I recently came across an article by the late George Fix, which refers to diacetyl appearing in apparently normal beer:
"a widely observed but little discussed phenomenon occurs when diacetyl appears spontaneously in a beer that seemed to have normal flavors. Strong evidence indicates that this can occur when marginally dysfunctional yeast have been used in the main fermentation -- they tend not to metabolize all the acetolactic acid in the wort. The acetolactic acid spills over into the finished beer and later is oxidized to diacetyl. Mechanical abuse of packaged beer can promote this; headspace air is the oxidizing agent. Elevated temperatures augment the effect. I have seen cases in which wort constituents (melanoidins and tannins), oxidized on the hot side in wort production, were passed on to the final beer, only to play the role of oxidizer there."
-which could describe what happened in some of our beer of late. As our pale ale is bottle conditioned, we have reabsorbed the diacetyl flavours. But is it possible for a bottle conditioned beer to present with oxidised characteristics, as the yeast within the bottled beer functions as an anti-oxidant? And if so, what are these characteristics? I would imagine that they would differ from oxidized characteristics in a filtered, artificially carbonated product like most macro lagers, where there is little or no yeast present.
Would like to hear about your experiences with diacetyl appearing in normal tasting beer - and how you have remedied this.
Simon
for those interested, the article is found here:
"a widely observed but little discussed phenomenon occurs when diacetyl appears spontaneously in a beer that seemed to have normal flavors. Strong evidence indicates that this can occur when marginally dysfunctional yeast have been used in the main fermentation -- they tend not to metabolize all the acetolactic acid in the wort. The acetolactic acid spills over into the finished beer and later is oxidized to diacetyl. Mechanical abuse of packaged beer can promote this; headspace air is the oxidizing agent. Elevated temperatures augment the effect. I have seen cases in which wort constituents (melanoidins and tannins), oxidized on the hot side in wort production, were passed on to the final beer, only to play the role of oxidizer there."
-which could describe what happened in some of our beer of late. As our pale ale is bottle conditioned, we have reabsorbed the diacetyl flavours. But is it possible for a bottle conditioned beer to present with oxidised characteristics, as the yeast within the bottled beer functions as an anti-oxidant? And if so, what are these characteristics? I would imagine that they would differ from oxidized characteristics in a filtered, artificially carbonated product like most macro lagers, where there is little or no yeast present.
Would like to hear about your experiences with diacetyl appearing in normal tasting beer - and how you have remedied this.
Simon
for those interested, the article is found here:
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