Loin steaks from 78 carcasses of A, B, C and E maturities were categorized into three tenderness groups on the hasis of sensory tenderness scores and Warner-Bratzler (W-B) shear force values. Myofibril fragmentation index (MFI), sarcomere length, total and soluble collagen, moisture, fat and pH values were determined for these steaks. Carcass characteristics were also measured. The physical, chemical and sensory values were statistically analyzed to determine the relationship of these values, especially the relationship and the importance of myofibril fragmentation to tenderness of loin steaks. Results of this study showed that myofibril fragmentation index (MFI) accounted for more than 50% of the variation in loin steak tenderness and that myofibril fragmentation was a more important effector of tenderness in loin steaks than collagen solubility or sarcomere length. The steaks used in this study varied widely in marbling degree and maturity; therefore, MFI should be an excellent predictor of broiled loin steak tenderness. Although a number of significant correlations were observed between MFI and carcass characteristics, none of these was of practical importance because they accounted for little of the variation in tenderness.

Four tender and four tough bovine longissimus samples from A‐maturity carcasses and four tender and four tough bovine longissimus samples from E‐maturity carcasses postmortem aged 10‐14 days were used to study calcium‐activated factor activity (CAF), calcium concentration, and the 30,000‐dalton component. Significant differences in CAF and free calcium were not found between tender and tough for CAF and free calcium, although the tough samples had more free calcium. Tender bovine longissimus muscle from A‐maturity carcasses had a 30,000‐dalton component and a high ratio of 30,000‐dalton component to actin, whereas tough did not. In E‐maturity, however, both tender and tough longissimus had a 30,000‐dalton component.

Sane As Above 12. REPORT DATE iacutt l?7k 13. NUMBER OF PAGES-2k. 2gL ASS. (ol U. MONITORING AGENCY NAME A ADDRESSfif dl Iterant from Controlling Ottlce) 15. SECURITY CLASS, (ol Mt rmport) Unclassified 15«. DECL ASSIFIC ATION/ DOWNGRADING SCHEDULE 16. DISTRIBUTION STATEMENT (ol t/lia Raporr) This document has been approved for public release and sale; its distribution is unlimited. 17. DISTRIBUTION STATEMENT (ol (ha abalracf entered In Block 20, It different Imn Report)

Approved fov public release; distribution unlimited. 17 •DISTRIBUTION STATEMENT (ol th-j abmtrect nntered In Block 20. If different from Report fefT, BW^WIWI'l V ";' »TO(™P.'«!W'W ntmapn nm auppi»"^w ««piR^.IAH« **«*:»- .-..... npffRpef i «, «IM ii^iF'wwumipi* iniiiiu i.Hij.iMW.