Variation of residual glycogen-glucose concentration at ultimate pH values below 5.75

The aim of this study was to investigate the relationship between residual carbohydrate (glycogen-glucose) concentration and ultimate pH of beef. Ultimate pH of longissimus dorsi (LTL), gluteus medius (GM) and semimembranosus (SM) muscles was determined from the left side of 133 Ayrshire bull carcasses. Corresponding muscle samples (about 3 g) were obtained from the sites of the pH measurements. The relationship was curvelinear. At low pH values the total range of residual glucose concentration was up to 73 mmol/kg, maximum being 83 and minimum 10 mmol/kg. The concept of medium-stress beef, where the combination of low ultimate pH and low residual glycogen is an indication of diminished glycogen content at the time of slaughter, is introduced. The potential negative effects of low residual glycogen concentration on the shelf-life of ground beef is discussed.