# Neutrino decoupling but neutron decay?

I am looking into neutrino decoupling in the early universe, which is said to occur when the reactions: $$e^++n \leftrightarrow p+\bar{\nu}$$ $$\nu+n \leftrightarrow p+e^-$$ $$e^-+e^+\rightarrow \bar{\nu}+\nu$$ are prevented from occuring. However after this time the decay if neutrons still occurs: $$n\rightarrow p+e^-+\bar{\nu}$$ I am therefore wondering why neutrino decoupling is not taken to be after this latter reaction stops occurring (some 3 minutes latter) rather then the former three.