Deformation of collagenous, elastin and muscle fibres in raw meat in relation to anisotropy and length ratio.

The influence of strain directions on the mechanical properties of raw meat samples in a compression test was analysed in relation to the contracted or stretched state and discussed in terms of connective network deformation. When the lateral deformation of a sample is in the direction of muscle fibres, the more the meat has been stretched ante-rigor, the smaller the strain range in which muscle fibres can be solicited alone and the lower the critical compression ratio at which collagenous fibres come under tension. Post-rigor contraction occurring in stretched muscles modifies the relations between muscle fibres and collagenous fibres and increases the critical compression ratio. The greatest post-rigor contractions have been observed in stretched slices of Semitendinosus and Lattissimus dorsi which are high elastin content muscles. This suggests that elastin has a major role in post-rigor contraction. In greatly contracted post-rigor samples, as muscle fibres are wavy, they are not involved at low strains, likewise collagenous fibres around muscle fibres cannot be stressed until the waviness of muscle fibres has been removed. Therefore, in greatly contracted post-rigor samples, the mechanical properties observed at low strains might belong mainly to elastin fibres. When the lateral deformation is perpendicular to the direction of muscle fibres these fibres are not involved and the more the meat has been stretched ante-rigor the higher the critical compression ratio.