Friday, 6 April 2012

It's all about water - Mash pH

Well, it seems ages since I last wrote.............hang on a minute, it IS ages since I last wrote, 12 weeks or so, in fact!

Well, this post is all about trying to create a light, summery beer. I ended up with this, looking for some light bitterness from Hallertau and a bit of floral stuff from Amarillo.

However, I had noticed that yet again my beer was showing the same character that I wanted to get rid of, that other local brewers were not getting e.g. the beers being brewed over at Totton's Vibrant Forest brewery. What I was getting was astringency when ever I used darker grains, and an over bitter taste. I have my concerns at the various bits of programming that predict your IBUs - they never give the same answers. However, I found out this was probably due to using different volumes of 'batch size' in the Tinseth Equation for predicting bitterness. Even so, what I was getting was not what I thought I should be getting, and I needed to get rid of this 'tang' for this beer.

A little scouting around the internet led me to discover this might have something to do with mash pH. Probably best explained here, mash pH is about how the acidity/alkalinity of your water changes in response to the phosphate being dissolved out of malt upon mashing. Apparently, the ideal mash condition is acidic at pH 5.4 or so. One of the things this can lead to is astringency from darker grains when the pH is too high. Secondly, I found out that in the South, dark beers brew better than light because of the hardness and alkalinity of the water. Clearly, then, I had to investigate the chemistry of brewing water a bit more.

I use bottled Sainsbury's Caledonian Spring water, so thought I would get away with the South of England high pH, hard water chemistry. However, by reading the labels, plugging in the typical composition into a free water chemistry calculator, and adding the last recipe's malt bill, I discovered I mashed at pH 6.4, was deficient in Ca and Mg, and had a sulphate:chloride ratio that suggested 'bitterness may be enhanced'. Bang on!And measuring the pH of the water I've been using, it was well above the 6.8 of my pH strips,

So using the spreadsheet above, I did two things. Firstly, I added salts like gypsum, calcium chloride and Epsom's salts to rebalance the cations and anions in solution, and to establish a better mash pH, I added a small amount of acid malt to lower the pH even more than usual. I could have taken the old fashioned route, and added an acid rest in the mash (this is a low temperature mash, where the pH is significantly lowered by liberating phytic acid, and this was the old way- possibly before any chemist understood what was going on!- that was used by German brewers using the incredibly soft waters of Pilsen).

So, what have I found? Well, nothing I haven't tasted it. I did notice there was not as much crud on the boiler element, as there usually is, although that may not be chemistry, that might just reflect the malt bill. What I DO think is a result of messing about with the water chemistry (apart from getting a pH of 5.2 according to the pH test I ran), was that I have got a few more percent efficiency out of the mash and boil. There is some evidence to suggest that this is also influenced by mash pH, and the result may be that my calculated grain bill was too high (based on previous efficiencies) and I now may have a beer nearer 6% than 5%! If I have also nipped that bitterness thing in the bud, that sounds like a win-win to me!

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