All good brewers know the importance of water in the brewing process. An understanding of the basic chemistry and how water influences the process is critical to delivering authentic beers of character. It eases the brewing process through to final package to minimise losses and keeps the yeast healthy. Below are a few words about the role two alkaline metal ions play in this process.
Calcium (Ca) and Magnesium (Mg) being alkaline ions have an impact on alkalinity. However, their impact on the alkalinity of water in relation to brewing beer is marginal, if at all. They play a far greater role in mash enzyme activity, protein and yeast flocculation and pH regulation. When we talk about alkalinity, we refer to the abundance of carbonate and bicarbonate ions expressed as calcium carbonate CaCO3.
When there is a very high level of CaCO3 in the raw water, i.e. greater than 100ppm, it needs to be softened to allow the normal processes of brewing to take place at the correct pH. The high temperature in the hot liquor tank (HLT) disassociates the dissolved CaCO3 to Ca2+ and CO32- ions because the bonding is not strong (remember your chemistry of divalent bonding!).
When cool again, the ions recombine and often come out of solution as limescale. This is temporary softening like in a kettle or boiler. This often contains salts of sulphate too. Our normal softening solution is to add Murphy AMS (Acid Murphy Solution) to the HLT which, being a proprietary blend of food grade hydrochloric and sulphuric acid, preferentially binds with the free ions in the HLT to make solubilised CaSO4 and CaCl2 in the ratio found in Burton water (or that ideal for bitters and IPA’s etc.). The unattached CO32- ions are driven off as CO2 gas. So the brewery water is softened, receives a dose of solubilised brewing ions in the correct ratio and can be topped up with DWB (Dry Water Burtonisation) salts in the mash tun. Residual alkalinity is maintained (between 20 – 50ppm) as CaCO3 to act as pH buffering later in the process.
We know your raw water is already soft at 21ppm (Total Alkalinity includes other salts immaterial to brewing) so no need for AMS treatment as described above. The CaCO3 will disassociate in the HLT as explained but this doesn’t matter because the large volume of H+ ions shortly to be liberated in the mash (from the malt phytin) will not be mopped up by any excess of CO32- ions because they simply aren’t there!
We recommend the extra addition of the salts from the DWB because your water does not have enough CaSO4, CaCl2 and MgSO4. In the high temperature environment of the brewhouse, they do not bind with calcium but as we know, contribute instead to enhance the mashing, wort boiling, protein breaking, yeast health & flocculation and ultimately the mouthfeel and flavour balance which you also influence through your choice of malt, hops, process conditions (time, temperature, etc.) and yeast strain. These latter influences under your control are what differentiate your beers from other breweries using the same liquor treatment regimes. Our recommendation ensures you have the correct balance of these ions to maximise the efficiency of what you’re doing already; using nice malt and a well-balanced liquor.
You know the pH curve of the brewing process, it is well described in the literature. By not addressing the issue of alkalinity in the way we do it, an excess of CO32- ions flow through the process and as the fresh beer cools into cellaring/maturation will bind with the free H+ ions making H2CO3ultimately raising pH again out with the target spec of 3.9 – 4.2, all your good work undone! It is one of the commonest faults we see in beers where the liquor is not balanced according to our recommendations. It’s why we always stress to the brewer the importance of at least a once per year liquor check and to follow our recommendations!
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