  We study the complete set of flavor changing hyperon axial current matrix
elements at small momentum transfer. Using partially quenched heavy baryon
chiral perturbation theory, we derive the chiral and momentum behavior of the
axial and induced pseudoscalar form factors. The meson pole contributions to
the latter posses a striking signal for chiral physics. We argue that the study
of hyperon axial matrix elements enables a systematic lattice investigation of
the efficacy of three flavor chiral expansions in the baryon sector. This can
be achieved by considering chiral corrections to SU(3) symmetry predictions,
and their partially quenched generalizations. In particular, despite the
presence of eight unknown low-energy constants, we are able to make
next-to-leading order symmetry breaking predictions for two linear combinations
of axial charges.
