Using the thermodynamic model at zero temperature and a density-dependent quark mass model of confinement, the possibilities of light-quark liberation and strange-quark formation near ground-state nuclear matter have been investigated. Some thermodynamic properties of strange quark matter which may be produced at the core of neutron stars have been studied. The possibility of quark-hadron phase transition in the early Universe has also been investigated using a modified version of a density-dependent confinement mechanism at finite temperature.