EFFECT OF ELECTRICAL STIMULATION ON PHYSICAL AND CHEMICAL CHARACTERISTICS OF POSTMORTEM BOVINE MUSCLE CHILLED AT VARIOUS RATES
Abstract
Physical and chemical characteristics of postmortem bovine muscle and the effects of electrical stimulation and early postmortem temperture decline rate were studied. Three experiments were performed: (1) 18 beef carcasses of varying weight and fat thickness were split into sides, one side was electrically stimulated while the second was held as a control, and the rate of temperature decline in each side was monitored; (2) 16 beef carcasses were prepared as in experiment 1, the M. flexor carpi radialis was removed from each side and placed as a pair in one of three temperature decline rate treatments and the rate and extent of shortening was monitored; (3) 16 beef carcasses were prepared as in experiment 1, and the effects of hot-boning and early postmortem temperature decline on palatability characteristics and myofibrillar protein degradation in the M. longissimus, were analyzed. Myofibrillar protein degradation was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electrical stimulation did not significantly alter the rate of temperature decline in the deep round or M. longissimus of beef carcasses of different weight and fat thickness. Electrical stimulation did not affect the extent of shortening in the M. flexor carpi radialis at normal temperature decline rates (10(DEGREES)C at 10 hr postmortem). Cold shortening was less severe in electrically stimuated M. flexor carpi radialis chilled at slightly accelerated rates (10(DEGREES)C within 5 hr postmortem). Hot-boning the M. longissimus did not significantly affect sarcomete length, myofibril fragmentation, Warner-Bratzler shear values, taste panel tenderness, juiciness or flavor, or myofibrillar protein degradation if the muscle was chilled at normal rates. Increasing temperature decline rates of the bovine M. longissimus significantly decreased sarcomere length, myofibril fragmentation, taste panel tenderness, taste panel juiciness and 28,000 to 32,000 dalton proteins while increasing Warner-Bratzler shear values and relative percentage of M-proteins, C-proteins, alpha actinin and troponin-T in myofibrillar protein extracts. Longer aging periods postmortem significantly decreased the relative percentage of M-proteins and C-proteins, alpha actinin, troponin-T, and increased relative percentage of tropomyosin and the 28,000 to 32,000 dalton proteins in myofibrillar protein extracts of bovine M. longissimus as assessed by SDS-PAGE. Electrical stimulation resulted in a significant increase in sarcomere length of M. longissimus chilled at rapid rates (10(DEGREES)C within 2 hr postmortem) but had no effect on muscle chilled at normal rates. Electrical stimulation also significantly increased myofibril fragmentation, taste panel tenderness and 28,000 to 32,000 dalton proteins in myofibrillar protein extracts while it decreased relative percentage of M-proteins, C-proteins, alpha actinin, troponin-T and Warner-Bratzler shear values of bovine M. longissimus. Electrical stimulation enhanced meat tenderness via mechanisms other than avoidance of cold shortening in muscle chilled at normal rates during the early postmortem period and enhanced meat tenderness through a combination of avoidance of cold shortening plus other mechanisms in muscles chilled at slightly accelerated rates. Electrical stimulation did not cause an avoidance of cold shortening nor did it overcome cold shortening-induced toughening in muscles chilled at rapid rates.
Degree
Ph.D.
Subject Area
Livestock
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