RELATION BETWEEN THE POST MORTAL PH AND ELECTRICAL CONDUCTIVITY (EC) DEVELOPMENT, THE DRIP LOSS AND THE MITOCHONDRIAL RESPIRATORY ACTIVITY IN THE PORCINE LONGISSIMUS MUSCLE OF DIFFERENT PIG GENETICS

摘要

IntroductionThe ability of fresh meat to retain moisture is one of the most important quality characteristics of raw products. It has been estimated that much of the pork produced unacceptably high purge or drip loss (Huff-Lonergan and Lonergan, 2005). The situation in muscle cells upon slaughter is related to the focal anoxia and ischemia resulting, for example, in the activation of calcium-dependent processes (e.g. contraction, glycolysis), acidification, partial denaturation and shrinkage of the myofibrillar proteins and reduction in the amount of water that can be attracted and held by the muscular, mainly myofibrillar proteins (Bertram et al., 2004; Huff-Lonergan and Lonergan, 2005). The most severe drip loss could be found in pale, soft and exudative (PSE) meat from pigs that have a mutation in the ryanodine receptor (RyR)/ calcium-release channel (CRC) of the sarcoplasmic reticulum (SR) (Fuji et al., 1991). In the muscle cells of these pigs the control of the calcium release is impaired and the release of this cation from the SR to the sarcoplasm accelerated - especially after physical stress before slaughter. Due to the relation between calcium and the muscle-to-meat-transition process higher concentrations of this ion cause more rapid contractions, an increase in the rate of muscle metabolism and an accelerated acidification of the tissue. This rapid pH decline leads to a reduced water-holding capacity (WHC) of the tissue (Huff-Lonergan and Lonergan, 2005). The alteration is comparable with the malignant hyperthermia syndrome (MHS) in human. For this reason pigs with the described mutation are also called "MHS positive". Usually the calcium concentration in the sarcoplasm is reduced by ATP-dependent transporter proteins in the SR (SERCA). The mitochondria also influence the sarcoplasmic calcium concentration via calcium-dependent in- and efflux-systems in the mitochondrial membrane (Gunther et al., 2004). Considering this in the present work the changes in the mitochondrial function - especially of the respiration capacity - was investigated in pigs in relation to the post mortal pH and electrical conductivity (EC) development and the drip loss. The objective was to obtain a further understanding of how the muscle mitochondria influence the muscle-to-meat-transition.