  We describe two independent frameworks which provide unambiguous
determinations of the deconfinement and the decoupling conditions of a
relativistic gas at finite temperature. First, we use the
Polyakov-Nambu-Jona-Lasinio model to compute meson and baryon masses at finite
temperature and determine their melting temperature as a function of their
strangeness content. Second, we analyze a simple expanding gas within a
Friedmann-Robertson-Walker metric, which admits a well-defined decoupling
mechanism. We examine the decoupling time as a function of the particle mass
and cross section. We find evidences of an inherent dependence of the
hadronization and freeze-out conditions on flavor, and on mass and cross
section, respectively.
