Making a malt bill is a balancing act. It’s a part of the recipe a brewer rarely gets right first time because coming at the start of the process means everything you do afterwards will have an impact. And at no point is that more clear than during the mash.
By the time you head to work in the morning, the chances are every brewer in the country has mashed in and is wondering where his next cup of tea is coming from.
Brewdays can take anything from five to twelve hours, and then there’s a lot of cleaning up to do, so it starts absurdly early. Brewing collaboration beers or filming on location usually means we get the first train of the day, but it’s always worth it. The steamy aroma of a mash is, without doubt, my favourite smell in the world. It’s somewhere between a great cask bitter and a cookie fresh from the oven. However long you’ve been a brewer, especially on winter days, you can’t help but lean over the tun and breathe in the delicious, warming steam.
Mashing is the process of extracting flavour and sugar from the malt and introducing water to the beer. Hot water and malt are added to a mash tun – a giant vat with a filter plate at the bottom of it. There, it’s held at the best temperatures for enzymes to break down the starch into sugar, stirred most of the time by hand or machine.
The mash may sound like a giant porridge, but it’s where a huge part of a beer’s character comes from. It’s not just affecting the flavour, aroma and colour that we talked about in the last chapter, either – it controls the mouthfeel of the beer, too, and nailing that is very tricky indeed.
The Goldilocks Theory
If Goldilocks had broken into the bears’ house when they were homebrewing, she would have really had her work cut out. Mostly we talk about temperature when mashing, but there are a lot more variables at play. There’s sugar, enzymes and pH levels for her to judge too. The science of the mash is balancing them to get the perfect malty liquid – or “wort” – for the style of beer you’re making.
It’s worth noting here that no recipe is ever really “finished” – good brewers are always tweaking their processes to refine perceived flaws or to react to a shift in an ingredient. So there’s no right or wrong way to do a particular mash; there are only principles that every brewer interprets in their own way. This variation between styles and ingredients, brewers and breweries, is part of what makes beer so varied and exciting. But it also makes writing about beer almost as hard as brewing it. So cheers, guys.
The Right Amount of Water
The next chapter deals with the kind of water we need to use, but the amount of water in the mash is also key. Enzymes are pretty excitable, so if you don’t water down the grain enough they will go to town on the starch and covert it to sugar rapidly. The problem with that is they might do a half-assed job, and some of the sugar they create won’t be fermentable. The result is a fuller-bodied, sweeter beer. A mash with lots of water will result in a slower conversion, but more fermentable sugar for a drier beer. Neither situation is necessarily better; they are just suited to different styles of beer and brewing. A drier mash, particularly one with higher protein grains like wheat, does run the risk of getting “stuck.”
The Right Temperature
Now here comes the science bit. These enzymes I’ve mentioned only work at certain temperatures, and, inconveniently, they all work at different ones.
We could get bogged down in glucanase and peptidases – all the “ases” – but all we need to know is that these two help keep the beer clear and improve retention of the foamy head. More important to us are the alpha and beta amylases that break down the starch. Think of the alpha as a maniac lumberjack with a chainsaw who is chopping down trees at random, while the beta is a madman with an axe splintering smaller pieces off the trees. The yeast can only consume the small bits, so alpha doesn’t give them much to work with because it chops all kinds of sizes. Beta, meanwhile, chops at the bases and makes lots of little fermentable bits. Beta turns most of the starch to sugar, but it can only reach so high, so a little bit gets missed.
The reason I’m over-investing in this metaphor is because this is where the mouthfeel and lots of the flavour is decided. Because the alpha enzymes like chainsawing at high temperatures (around 70ºC/158ºC) and the betas want to start chopping at cooler ones (around 62ºC/144ºF), the temperature you mash at is vital to the rest of the brew.
If you mash at the lower ranges of the beta zone, you’ll end up with a thinner, drier beer. That’s because the betas broke down most of the thick body-providing starch chains, turning them into sugar that was eaten up by the yeast.
If you mash at a higher temperature, you’ll get fuller-bodied, sweeter beer because the alphas didn’t break down all the chunky chains of starch into sugar, leaving it unfermentable.
Most beers are mashed right in between these two ranges. It gives you the sugar you need while not taking away all the body from the beer. When writing a recipe, this is taken as the standard that the brewer deviates from to tailor his mash to the beer in his head. It may be he is making a big imperial IPA and needs all the sugar he can get, so he’ll mash in low. Conversely, if he’s making a 3.8% session IPA, he’ll mash high to leave some body and unfermented sweetness to inject flavour.
As the temperature ranges are pretty small, accuracy is key – keeping control of the mash temperature, and nailing it at the start (known as the “strike temperature”), is vital to get it like Goldilocks wanted: just right.
The Right Acidity
The enzymes at work in the mash prefer a specific pH, so most brewers aim at between 5.2 and 5.5. That’s pretty much the Golden Rule unless you’re making a sour beer, and even then the drop in pH usually happens during fermentation even when you’re using acidulated malt.
Getting the pH of the mash right is a bit of a battle because the kind of malt you add changes it. Thankfully, most water supplies are slightly alkali and, if you’re lucky, nature can do the work for you because dark malts lower the pH. You can also tweak the mash using brewing salts, but this can have an effect on the flavour of the beer. German brewers—who have to stick to certain rules to adhere to that all-important marketing tool, the Reinheitsgebot—use a little acidulated malt to get the right pH.
The Right Time
You can mash for as long as you want. Usually it’s for around an hour, but for an imperial stout it could be several to convert all the starch. The longer you do it, the more sugar you will extract because the enzymes will have more time to work. A longer mash also allows brewers time to change the temperature of the mash – going through the beta temperatures up to the alpha to break down as much as possible. However, not all mash tuns are set up for this, so most brewers stick to one temperature.
The Right Gravity
Brewing is all about having a clear destination in mind, and in the mash that destination is the correct “original gravity.” This is a measurement of the sugar-to-water ratio in the sugary liquid that is now known as “wort”. Too high and the beer could be more alcoholic than intended, too low and it could be weaker. At the end of fermentation, the “final gravity” – or remaining sugar concentration – is measured and the difference between the two reveals the ABV (alcohol by volume) of the beer.
In homebrewing, the gravity is measured using a hydrometer, which is a long, absurdly thin glass tube that floats in the wort. The original gravity is indicated by how high it sits in the liquid. Ask any homebrewer how many times they have