  We have studied in the mechanical and chemical instabilities as well as the
liquid-gas phase transition in isospin asymmetric quark matter based on the NJL
and the pNJL model. Areas of the mechanical instability region and the
liquid-gas coexistence region are seen to be enlarged with a larger quark
matter symmetry energy or in the presence of strange quarks. Our study shows
that the light cluster yield ratio observed in relativistic heavy-ion
collisions may not be affected much by the uncertainties of the isospin effect,
while the hadron-quark phase transition in compact stars as well as their
mergers is likely to be a smooth one.
