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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Meat Safety and Quality » Research » Publications at this Location » Publication #101623
Title: VARIATION IN PROTEOLYSIS, SARCOMERE LENGTH, COLLAGEN CONTENT, AND TENDERNESS AMONG MAJOR PORK MUSCLES

Author
item Wheeler, Tommy
item Shackelford, Steven
item Koohmaraie, Mohammad

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Historically, pork longissimus has been considered to be relatively tender, thus, little pork tenderness research has been conducted. However, there is growing concern among pork industry leaders that selection for increased pork carcass leanness may have a negative impact on tenderness. The objectives of this study were to compare the tenderness of several major pork muscles and determine the cause of variation in tenderness for each muscle. Muscles evaluated included: triceps brachii (from the shoulder), longissimus, (from the loin), semimembranosus, biceps femoris, and semitendinosus (all from the ham). Trained sensory panelists evaluated tenderness, amount of connective tissue, juiciness, and pork flavor intensity. Connective tissue, muscle shortening, and muscle protein degradation were measured as potential sources of variation in tenderness. Tenderness ratings were highest for semitendinosus and triceps brachii, followed by longissimus, then semimembranosus, and was lowest for biceps femoris. Muscle shortening, protein degradation, connective tissue, and tenderness varied among muscles. Connective tissue, muscle shortening, and protein degradation accounted for 8 to 49% of the variation in tenderness within individual muscles and 72% of the variation in tenderness across all muscles. This information will facilitate development of strategies to improve tenderness of each muscle.

Technical Abstract: The objectives of this experiment were to determine the extent of variation in proteolysis, sarcomere length and collagen content among pork muscles and the association of those factors with tenderness variation among muscles at 1 d postmortem. Twenty-three white composite barrows were slaughtered and carcasses (66 kg) chilled at 0 deg C for 24 h. At 1 d postmortem (because variation in tenderness is maximum), the longissimus (LD), biceps femoris (BF), semimembranosus (SM), semitendinosus (ST), and triceps brachii, long head (TB) were dissected from one side of each carcass and frozen. Trained sensory panelists evaluated tenderness, amount of connective tissue, juiciness, and pork flavor intensity on eight-point scales on grilled (70 deg C) chops. Tenderness ratings were highest (P < .05) for ST (7.2) and TB (7.1), followed by LD (6.4), then SM (5.7), and was lowest (P < .05) for BF (4.0). The simple correlations between LD tenderness and the tenderness of other muscles were .54 (SM), .34 (ST), .36 (TB), and .17 (BF). Total collagen was highest (P < .05) for BF (7.1 mg/g muscle), followed by TB (6.0 mg/g), ST (5.3 mg/g), and lowest for SM (4.5 mg/g) and LD (4.1 mg/g). Sarcomere length was longest (P < .05) for ST (2.5 um) and TB (2.4 um), followed by SM (1.8 um), LD (1.8 um), and BF (1.7 um). Proteolysis of desmin was greatest (P < .05) in LD (39.3%), followed by SM (21.0%) and BF (18.5%), then ST (.2%) and TB .2%). Piecewise linear regression accounted for 72% of the variation in tenderness rating. Variation in collagen, proteolysis, and sarcomere length and the degree of their interaction with one another determine the tenderness of individual muscles.