489 Understanding the role of connective tissue in the heat-induced changes of meat palatability

Abstract

Variations in the amount and maturity of intramuscular connective tissue (IMCT) have long been recognised as a source of variations in tenderness between different muscles, animal ages and breeds. Meat becomes tougher as cooking temperatures are increased, and the heat-driven denaturation and shrinkage of IMCT has previously been correlated to these changes. It is often assumed that shrinkage of the collagen in IMCT occurs at temperatures in the range of 62–67°C and that this shrinkage drives cooking losses from meat, so contributing to the increased toughness seen in meat cooked above 70°C. This presentation reviews recent evidence contradicting these common assumptions. The IMCT component dominates the shear strength of lightly cooked muscle, but its contribution diminishes above 60°C and the toughness of meat cooked to 70–80°C is dominated by myofibrillar components. Most differential scanning calorimetry (DSC) studies of the heat-denaturation of collagen in the literature using fast heating rates (5–10°C/min) report peak denaturation rates at temperatures between 62–67°C. However, recent DSC data and analysis of the non-equilibrium, multi-step process of collagen unfolding and denaturation based on a Lumry-Eyring model reveals that the process is highly dependent on heating rate and can be completed at temperatures as low as 55–60°C in slow heating regimes, such as found in low-temperature long-time (LTLT) cooking, or sus-vide cooking. Measurements of the denatured but insoluble collagen in perimysium in meat cooked for extended times at 60°C demonstrate the thermal destabiliisation of IMCT in LTLT cooking. Although IMCT can generate large forces if heated isometrically, careful examination of currently available information suggests that there is no evidence to support the idea that collagen shrinkage drives cooking loss from meat.