How can I diagnose dirty taps from drinking a beer?

Question

There's a restaurant I've visited several times where the food is good, but the draught beer often tastes... off. It's hard to describe exactly how the taste is wrong, but the word "musty" comes to mind.

I know it's not the natural taste of the beer because the effect applies to beers I'm familiar with the taste of, such as Sam Adams Boston Lager and Yuengling Lager. It's can't just be a single bad keg, either, because it happened with different beers and on different days (weeks if not months apart from each other).

A friend suggested to me that the restaurant probably had dirty taps, but only based on my description of what happened (basically what I said above) and wasn't able to give me any more information than that. Is it possible to trace the cause of a bad-tasting beer to dirty taps just from drinking it, and if so, how?

Answer 1

Yes, tap lines that aren't cleaned regularly (every few weeks at least) are susceptible to infection, and you can detect these infections by taste or smell alone. Common bacteria involved are Pediococcus acidilactici and and Lactobacillus which Tasting Beer describes as having a buttery or "goaty, sweat socks" like aroma/flavor. I think that probably aligns pretty closely with your "musty" description.

Is it serious? In the sense that it can cause illness, no, at least not these organisms. These are probiotic bacteria similar to what are advertised in some yogurt. However, given that it does speak poorly to the maintenance routines of this establishment, I wouldn't blame you for not wanting to continue to opt for the draft beer, if for no other reason than that it doesn't taste very good.

Lastly, it might be worth a quick friendly word to management. They may not realize that they need to clean their tap lines more frequently, or not realize that it isn't being done. It's an easily fixable problem and if they do take steps to fix it, everyone will be better off.