IN-VIVO RAT ASSAY FOR TRUE PROTEIN DIGESTIBILITY AND PROTEIN-QUALITY OF BEEF AND MEAT-PRODUCTS EXTENDED WITH SOY PROTEIN

The protein quality of ten food products including beef, bovine rumen and four meat products extended with soy proteins had been evaluated b y rat feeding experiments; defatted freeze-dried whole egg served as a reference protein. Mean endogenous fecal and metabolic urinary nitrog en amounted to 1.01 and 1.11 mg/g food consumed,, respectively. True p rotein digestibility and biological value of beef averaged 90.3% and 8 2.6%, respectively. The protein qualities of bovine rumen are quite si milar to that of beef. Beef products extended with soy protein are qui te inferior in their true protein digestibilities (81.4-84.6%) and bio logical value (68.8-76.0%) as compared to beef. The utilizable protein of extended meat fluctuated between 22.6-29.3% compared with a mean l evel of 70% in beef.