Wow - this is an obscure question! Nutmeg was used to enhance the flavour of ale (beer made without hops [houblons]). Nutmeg [muscade] is a dried spice, so it is never used moist [humide], and it doesn't go stale [perdu].
Ale, on the other hand, does spoil [corrompre]. In Chaucerian English, moist also meant fresh [frais].
So the moist/stale reference is to the ale.
I applaud your reading of Chaucer. You'll probably find as much interesting old French in there as English, but none of it will be much good in everyday use...