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Meat sensory quality is very variable and depends on many interrelated pre- and post-slaughter factors. The objective of this thesis is to explain by a mechanistic view the variation of several meat quality traits coming from different types of cattle (steers, heifers and young bulls) of numerous breeds using muscle characteristics and a list of 21 biomarkers of meat tenderness.
Findings from this thesis provide new insights in the biological mechanisms underlying the development of tenderness, color and pH of beef meat. The first part deals with the effect of cooking temperature and origin of panelists on the scores of meat sensory qualities. The results showed that irrespectively of animal type and origin of the panelists, tenderness and juiciness scores were higher at an end-point cooking temperature of 55°C than at 74°C. In contrast, beef flavor and overall liking scores were higher at 74°C than at 55°C. The second part of the thesis focuses on the relationship between muscle characteristics and sensory qualities. The results mainly show that the activity of the oxidative enzyme isocitrate dehydrogenase (ICDH) and the proportions of the slow myosin heavy chain (MyHC-I) allow discrimination of breeds irrespectively of animal type. However, none of the muscle characteristic was correlated with the evaluated sensory quality traits. The third and principal part of this thesis focuses on the use of the
biomarkers abundances to explain and predict the main meat quality traits. The prediction models taking in to account all young bulls breeds (Aberdeen Angus, Limousin and Blonde d'Aquitaine), explain only a small part (10 - 17%) of the variability of tenderness. However, the prediction power of the models constructed by breed were good, explaining up to 70% of the variability of tenderness of Longissimus thoracis and Semitendinosus muscles of the young bulls. Prediction
models built by muscle and breed showed many differences. Some biomarkers were common to both muscles and/or three breeds. Particularly, Hsp70-1A/B appears as a potential generic biomarker of tenderness, while other proteins were muscle and/or breed specific. In addition, this thesis is the first to show prediction equations of beef meat color and pH using the list of 21 biomarkers. Its originality consists in the use of muscle samples sampled early post-mortem.
Hsp70-1A/B and μ-calpain were highly correlated with each other and with all the meat color parameters. Based on these results, a biological mechanism was proposed to explain this strong correlation, suggesting the involvement of two phenomena: protein oxidation and apoptosis.
Moreover, many biomarkers were correlated with pH45min, pH3h and ultimate pH. Prdx6 was associated with the three parameters of pH and a possible biological mechanism was proposed.
The last part of this thesis focuses on the use of interactomics and shows the correlation networks between the 21 biomarkers studied. The networks identified the metabolic pathways and proteins (DJ-1, Hsp70-Grp75 and small Hsp) which may be strongly linked to meat quality traits irrespective of muscle and breed. Finally, an integrative mechanistic scheme using the biomarkers studied is proposed to describe the mechanisms that govern the steps of post-mortem muscle to meat conversion and preliminary results on the integration of serpins in the list of biomarkers are presented. |
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