Welcome to The Certified Beer Nerd with Nigel Ayling — your guide to the geeky side of beer.

Today’s off-flavour is sulphur — one of those aromas that can range from acceptable to downright nasty.

Sulphur compounds show up as rotten egg, struck match, burnt rubber, or even sewer gas. Sounds unpleasant, right? But here’s the twist — not all sulphur is bad.

Some lager strains, especially German pilsner yeasts, naturally produce light sulphury notes during fermentation. In a crisp pils, a faint whiff of sulphur can be normal, even expected, and it usually dissipates with proper lagering. But when sulphur hangs around at high levels, it overwhelms the beer and becomes a flaw.

Causes include stressed yeast, incomplete fermentation, or bacterial contamination. In some cases, packaging issues can trap sulphur compounds that would normally escape during fermentation.

Training your palate for sulphur is straightforward: think of a just-struck match or boiled eggs left in the fridge too long. Once you’ve anchored that aroma, you’ll never miss it.

So next time your lager smells like a matchbox or worse, you’ll know sulphur was the culprit. That’s The Certified Beer Nerd — levelling up your tasting skills, one sip at a time