Strange matrix elements in the proton

Recently much interest has been focused on the strange quark content of the proton. This paper reviews the experimental information available and discuss some proposals for complementary indications. The authors investigate the constraints that chiral symmetry imposes on low energy strangeness admixtures into the proton wave function, in the framework of the generalized three flavor Nambu-Jona-Lasinio model. As expected from the conventional quark model picture, we show that strange contributions to scalar, pseudoscalar, axial-vector and vector densities are not negligible but also not dramatically large