Every brewer knows that the quality of the water used in the production of beer is of paramount importance. Water can provide direct flavour effects and also indirect effects upon mash, wort boiling and fermentation. The water we use for brewing is a mix of various inorganic ions which stem from the environment the water passed through during its journey to your tap or well. The concentrations of these ions vary depending upon geographical location and there can be no doubt that some sources of water are better for brewing than others, but as brewers we have a degree of influence over the make up of the water that enters the mash tun.
The common ions in water and their direct influence on flavour are:
Sodium: contributes a salty taste at a concentration of 150 to 200 mg/l and may be harsh at levels greater than 250 mg/l. At lower levels (up to 100 mg/l) sodium ions can produce a sweetening effect in conjunction with chloride ions.
Potassium: can be salty at concentrations greater than 500 mg/l. Beer is high in potassium which is extracted from malt but it is essentially flavour neutral at these levels. Potassium chloride can be considered as a source of chloride instead of sodium chloride if sodium levels are too high.
Magnesium: can contribute a bitter and sour flavour if above 70 mg/l, though this effect is dependant upon a balance with calcium ions.
Calcium: flavour neutral except for its effects on Mg influence
Iron: gives metallic and astringent flavours at levels as low as 0.5 mg/l and even lower in lighter beers.
Chloride: gives fullness and sweetness with optimal effects between 200 to 400 mg/l
Sulphate: imparts dryness and astringency and increase bitterness. Optimal levels are found from 200 to 400 mg/l
Hydrogen: The effect of hydrogen ions is felt through influence on beer pH. At pH values below 4.0 beer tastes more sharp and acidic and perceived bitterness is increased. Values below this cause increased metallic after taste. Above pH 4.0 effects on mouth coating occur resulting in greater biscuit and toasted flavours noted. Above pH 4.4 mouth coating increases with soapy and caustic characters develop.
A number of brewing texts refer to the importance of chloride/sulphate balance because of the antagonistic effects of these two ions. Studies have shown a shift from 1:1 to 2:1 chloride:sulphate increased the perceived sweetness while a shift in the ratio towards sulphate increased perceived bitterness and astringency. Additions of salts such as calcium chloride and calcium sulphate (gypsum) provide brewers with a means of adjusting this balance thereby adjusting the flavour to suit the style of beer brewed. The indirect effects of ions in water are probably of more significance to the quality and flavour of beer than the direct effects they contribute. These indirect effects are manifested through the interaction of ions with malt constituents and wort components. The main direct effects can be divided into:
Yeast requirements: Fermentation is an immensely complicated combination of enzyme reactions that ultimately result in the production of ethanol, carbon dioxide and small quantities of flavour compounds from the anaerobic metabolism of maltose and other malt constituents. In order for these reactions to go ahead smoothly without the production of undesirable flavour compounds yeast must have all the nutrients required to maintain these essential metabolic pathways. Water provides some these essential ions while others are derived from the grist.
Effects on malt enzymes: Suitable water provides a good environment for the action of malt enzymes during mashing which ensures full extraction of fermentables from the grist. The most significant contribution from water is calcium ions which stimulate and protect malt amylases, in particular protecting them from heat inactivation.
Effects on colloidal stability: The main contribution water makes to colloidal stability is through the addition and action of calcium. Calcium levels of at least 50 mg/l are required for good yeast flocculation while at least 100 mg/l are required for good break formation. During break formation calcium forms complexes with proteins, polyphenols and hop constituents aiding their removal from the wort. This greatly helps with wort clarification and can reduce haze potential in the beer. A further action of calcium involves removal of oxalate in the form of calcium oxalate. Oxalate stems from the malt and too much in the finished beer causes gushing upon opening.
Them beers them beers need calcium
Something worth bearing in mind with respect to calcium concentration is the different stages of the brew that various amounts are required. If you have assessed that a certain addition of calcium sulphate will bring your calcium levels up to the level required to mash effectively, the question must be asked how much of the calcium is left behind in the spent grains, and do you have sufficient calcium left for both effective boiling and good yeast flocculation. It is suggested that calcium levels are depleted by 50 to 60% due to losses in the spent grain. Therefore sufficient calcium should be added to maintain calcium levels throughout the rest of the brewing steps.