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Mildly moist January – home brewing low ABV beers

Posted on 20th January 2025

It’s that time of year when many of us cut back a little after feasting all through December. There are more low and no-alcohol beers on the shelves than ever, so naturally as homebrewers we want to try making our own!

The challenge

Brewing a true “no alcohol” beer is very tricky as a homebrewer. Alcohol contributes more to beer than you might realise. Importantly, it helps keep beer from spoiling or making you ill. Alcohol – along with hops and the natural acidity of beer – kills a lot of bacteria and micro-organisms that can be quite dangerous. Think about when you get an injection: your skin gets swabbed with ethanol first to make it sanitary.

Alcohol also carries flavour – without it, some malty and hoppy flavours just don’t come through. This is a bit like the use of seasoning in food. A squeeze of lemon on your fish makes the flavours that bit brighter!

The 0.0% and 0.5% beers you see in the supermarket are typically produced using special yeasts that ferment without alcohol, and/or removing alcohol after fermentation. Those speciality yeasts are not readily available to homebrewers, and removing alcohol without completely destroying the flavour of your beer is a complex technical challenge. These beers are also very often pasteurised and sterile-filtered to make them shelf-stable and free from microbes, which again is difficult at homebrew scale.

However, brewing to a lower level of alcohol, say 2-3% ABV, is much more easily done. And you still get a lot of the benefits, including fewer calories in each glass – and less of a hangover!

The lowdown

There are three main ways to get lower ABVs.

The first is to start with a “normal” strength and dilute with plain water. This is the simplest way by far, but you have to be careful not to end up with a watered-down flavour!

When you do your dilution also makes a difference. Diluting a finished beer by more than around 10% volume (e.g. adding 2L water to your 20L batch) will start to noticeably affect the flavour, but it also won’t reduce the ABV as much as you might think – in a 5% beer you’d get down to around 4.5%. Remember you’re not just diluting the level of alcohol, but everything in the beer, including the level of bitterness, its colour, the mineral balance, and the pH level. In general we don’t recommend diluting your finished beer.

However, you can dilute before fermentation without affecting the flavour or balance so much. Diluting after the boil is usual practice for “normal” brewing when you’re a bit over your expected gravity – this is called liquoring back. You can also dilute after the mash, before the boil.

Diluting at these stages can be almost “invisible” in flavour terms, especially if you prepare extra water before brewing and treat it with the same minerals and acids as your main liquor. However, you would still need to add a lot of water to make a significant dent in the final ABV. 2L of water added to 20L wort with a gravity of 1.050 gives you 22L of 1.045 wort – not a huge difference!

The second method is to ferment in a way that produces less alcohol. Alcohol is a byproduct of yeast breaking down sugars in fermentation. So if your yeast doesn’t break down all the sugars in your beer, you get less alcohol.

Wort is made up of lots of different types of sugars, some “simple” – easy to ferment – and some “complex”, which need more work to break down. The four main types of sugar are, from simplest to most complex: glucose, maltose, maltotriose, and dextrins. All yeast strains start fermenting the simplest sugars first and work up to the more complex ones. When the yeast is “full”, it moves onto the next stages of fermentation, where it cleans up the flavours and goes dormant.

The amount of sugars a yeast strain can get through is described as attenuation. The yeasts with the highest attenuation, like saison yeasts or Brett strains, will eat through every gravity point they can get, all the way up into the dextrin sugars.

On the flip side, there are some low attenuating strains that can only ferment the simpler glucose and maltose portions. These are said to be maltotriose negative and are a good choice to produce lower alcohol beers.

home brew whc low rider yeast

Some examples of maltotriose negative yeast strains are:

It might be tempting to try and stop fermentation artificially by dropping the temperature before your yeast has finished by itself. We strongly recommend against this, as the yeast won’t have moved to the later stages of fermentation and you run a high risk of off-flavours in the beer. You are also at risk of fermentation restarting by itself once the beer is packaged – giving you a keg full of foam and making bottles into high explosive devices… you have been warned!

The third way is to have fewer fermentable sugars to begin with. You can achieve this with careful choice of your grain bill and the way you mash.

The obvious route here is to just use less malt in total. However, like diluting, this can make the final beer seem thin or bland. You can also substitute portions of your base malt, which contributes the most fermentable sugars, with specialty malts. You can actually get away with higher proportions of many specialty malts, such as biscuit malt or imperial malt, than you would use at a “normal” strength. The bold flavours they provide would be too much in a full strength beer, but in low ABV they can go some way to filling out the body.

You can also add sugars such as lactose or maltodextrin that regular ale or lager yeasts cannot break down. Lactose, a sugar derived from milk, adds a pleasant sweetness, but in large amounts is naturally quite milky in flavour. You also won’t be able to serve your beer to anyone who is lactose intolerant. Maltodextrin is less sweet and adds a deeper, more malty body. However, in large quantities it can be claggy – used in excess it starts to taste a bit like wallpaper paste!

Sugars like lactose and maltodextrin are best added with around 5-10 minutes left on your boil. We suggest drawing off a small amount of the boiling wort and dissolving the sugars, then adding this back to the main pot. This avoids the sugar clumping and sinking to the bottom of your pot, where it won’t dissolve properly and can easily burn on the element. Trust us, that’s a cleaning job you don’t want…

Adjusting your mash temperature will also affect the amount of fermentable sugars in your wort. The most common mash temperatures, 64-66°C, are used because they extract the most fermentable sugars from the grain. This is good efficiency. Mashing at higher temperatures gives a lower proportion of fermentable sugars and more dextrins, etc. You’ll also see lower efficiency, which means a lower gravity reading when you begin fermentation. While you don’t want this in a full-strength beer, this can be useful for low ABV brews.

However, this needs to be done appropriately for the style you’re brewing. For example, a West Coast IPA needs a crisp, dry finish at whatever ABV you make it. So you’ll want to keep the mash temperatures in the normal range for this type of beer, otherwise it won’t have the drinkability and balance you want.

Finding the balance

We can use all three of these methods in combination to create really flavourful beers at low ABVs: design your recipe to reduce the amount of fermentable sugars, use a low-attenuating yeast strain, and where needed liquor back before and after boiling to hit your gravity targets.

However, there are some other things we need to take into account when designing a low alcohol recipe.

One particular pitfall is bitterness. Alcohol – and the higher amounts of malty body that usually comes with it – balances out the bitterness of hops. If you take away the alcohol and the malt sweetness, those same hops are going to be far too bitter. So you will often need to use fewer hops in a low ABV recipe.

One way to look at this is comparing the IBUs from your hopping to your expected gravity. This is sometimes called the BU/GU ratio (bitterness units / gravity units). Using the right BU/GU ratio for the style you’re producing will keep your bitterness balanced even at very low IBUs.

The simplest way to find the correct BU/GU ratio for the style you’re making is to compare to a full-strength recipe that you enjoy.

For example, our popular Sundialer kit from Verdant Brewery has 29 IBUs and an expected original gravity of 1.050. To get the gravity units, disregard the “1” and just use the number after the decimal point.

IBU ÷ gravity = BU/GU ratio

29 ÷ 50 = 0.58

If you were making a low ABV version of a hazy ale like Sundialer, with your expected starting gravity at 1.030, you would look at the ratio to work out your target IBUs:

gravity x ratio = IBUs

30 x 0.58 = 17.4

So targeting around 17 IBUs in your low ABV recipe will give it the same balance of bitterness as the full-strength version.

It’s also worth being very careful with dry hops. These again will often need to be used more sparingly as there aren’t the other flavours there to balance them, or to mask drying, vegetal, and woody notes. Part of this is the acidity of the beer – because there is less malt and less alcohol, the pH can often be higher (less acidic) than a full-strength beer. Dry hopping raises the pH as well, and at higher pH levels those astringent and “raw” hop flavours are more noticeable.

It can be a good idea to dry hop at lower temperatures, around or below 10°C, to extract fewer of these notes, though you will still probably need less hops overall than a full-strength beer. This one is to taste so you will need to experiment to find your preferred amount.

Another common fault in a low ABV beer is having a thin, watery body. We’ve already discussed some ways to overcome this, by using higher amounts of specialty malts and unfermentable sugars. However, it’s quite easy to go too far the other way too. Too much lactose and/or maltodextrin will make your beer claggy and overly sweet. Too many specialty malts or too high a mash temperature and you can end up with a beer that lacks drinkability. As with all recipes, it’s about getting the right balance of flavours for the style you’re brewing.

It can be also be difficult when making a low ABV beer to know when fermentation is complete. When you’ve used all the tricks in the book to boost your final gravity and reduce attenuation, knowing when the yeast is really done can be tough! And as with all your brewing, a healthy, fully complete fermentation is the key to great tasting beer. We recommend taking multiple measurements over several days and giving extra time for fermentation to be extra sure.

You might also expect fermentation to be quick, given there are less sugars available to the yeast – however, we’ve found that it takes just as long or sometimes even a little longer. This is because the lack of sugars can mean the yeast doesn’t grow as well. It can be a good idea to add extra yeast nutrients to make up for this and make sure your yeast has a good environment to grow in.

Try our kits

We’ve put together two recipe kits to get you started on your low ABV journey – tried and tested at the Malt Miller like all our recipes! We’ve got a low ABV West Coast pale and a low ABV hazy pale, both super drinkable and well-balanced.

You can also check out our video on how we designed these kits, including our tasting notes and what we learned along the way. And don’t forget to subscribe to our YouTube channel for everything home brewing!

author avatar
Robert Neale

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