What makes homebrew beer taste off, and how to stop it

Brewing your own beer is mostly straightforward, and the thing that catches people out is that a batch can go wrong without anything obviously going wrong, so you open the first bottle expecting your reward and get a mouthful of something that tastes faintly of wet cardboard instead. Nearly every off flavour in a homebrew traces back to one of the same few causes, and once you know what each one tastes like you can work backwards from the glass to the mistake.

Sanitation, and this is the big one

Bacteria and wild yeast get into a fermenter through anything you didn't clean properly, and what they leave behind runs from a sour twang through to a musty, damp cupboard sort of flavour that you can't wash out afterwards. Clean the fermenter, the tubing, the airlock and the bottles with a brewery cleaner first, because sanitiser doesn't do its job on a dirty surface, then sanitise with a no rinse product and let everything drain rather than wiping it dry with a tea towel. The wiping is where most people quietly undo the whole job.

Water, and how far down the list it actually sits

Water is most of what's in your beer so it does matter, and for somebody starting out it matters a good deal less than the two faults below it. The one worth acting on is chlorine, which comes through as a plastic or medicinal note that people usually blame on their yeast, and if you can smell chlorine in a glass of tap water then you'll taste it in the beer. Brew with rainwater instead, or swap an empty over on the Mt Lofty water exchange and use that. Everything past chlorine, the salts and the mineral additions you read about on forums, belongs to somebody chasing the last few per cent, and it isn't where a first batch or a tenth batch gets better.

Ingredients that have gone tired

Hops and yeast both fade with age, and stale hops give you a cheesy note that nobody enjoys while tired yeast gives you a sluggish ferment and all the flavours that come with yeast under stress. Keep hops sealed and cold, and buy yeast you're actually going to use rather than yeast that lives in a drawer for a year. If a kit tin has sat in the shed through a couple of summers, the malt inside it has darkened and the beer will taste of it.

Fermentation temperature

This is the fault that ruins more beer in South Australia than anything else, because a fermenter sitting in the laundry through a hot week runs well above where ale yeast is happy, and yeast that's too warm throws fusel alcohols that taste solventy along with esters that come across as banana or nail polish. Put the fermenter in the coolest spot in the house rather than the shed, and stand it in a tub of water with a wet towel over it if you need to pull a few degrees off. The opposite turns up in winter, when a ferment stalls because the yeast has gone cold and sluggish, and that's what a heater belt or a heater plate is for.

Rushing it

Green beer tastes green, and most of the flavours that make a young batch taste harsh are ones the yeast cleans up itself if you leave it alone long enough. Give it the full fermentation and then give it the conditioning time in the bottle as well, because carbonation and flavour both arrive on their own schedule and neither of them is hurried along by you checking.

Oxygen after fermentation

Oxygen is what you want going in at the start and what you very much don't want afterwards, and beer that has picked up air tastes of wet cardboard or of sherry, which is the giveaway. Move the beer gently when you transfer it and keep the filling tube down at the bottom of the bottle so it fills from underneath rather than splashing, and don't leave a big air gap under the cap.

Leaving it sitting on the yeast

When yeast dies it breaks down and hands the beer a meaty, sulphury edge, and the fix is just not leaving a finished batch on the yeast cake for weeks on end. Bottle it once fermentation has genuinely finished, which your hydrometer will tell you and your eyes will not, because a fermenter that has stopped bubbling is not the same thing as a beer that has stopped fermenting.

The two that matter most

If you only fix two things, fix your sanitation and your fermentation temperature, because between them they account for most of the off flavours in a beginner's beer and both of them are free to get right. Nobody's first batch is their best one and there's no version of this hobby where it is, so keep a note of what you did each time and you'll narrow yours down a lot faster than any amount of reading will.

Shop related products

• US-05 Safale Ale Yeast 11.5g. A clean, forgiving ale yeast and a sensible one to keep spare.
• S-04 Safale Ale Yeast 11.5g. An English ale yeast that settles out well at the end.
• S23 Saflager Lager Yeast 11.5g. For lagers, and it wants the cool end of the range to behave.
• Coopers Dextrose 1kg. For priming at bottling, measured properly rather than guessed.

The rest of it is in the beer supplies range.

Did you know we also stock no rinse sanitiser, Brew Sanitize, the hydrometer and test jar, bottle brushes in three sizes and heater belts and heater plates in the shop. They aren't all on the website, so give us a ring on (08) 8536 4333 to check what's on the shelf.

If your tap water is the problem, the Mt Lofty water exchange is the easy fix, and Brewhilder is our homebrew helper if you want to talk a batch through.

More from the brewing bench

• What fermentation actually does, and how to keep yeast happy
• Beer ingredients explained: malt, hops, yeast and water
• How to store your homebrew so it still tastes right

Still learning, and I'd back a clean fermenter over a clever recipe any day of the week.

Cheers,
Candeece