treating zone until a temperature of about 310 u00b0 to 350 u00b0 f is reached preferably temperatures of about 325 u00b0 to about 350 u00b0 f are employed the residence time in the confined zone is not critical and may range from a few seconds up to one or two minutes residence time values may be controlled by varying the slurry feed rate and the length of the zone the protein material which has been rendered thermoplastic by the preceding steam treatment next enters a rotating multi orifice spinnerette head located at the discharge end of the confined treating zone the centrifugal forces created along the axis of the spinnerette act to draw stretch and orient the emerging protein monofilaments spinnerette rotations in the range of about 1000 to about 2000 rpm are suitable to form monofilaments optimum results are achieved at about 1800 rpm by varying the spinnerette rpm 39 s and the pressure and temperature conditions in the cooking tube fiber lengths from about 1 2 to about 6 inches can be obtained the spinnerette head further serves to maintain a back pressure of about 70 to 80 psi in the confined zone in the preferred embodiment the fibers emerging from the spinnerette are quenched by sprays of a cooling fluid e g water directed at the product the resulting stream of water is useful to carry the product out of the centrifuge and into a collection zone where.