Recently the use of proteolytic enzymes to tenderize meats has increased tremendously. The enzyme papain has been used extensively in commercial meat tenderizers, but many other enzymes also possess the prerequisite proteolytic activity for meat tenderization. Because of the wide variety of proteolytic enzymes from plant, animal, and microbiological sources, which appear suitable and have been suggested as meat tenderizers, a comparison is desirable.As an integral part of the investigation on papain and meat tenderization being conducted in this laboratory, the relative merits of different proteolytic enzymesb were investigated by digesting rehydrated, ground, freeze-dried biceps fentoris muscle of beef with the various enzymes and then fractionating the component protein fractions of meat by extraction and precipitation techniques. I n order to evaluate the extent and mechanism of digestion, the soluble-nitrogen fraction was separated into solubleprotein nitrogen and non-protein nitrogen, and the insoluble-protein fraction was separated into collagen and elastin. The degree of enzymatic digestion of each fraction and sub-fraction was determined by Kjeldahl nitrogen determinations or hydroxyproline determinations.Very little has been written on the relative activities of different proteolytic enzymes on meat. Essentially, the only information on this subject comes from Gottschall and Kies (5) and Hay, Harrison, and Vail (6), who have reported investigations on meat digestion and tenderization by papain and a commercial papain-constituted meat tenderizer, respectively.Despite the recent investigations by Lampitt, Baker, and Brown (10, 11) on the relative extractive ability of dilute hydrochloric acid and sodium hydroxide solutions in extracting soluble meat proteins, it appeared desirable to extend their investigation to include two additional reagents, 0.5% potassium chloride and 20% urea, which are also used for extracting soluble meat proteins. Soluble proteins have been extracted with urea solutions by Neuman and Logan (15) and Beck and Schormuller ( 3 ) , while 0.5% potassium chloride solution has been used as an extraction medium by investigators at this laboratory in dehydrated meat studies. The sodium hydroxide extraction procedure is essentially that introduced by Lowry, Gilligam, and Katersky (12) and subsequently employed by Prudent (16), Husaini, Deatherage, Kunkle, and Draudt (7, 8) and Baker, Lampitt, and Brown (10, 11). I n comparing extractions with hydrochloric acid and sodium hydroxide, the last group of investigators found sodium hydroxide ' Supported in part by a grant from Adolph's Foundation.The enzymes used in this investigation are papain, bromelin, ficin, trypsin, pepsin, Rhozyme P-11, Protease 15, Rhozyme A-4, and a commercial meat tenderizer containing papain. 21 7
