  A regularization scheme that explicitly separates vacuum contributions from
medium effects is applied to a Nambu--Jona-Lasinio model with diquark
interactions and in $\beta-$equilibrium. We perform a comparison of this
proposed scheme with the more traditional one, where no separation of vacuum
and medium effects is done. Our results point to both qualitative and
quantitative important differences between these two methods, in special
regarding the phase structure of the model in the cold and dense nuclear matter
case.
