Fermentation waters

Glenlivet is one of the few Scottish distilleries using hard water,
but nobody told the AD.

Water is used in several phases of whisky production: steeping, mashing, cooling and dilution. Formerly water mills provided much of the energy needed in many distilleries as well. Distilleries have often been founded into places where water is easily available and it is believed at least in the marketing departments that fresh spring water or picturesque peaty burns play a significant role in the manufacturing process.

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. 

Spring	Burn/River	Loch	Well	Mains
Ardmore	Aberfeldy	Ardbeg	Auchroisk	Devanha
Balvenie	Aberlour	Auchentoshan	Glenlivet	Dundashill
Benriach	Allt-a-bhainne	Bruichladdich	Macallan	Oban
Benromach	Aultmore	Cambus	St Magdalene	Strathdee
Cardhu	Balblair	Cameronbridge	Saucel
Convalmore	Balmenach	Caol Ila	Strathisla
Craigellachie	Benrinnes	Port Dundas
Edradour	Bladnoch	Millburn
Fettercairn	Blair Athol	Garnheath
Glenallachie	Bowmore	Glen Flagler
Glenburngie	Braes	Islabrae
Glencadam	Brora	Killyloch
Glendullan	Bunnahabhain	Kinclaith
Glen Elgin	Caledonian	Nort Port
Glenfarclas	Caperdonich	Port Ellen
Glenfiddich	Clynelish	Provanmill
Glen Garioch	Cragganmore	Pulteney
Glenglassaugh	Daftmill	Riechlachan
Glen Grant	Dailuaine	Rosebank
Glenkinchie	Dallas Dhu	Springbank
Glenmorangie	Dalmore	Longrow
Highland Park	Dalwhinnie	Springside
Longmorn	Deanston	Strathclyde
Mortlach	Glen Albyn	Tobermory
Pittyvaich	Glendronach
Royal Lochnagar	Glen Esk
Strathmill	Glengoyne
Tamdhu	Glenlochy
Tamnavulin	Glenlossie
Teaninich	Glen Mhor
Tomintoul	Glen Moray
	Lochside
	Macduff
	Mannochmore
	Man O'Hoy
	Miltonduff
	Royal Brackla
	Scapa
	Speyburn
	Talisker
	Tomatin
	Tormore
	Tullibardine

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.

Geological map of Scotland (www.scottishgeology.com)

Speyside and the eastern part of Islay lie on the Dalradian rocks, formed about 570 million years ago and consisting mainly of metamorphosed sedimentary mudstone (schist and quartzite) with some granite hills. The rocks are old and resistant, therefore contributing little to the water, rendering it usually very soft, slightly alkaline and low sulphur. Notable exceptions are Glenlivet and Aberlour, which lie on top of granite-rich soil containing some limestone, rendering the water somewhat harder, especially from wells. 

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

However, many distilleries do process the waters they use. Apparently all the distilleries use at least ion-exchange methods for their bottling (dilution) water, but not necessarily for the reduction right after distilling (to bring the new make spirit down to 63.4% abv). None use chlorinated water for mashing or dilution nowadays. In the earlier part of the 20th century local bottling water was used and there were complaints that London water turned the whisky blue and cloudy whereas Speyside water did not, probably due to harder water of London. Although there are several breweries applying reverse osmosis (demineralization) and specifically mineralized (Burtonized) waters, these methods are not used in the distilling industry, or at least they are not made public. Water softening with resins is not used, and it could be detrimental because it tends to increase the sodium levels. Grain distilleries might benefit from hard water, as the calcium induces enzyme activity and lower malt contents and faster fermentations could be possible, although it is not entirely clear whether the mineralization of mashing waters is allowed by the law and the Scotch Whisky Association.

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

Lactic acid bacteria

Lactic acid bacteria (LAB) are a diverse group of bacteria capable of lactic acid production. They are found for example in cheeses, yoghurts or decomposing plants. They are non-respiratory (anaerobic), but tolerate also aeriated environments and can survive high acid (pH 3-6) and high ethanol concentrations. The Lactobacillales can be divided into different genera, such as Lactobacillus, Leuconostoc, Pediococcus, Lactococcus and Streptococcus etc. Of these the Lactobacillus and in lesser extent the Pediococcus are dominant in distillery environment, although many others survive alongside them. The LAB are present in small quantities in the raw materials, especially the grain, but generally the contamination of wort with LAB comes from the distillery environment (pipes, washbacks etc) and therefore the LAB population in whisky distilleries remains quite stable and the dominant strains of LAB are practically unique in any one distillery.

The yeast dominates the early fermentation and LAB starts to grow significantly after about 36-48 hours as the yeast starts to drop out or die. At the start of the fermentation there are usually various types of LAB in the wort, but many of them die out as the ethanol concentration rises. The first LAB to grow are usually heterofermentative ie they metabolise sugars into lactate, acetate and CO2, the most common species being L.fermentum, L.paracasei and L.brevis. The homofermentative LAB, such as L.acidophilus and L.delbrueckii, producing only lactate from sugars appear later after about 70 hours of fermentation.

Microbes in whisky fermentation, MB-stained=dying cells (Priest 2004)

The heterofermenting LAB can also use pentose sugars, which the Saccharomyces cerevisiae can not ferment, so they are not necessarily competitive. The homofermenters use only hexoses and they always reduce the spirit yield a bit, although they can also use the autolysis products of the dying yeast for their metabolism. The usual amounts of LAB at the start of the fermentation (below 10^6 cells/ml) do not affect the spirit yield, but amounts greater than that could cut the yield up to 20%. The usual amount of LAB in the wort are usually 10^4 to 10^5 per millilitre and rise up to 10^9 at the end of a long fermentation.

Growth of lactic acid bacteria in whisky wort (van Beek 2000)

The effect of LAB on the flavour profile of whisky depends on the species and even the strain of the LAB. Also the availability of metabolites via yeast cell death affects the flavour profile. Probably the most important and common effect of LAB is the increase of lactic and acetic acid, which together with sufficient amount of alcohols leads to increased levels of esters. The lower pH also affects the volatility and activity of various aroma compounds during fermentation and distillation.

The yeast cell death allows the LAB to metabolise the autolysis products, for example the cell membranes containing lots of fatty acids. The LAB hydroxylate these fatty acids into gamma- and delta-lactones, especially gammadecalactone and gammadodecalactone, which produce a heavy sweet and fatty aroma also found in tropical fruits (apricot, peach). The use of brewer's yeast in the fermentation leads to faster yeast cell death and subsequently to higher levels of gammalactones with sweet and fatty notes.

The LAB can alter phenolic aromas as they can decarboxylate cinnamic acids to 4-vinyl guaiacol or 4-vinylphenol and further to 4-ethylphenol. Ferulic acid and p-coumaric acid are common cinnamic acids in malted barley and a typical distiller's yeast (DCL M) and most wild yeasts, but not most brewer's yeasts, can decarboxylate them into 4-vinylguaiacols (smoky, spicy, clove). The LAB has the same decarboxylation enzyme, but they can reduce 4-vinylguaiacol further to 4-ethylphenol (guaiacol, barn-yard, band-aid, brettanomyces), which usually softens the smoky aroma. The smoky aromas are dimished especially if the fermentation is allowed to continue longer.

Amounts of guaiacols in whisky fermentation with DCL M+LAB (Van Beek 2000)

	fruity	fatty	green	sweet	sour	sulphury	meaty
L.paracasei	+		+		+
L.plantarum	+		+		-
L.brevis	(-)	+	(-)	++		++	++
L.casei	+	+
L.fermentum	+	+	+
L.acidophilus		+	+
T.delbrueckii (wild yeast)	-	(+)	+	+	-	(-)	+/-

Some effects of LAB and wild yeast on the flavour of new-make spirit (Van beek 2002, Priest 2004, Wilson 2008)

The growth of LAB depends heavily on the cleanliness of the distillery. Most of the LAB from the raw materials die during the malting and mashing and the main source for the LAB is from the pipes and the washbacks. Steel washbacks are easier to clean and probably lead to lower and different LAB colonies in a distillery. Long fermentation times increase the LAB growth, especially after 48 hours. Some distilleries have variable fermentation times, for example shorter during the week and longer over the weekend, which tends to produce slightly different wash profiles. Below is a table about different distillery fermentation practices.

Distillery fermentation times and washback materials (Udo 2006)

Variable fermentation times (usually weekdays/weekends)

REFERENCES AND FURTHER READING:
Booysen C et al. Isolation, identification and changes in the composition of lactic acid bacteria during the malting of two different barley cultivars. Int J Food Microb 2002;76;63-73
Bryce JH et al (ed). Distilled spirits: Production, technology and innovation. Nottingham Univ Press 2008
Simpson KL et al. Characterization of lactobacilli from Scotch malt whisky distilleries and description of L.ferintoshensis. Microb 2001;147;1007-1016
Smit G., et al. Flavour formation of lactic acid bacteria and biochemical flavour profiling of cheese products. FEMS Microb rev 2005;29(3);591-610
Udo M. The Scottish Whisky Distilleries. Black & White 2006
van Beek S, Priest FG. Evolution of the lactic acid bacterial community during whisky fermentation. Appl Microb 2002;68(1);297-305
van Beek S, Priest FG. Decarboxylation of substituted cinnamic aceds by lactic acid bacteria isolated during malt whisky fermentation. Appl Envir microb 2000;66(12);5322-5328
Walker GM, Hughes PS (ed). Distilled spirits, new horizons: energy, environment and enlightenment. Nottingham Univ Press, 2010
Wilson NR. The effect of lactic acid bacteria on congener composition and sensory characteristics of Scotch malt whisky. Thesis Heriot-Watt Univ 2008.