Assessing the Myofibrillar and Connective Tissue Protein Contents and Protein Quality of Beef Tripe

The myofibrillar actin content of adult bovine tripe has been determined from the amounts of N τ -methylhistidine found in acid hydrolysate. Collagen and elastin have also been determined from the amounts of 5-hydroxylysine and isodesmosine present, respectively. The beef tripe contained 13.36% actin and 9.59% myosin, corresponding to 37.9 and 27.1% of the myofibrillar protein (35.3% of the total protein). Beef tripe contained high levels of collagen (20.1%) and elastin (1.0%). Beef tripe provides adequate amounts of all of the essential amino acids (EAA 9 ) ranging from 40.3 to 41.9%, compared to FAO/WHO reference EAA 9 pattern value of 33.9% for a 2−5-year-old child, and it is limited only in tryptophan, reflecting the amount of connective tissue proteins present. Evaluation of protein quality of smooth muscles can be based on a knowledge of their digestibility and FAO/WHO amino acid scoring pattern and of their myofibrillar and connective tissue protein contents. Keywords: Smooth muscle; beef tripe; myofibrillar; myosin; actin; collagen; elastin; assessment; protein quality; amino acids; composition