Relationship between myosin denaturation and the colour of low-voltage-electrically-stimulated beef

The semimembranosus muscles of low-voltage-electrically-stimulated beef carcases when subjected to relatively slow chill-freeze cooling were found to be significantly lighter (paler) than the equivalent muscles from unstimulated controls subjected to the same chilling procedure. There was a significant correlation (r > 0·75) between the lightness as measured by the Hunter 'L' values and the degree of denaturation of the myosin as estimated by differential scanning calorimetry. Hot or cold boning did not have a significant effect on the observed effects. In a further experiment, in which hot-boned meat was subjected to very rapid chilling and freezing, no difference in either colour or extent of myosin denaturation between stimulated and unstimulated samples was seen. However, cold-boned, slow chilled, stimulated samples were still measurably paler than the unstimulated controls. It is concluded that exposure of myosin to relatively high temperatures and pH values of 6 or less induces some unfolding of myosin which probably contributes to the observed 'paleness' of these samples. However, other factors may also contribute to the observed paleness.