  The three-flavor chiral expansion for octet baryons has well-known problems
with convergence. We show that this three-flavor chiral expansion can be
reorganized into a two-flavor expansion thereby eliminating large kaon and eta
loop contributions. Issues of the underlying formulation are addressed by
considering the effect of strangeness changing thresholds on hyperon masses.
While the spin-3/2 hyperon resonances are considerably more sensitive to these
thresholds compared to the spin-1/2 hyperons, we demonstrate that in both cases
the essential physics can be captured in the two-flavor effective theory by
terms that are analytic in the pion mass squared, but non-analytic in the
strange quark mass. Using the two-flavor theory of hyperons, baryon masses and
axial charges are investigated. Loop contributions in the two-flavor theory
appear to be perturbatively under control. A natural application for our
development is to study the pion mass dependence of lattice QCD data on hyperon
properties.
