At what temperature does enzyme activity stop?
The fridge in which I retard or cold bulk doughs is a mini fridge that tends to fluctuate wildly in temperature and generally just be really annoying to deal with. I've tried to deal with the fluctuations by cranking the cranking the temperature down pretty low (well below 38 degrees F, which I've heard is around where microbe activity all but stops) since I'd rather take the dough out and let it finish proofing at room temperature than let it overproof. But then that got me thinking: the whole reason you retard dough in the first place is to give enzymes the chance to break down sugars in the flour and produce a more complex flavor...but is there a temperature above freezing where even the enzymes slow down too much to make a difference? I mean, enzymes surely slow down with temperature just like organisms but I guess I'm not sure where the "cut off" is. Asking since I've got some pizza dough retarding right now and it seems like, after testing the temperature settings, my uncooperative fridge is forcing me to decide between 33 degrees or 46 degrees...
It really depends on the enzyme, which means it also depends on the organism whence the enzyme. A dough leavened with wild starter might be more active in the fridge because it's got more diverse microflora, as compared to dough with active dry or instant yeast. But enzymes do continue to do their work until they are physically denatured, by ice or heat in the cases of extreme temperatures. So even at 33 degrees they are still doing something, just quite slowly. Hopefully that is a direct answer to your question: enzymes are still active in the fridge, and there is no hard cutoff point above freezing.
Conversely, raising the temperature from cold to not-as-cold will definitely mean a faster fermentation. To help in your decision making, the (very) general rule is that for every temperature reduction of 10 °C, the rate of a chemical reaction decreases by half. So if you are deciding between 33 and 46 °F, a difference of ~7 °C, you could expect that at the lower temperature of 33, it will take somewhere less than twice as long to ferment as it would at 46. Very rough numbers, but I hope not totally unhelpful. I'd leave it to a better baker to opine as to whether over- or under-fermentation is better during the bulk!
Thank you so much! That's kinda what I was finguring, but I wasn't completely certain so your answer definitely cleared things up! I think in that case I'll just toggle in between the two temperatures to reach a middle ground until I can invest in a proper retarding mechanism.