is vital for yeast cells in lower concentrations. Peaty water does not provide enough phenols to render the spirit peaty, but higher amount of organics in the fermentation water does produce more esters and less higher alcohols, probably due to greater bacterial growth and yeast autolysis. Fermentation water quality is important to the quality of whisky, but in a different way it has been marketed.
|Effect of brewing water to the spirit sensory quality (Wilson, 2010)|
REFERENCES AND FURTHER READING
Cribb, S&J. Whisky on the rocks. Earthwise, 1998
Geikie, A. The Scenery of Scotland viewed in connection with its Physical Geology. Macmillan 1887.
Goldamer, T. Brewer's handbook. Apex, 2008
Maltman, A. Wine, beer and whisky: The role of geology. GeologyToday 2003;19;1;22-29
Palmer, J & Kaminski, C. Water, a comprehensive guide for brewers. Brewers Assoc., 2013
Scottish Natural Heritage. http://www.snh.org.uk/pdfs/consults/spey/speyreport.pdf
Wilson, CA et al. The role of water composition on malt spirit quality. Nottingham Univ Press, 2010