The frozen samples were directly immersed in Carnoy solution and stored at −20 °C for 2.5 h. The same solution was used for the fixation of the fresh unfrozen samples and they were stored at 4 °C for 2.5 h. After fixation, the samples were immersed in pure ethanol for 24 h at −20 °C (4 °C for unfrozen meat) and subsequently brought to room temperature for another 24 h. Following this dehydration step, the samples were immersed in 3 baths of pure toluene (for 60, 60 & 60 min) and then immersed in a bath of pure paraffin at 59 °C overnight. At the end of this stage each sample was embedded in paraffin in order to be trapped in paraffin blocks. Slices (3 μm thickness) were acquired transversally to the fibers of the muscle from the blocked samples with the use of a rotary microtome from the middle height of the sample (Microm HM 340E, Thermo Scientific, Massachusetts, USA).