Protein hydrolysis products from limed splits

A method for preparing hydrolyzed proteins comprising charging water, molecular sulfur dioxide, and tannery limed splits into a cook tank, the sulfur dioxide comprising from about 0.5% to about 5% of the weight of the charged water, continuously charging live steam to said cook tank for a period from about 11/2 to about 3 hours and until said limed splits are converted to a steam hydrolysis product having a Formol Nitrogen value from about 6% to about 9%, while venting said cook tank under throttle to maintain a superatmospheric pressure and an elevated temperature therein, the superatmospheric pressure being between about 40 and about 50 pounds per square inch gauge, and thereafter venting and cooling said charge mixture.