ASSESSMENT OF THE PROTEIN-QUALITY OF SELECTED MEAT-PRODUCTS BASED ON THEIR AMINO-ACID PROFILES AND THEIR MYOFIBRILLAR AND CONNECTIVE-TISSUE PROTEIN CONTENTS

The amino acid profiles and levels of myosin, actin, collagen, and collagen-like proteins in extended composite meats were examined as potential indices to assess protein quality of such products. The myofibrillar and connective tissue protein levels of typical composite meat products were determined from the amounts of N(tau)-methylhistidine and 5-hydroxylysine, respectively, found in their acid hydrolysates. When the sum of the myofibrillar and connective tissue proteins was subtracted from the total protein of these products, the difference was an accurate determination of the nonmeat proteins present. Composite meats varied in their amino acid composition and content of myofibrillar (17.4-52.3%), connective tissue (4.1-19.0%), and nonmuscle protein (2.4-67.2%), depending upon the meat cuts and nonmeat protein ingredients used to formulate them. As the content of collagen increased, three of the nonessential amino acids, glycine, proline, and 4-hydroxyproline, increased while the levels of lysine and other essential amino acids decreased. Calculated protein efficiency ratios ranged from 2.7 to 2.9 depending upon amounts of nonmuscle protein additives present.