Ultimate pH and ageing of meat affect the phase behaviour of mixtures of its proteins and iota carrageenan

The phase behaviour in non-gelling temperature condition (45 °C) of mixtures of iota (ι–) carrageenan (0.1%) and salt soluble proteins (0.4%) from 18 bovine M. longissimus dorsi et lumborum (LD) ranging in inherent ultimate pH (pHu) from 5.42 to 6.97 and aged 0, 1, 2, 7, 14, 21 and 28 days post-mortem were determined. Mixtures separated when centrifuged at 200 × g to form soluble/liquid and complex/gelled phases. Complex/gel formation and yield decreased (P < 0.001) with the increase in meat pHu. Meat proteins and ι–carrageenan contents increased in the liquid phase and decreased in the complex/gel phase with increase in meat pHu (P < 0.001). 50% of the mixtures formed complex/gels at pH 6.29. No formation of complex/gel was predicted with meat proteins or ι–carrageenan at pHu ≥6.81 and 7.43 respectively. Ageing of meat did not have a significant effect (P > 0.05) but tended to increase meat proteins and decrease ι–carrageenan complex/gel forming abilities, suggesting the possibility that with meat ageing there were higher tendencies for intra-interactions between meat proteins rather than interaction with ι–carrageenan. Result of phase contrast microscopy and SDS-PAGE of the liquid and complex/gel phases confirmed the outcome of the chemical analyses. Outcomes of this study can be used to formulate “minimally processed” combi-foods of a range of consistencies.

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► Mixtures of meat proteins and iota carrageenan separated into liquid and gel phases.
► Mixtures containing proteins with pH <6.2 separated and ones with pH >6.4 did not.
► The gel formation and yield decreased with the increase in meat pH.
► The gel formation was not significantly affected by meat ageing.
► Proteins that formed the gels include myosin heavy chain, α-actinin, and actin.