What happens if you aerate mead towards the end of primary fermentation?

[thisissami]

I've read on multiple occasions that it's bad for the mead. What is it that actually happens? Some people have mentioned that your mead can oxidize - what does this mean? I only know of the term "oxidize" from rusting w/ iron - is there a comparable process taking place here?

I ask, in part, because I just aerated my mead late in the primary fermentation process and only afterwards remembered that i'm not supposed to do that! Now I'm curious as to why that is the case.

 

[ESBrewer]

Oxidation is any reaction where one molecule/atom releases electrons (oxidizes) to another molecule/atom (that receives the electrons and 'reduces'). Rusting is just one example of such reactions. Oxygen is especially eager to receive electrons in such reactions and beer/mead is full of flavor and other compounds that may release electrons to oxygen. So yes, there are lots of similar reactions taking place in alcoholic beverages even if there is not much iron.

Oxygen can also encourage yeast growth which may not be good for the taste since fermentation has started, but not sure how this would affect the taste of your mead. In addition, some (unwanted) microbes need oxygen to proliferate and to oxidize compounds (such as ethanol to vinegar) in low alcohol beverages. So in general we want to keep oxygen in minimum, especially post fermentation but most of the time during fermentation as well..

 

[bernardsmith]

Not an expert and I may be completely wrong-headed about this but I think yeast use O2 to bud (reproduce) and the problem is that towards the end of active fermentation there will be virtually no nutrients left for the daughter cells to adequately construct the membranes of their cells and so are unable to transport any remaining sugars through cell walls properly. Those cells then produce all kinds of compounds and chemicals that can result in off flavors. My sense is that yeast cells will latch onto any oxygen and use it up far more quickly than the O2 will bind to the alcohol or sugars or fruit so while in the primary I don't know that there is any real concern about oxidation ("rust"). That changes in the secondary when a) you have racked the mead off most of the yeast and b) remaining yeast have become dormant. Now oxygen will link to the mead itself. Oxidation changes the color of the mead and makes the flavors taste less fresh and bright (in beer they say it makes the beer taste like cardboard but with fruit I think the taste just tastes stale.

 

[thisissami]

Ok cool - thanks for the feedback everyone!!