  We use a simple framework to calculate the time evolution of the composition
of the fallback material onto a supermassive black hole arising from the tidal
disruption of main sequence stars. We study stars with masses between 0.8 and
3.0 $M_\odot$, at evolutionary stages from zero-age main sequence to
terminal-age main sequence, built using the Modules for Experiments in Stellar
Astrophysics code. We show that most stars develop enhancements in nitrogen
($^{14}$N) and depletions in carbon ($^{12}$C) and oxygen ($^{16}$O) over their
lifetimes, and that these features are more pronounced for higher mass stars.
We find that, in an accretion-powered tidal disruption flare, these features
become prominent only after the time of peak of the fallback rate and appear at
earlier times for stars of increasing mass. We postulate that no severe
compositional changes resulting from the fallback material should be expected
near peak for a wide range of stellar masses and, as such, are unable to
explain the extreme helium-to-hydrogen line ratios observed in some TDEs. On
the other hand, the resulting compositional changes could help explain the
presence of nitrogen-rich features, which are currently only detected after
peak. When combined with the shape of the light curve, the time evolution of
the composition of the fallback material provides a clear method to help
constrain the nature of the disrupted star. This will enable a better
characterization of the event by helping break the degeneracy between the mass
of the star and the mass of the black hole when fitting tidal disruption light
curves.

High Energy Astrophysical Phenomena;Solar and Stellar Astrophysics