What causes beer to have a "plastic bag burp" taste

I've noticed what I describe as a "plastic bag burp" property in some beers. In short, beer burps after drinking the beer have a slight plastic-y aftertaste.

I notice this most often in home brew and in some less-than-stellar craft beers, but I also notice it in some (but not all) of the classic bavarian hefes (e.g. Weihenstephan, Paulaner). Given that weissbier connection I'm wondering if it's a sign of a specific ester or phenolic byproduct, specifically sought for in the bavarian beers, and accidentally produced in the home brews.

I'd love to know what specifically that taste might be coming from, and for bonus points how to avoid it when it's not true to the beer style's taste profile.

Topic weiss taste homebrew

Category Mac

1
answered at

I also detected this plastic burp off flavor. I have a vienna lager with this problem. I encountered with it earlier in a german roggenbier. I found it as "styrene" off flavor I think it is more or less meet your decription. I found a referance stating, that it is produced some of the yeast strains for example wheat beer strains. And it can be caused also by defective carbon dioxid gas supplies or a wild yeast contamination. Here is a link, you can find it on the second page.

1
answered at

It seems to me that you are describing phenols when you talk about the "plastic bag burp" taste. Phenol production does vary quite a bit from one yeast strain to another with the Bavarian weizen yeasts and many Belgian yeasts producing more desirable phenols. Unwanted phenols produce a medicinal, band-aid, smoky, or plastic aroma and flavor. These are often caused by chlorophenols in the water, improper rinsing of chlorine sanitizers, oversparging, sparging with a pH over 6.0, poor yeast health, and wild yeast contamination.

To avoid these flavors you should use a block carbon filter or campden tablets to remove chlorophenols from your water, use a healthy yeast strain, proper sparging while monitoring temperature and pH, and employ a good rinse of chlorine sanitizers or use a non-chlorine sanitizer.

Using a large yeast starter and controlling your fermentation temperature will also decrease phenol production.

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