Increased light scattering in electrically stimulated beef longissimus muscle fibres contributes to the observed meat colour at grading

Abstract

Context. Electrical stimulation is often used by meat processors to promote fast muscle pH decline and optimise meat quality. Meat colour can be made more acceptable by this process, but how this relates to the microstructure and light-scattering properties of muscle is still unknown. Aims. To investigate the effect of electrical stimulation of beef carcasses on the meat colour at grading and the role of the muscle fibre microstructure and light scattering in determining colour differences. Methods. Electrical stimulation inputs (electrical stimulation inputs (ES), n = 8; no electrical stimulation inputs (NS), n = 8) were applied to beef carcasses from female cattle of approximately 18-24 months of age. ES comprised electrical immobilisation, bleed rail electric simulation and hide puller rigidity probe, which have all been shown to increase pH fall postmortem in beef carcasses. pH fall was monitored, the longissimus thoracis was graded at 20-22 h postmortem and measurements were made of colour, muscle-fibre structure and light scattering. Key results. The decline of pH was increased in ES relative to NS, as indicated by lower pH at 2 h postmortem (5.83 vs 6.86 respectively, s.e. = 0.068; P < 0.05) as well as changes in both chromatic colour a* b* and achromatic (no colour) lightness in the muscle. Chromatic changes were evident as higher grader colour scores, increased redness (a*) and yellowness (b*) with higher levels of oxymyoglobin and lower levels of deoxymyoglobin. Achromatic changes were evident as increased lightness (L*) and surface reflectance (%R) at the meat surface, and increased global brightness within the muscle fibres. Conclusions. Increased lightness and brightness in electrically stimulated muscles were likely to be due to formation of contraction nodes and distortion of muscle fibres, which changed the microstructure of muscle in ways that increased its light-scattering properties. Implications. Consideration of the role of light scattering in determining beef colour at grading will advance understanding of how to improve this important quality trait.

To What Extent Do Low-Voltage Electrostatic Fields Play a Role in the Physicochemical Properties of Pork during Freezing and Storage?

“…In contrast, the b * value is affected only by the freezing temperature and their interaction. In this instance, the L * value’s level directly represents how strongly light is reflected from the muscle surface Table demonstrates that L * values for L-38 and C-38 treated pork were significantly higher than those for L-18 and C-18 treatments ( P = 0.0001).…”

“…In this instance, the L* value's level directly represents how strongly light is reflected from the muscle surface. 22 Table 1 demonstrates that L* values for L-38 and C-38 treated pork were significantly higher than those for L-18 and C-18 treatments (P = 0.0001). In contrast, L* values for L-18 treated pork were significantly higher than those for C-18 treatment in the third and fourth months of frozen storage (P < 0.05).…”