  Grand Canonical Monte Carlo simulations are used to reproduce the N$_2$/CO
ratio ranging between 1.7 $\times$ 10$^{-3}$ and 1.6 $\times$ 10$^{-2}$
observed {\it in situ} in the Jupiter family comet 67P/Churyumov-Gerasimenko by
the ROSINA mass spectrometer aboard the Rosetta spacecraft, assuming that this
body has been agglomerated from clathrates in the protosolar nebula.
Simulations are done using an elaborated interatomic potentials for
investigating the temperature dependence of the trapping within a multiple
guest clathrate formed from a gas mixture of CO and N$_2$ in proportions
corresponding to those expected for the protosolar nebula. By assuming that
67P/Churyumov-Gerasimenko agglomerated from clathrates, our calculations
suggest the cometary grains must have been formed at temperatures ranging
between $\sim$31.8 and 69.9 K in the protosolar nebula to match the N$_2$/CO
ratio measured by the ROSINA mass spectrometer. The presence of clathrates in
Jupiter family comets could then explain the potential N$_2$ depletion (factor
up to $\sim$87 compared to the protosolar value) measured in
67P/Churyumov-Gerasimenko.
