IMMUNOLOCALIZATION OF INTERMEDIATE FILAMENT PROTEINS IN PORCINE MEAT - FIBER-TYPE AND MUSCLE-SPECIFIC VARIATIONS DURING CONDITIONING

Two intermediate filament proteins, desmin and vinculin, were immunofl uorescently localised in porcine longissimus dorsi* and iliocostalis muscles up to 7 days post mortem. Changes in tenderness of the m. long issimus and the water-holding capacity of both muscles were also monit ored throughout this storage period. Longissimus muscle shows a rapid decline in the overall intensity of labelling for both desmin and vinc ulin. In contrast to the vinculin labelling, desmin labelling is prefe rentially lost from type IIB muscle fibres in the longissimus muscle. In the redder iliocostalis muscle, the loss of desmin and vinculin lab elling was less rapid and did not show an obvious relation to muscle f ibre type. In one sample with very high water loss, there were indicat ions of greater extracellular space development and delayed loss of in termediate filament labelling. The time course of diminishing intermed iate filament labelling is consistent with previous suggestions that d egradation of these proteins is involved in post-mortem conditioning. The variations within and between muscles shown here may explain some of the variability in their mechanical properties. Additionally, it is suggested that intermediate filament integrity is necessary for the e xpulsion of water from the muscle cells during drip formation. (C) 199 8 Elsevier Science Ltd. All rights reserved.