  In framework of statistical models, different particle ratios at energies
ranging from $3.5 $ to $200 $GeV are calculated. Assuming that the particle
production takes place along the freeze-out curve, we study the sharp peak in
$K^+/\pi^+$ ratio observed at SPS energy. We study the responsibility of
non-equilibrium quark occupancy of phase space $\gamma_i$ for particle
production. Allowing $\gamma_i$ to take values other than that of equilibrium,
we got a very well description for $K^+/\pi^+$ ratio at all energies. Using the
resulting parameter set, we analyzed the $K^-/\pi^-$, $\Lambda/\pi^+$ and
\hbox{$\Lambda/<\pi>$} ratios. We found that the corresponding peaks all are
located at the same value of energy, $\sqrt{s_{NN}}^{(c)}\simeq7.5 $GeV. At
this energy, the entropy per particle is singular. The saddle-point in entropy
per particle likely refers to critical phenomenon and change in the phase
space.
