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Why does my beer smell like rotten eggs?

Why does my beer smell like rotten eggs?


Who likes the smell of rotten eggs in their beer?

No one.


There was a time last year when I went to bottle my beer. I'd just sterilized the bottles within an inch of their lives and I was ready to get the precious amber fluid into them.

And with that first pour into the green glass bottle I got the most rank smell.

It was like I had cracked open a rotten egg and fanned it up my nose! It was disgusting.

My brew was contaminated and I was gutted

There could have been a couple of reasons why the rotten egg smell was happening. That rotten egg smell can usually be identified as the gas hydrogen sulfide.

It is the bi-product of the yeast strain or bacteria that have snuck into your brew (did we ever mention you've got to sanitize your equipment?).

All is not necessarily lost however.

If you are brewing a lager is possible that the taste of the sulphur will reduce or disappear during the lagering process. So basically all you have to do to fix this is let the beer stand for a few more weeks.

The news is not so good if you have a bacterial infection 

When is such news ever good?

In my case I think it was clear that the beer was infected. The smell was pungent and a wee taste test suggested worse things were on offer.

But I was a stubborn bugger and bottled anyway on the off chance a bit of time would let everything sort itself out.

How wrong was I.

The beer I tasted after two weeks was probably the worst thing I have ever put in my mouth and I once lost a drinking game involving a kitchen cloth.... I reckon this bad beer would have made me sick if I had of drank say a glass.

The rest of the brews were opened and tipped out. What was very interesting was there was a massive amount of CO2 / bubbles foam released when each cap was removed. They were giant gushers.  I imagine this was due to the bacteria continuing to work it's own magic on the malt.

Either way, the lesson here as always is to do your absolute best to ensure that you have clean equipment and that you've done your best to sanitize it, and kept it clean during the beer brewing process.

Skunked beer


While we're here talking about ruined beer, let's talk about skunked beer. This is when a chemical reaction happens in the bottled beer due to exposure to sunlight.

So named after the smell a skunk can release, lightstruck beer is caused by the UV radiation in light from the sun and retailer's lights. The so-alpha acids in the beer (which come from hops) are broken down and form a new compound in the beer by joining with any proteins floating around. This compound stinks!

Brown glass is pretty handy at preventing this from occurring but not so much green bottles or clear glass. So, the trick to avoiding skunked beer is clearly to store your beer in the dark.

In summary:
  • If you are brewing a lager, the smell could be 'normal' and may disappear after the beer has been conditioned
  • It could well be your beer is contaminated by bacteria, in which case nothing will save it. Head to the pub for a self pitying pint.
  • Lightstruck or skunked beer can happen when bottled beer is left in sunlight too long.

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