Relationships between raw broiler breast meat colour and Low-Resolution NMR relaxation properties

It is now well established that colour variations from dark, firm and dry (DFD-like) and pale, soft and exudative (PSE-like) poultry meat are associated with variations of water holding capacity (WHC) properties. The study of LR-NMR relaxation properties, and in particular the values of transverse (T2) relaxation, can give relevant information about meat WHC. To assess the existence of a direct connection between meat colour and T2 relaxation, 36 pale (L*>56), 36 normal (L* between 50 and 56) and 36 dark (L*<50) whole breasts (n=108) were selected from a commercial processing plant at 24 h post mortem, using a Minolta Chroma meter CR-300. The limit values were chosen according to the broiler breast meat L* values distribution previously found in the same processing plant. At 24 h post mortem the ultimate pH (pHu) and colour (L*a*b*) were determined on each fillet (n=216). Subsequently, the right fillet from each breast (n=108) was kept intact and used to determine the intact meat cooking loss, tenderness (Allo-Kramer shear) and NMR transverse relaxation. The left fillet (n=108) was ground and used to determine the ground meat cooking loss, tenderness and NMR transverse relaxation. The pHu values of dark, normal and pale groups significantly differ from each other (P<0.01) and confirm that higher pH values (an average value of 6.04) are associated with darker meat (L*=48.3) while lower muscle pH values (5.77) are associated with lighter meat (L*=57.5). Pale breast meat whether intact or ground exhibit the greatest (P<0.01) cooking losses (23.8 and 27.7%, respectively) compared to normal (21.1 and 24.7%) and dark (18.8 and 21.0%) groups. No differences were found in the meat tenderness among the three groups. Linear discriminant analysis of the raw LR-NMR data shows three distinct types of meat according to the colour group. There is a significant correlation between the LR-NMR signal and lightness as assessed by means of the relative standard deviation principle component regression (RSDPCR). The results confirm that extreme colour variations in broiler breast meat, mainly due to the pH effect, are significantly related to its water holding capacity. The highly significant correlation found between LR-NMR signal and meat quality parameters suggests that LR-NMR technique could be adopted to discriminate broiler breast meat properties for further processing.