Review Biomarkers of meat tenderness: Present knowledge and perspectives in regards to our current understanding of the mechanisms involved Ahmed Ouali a, ⁎, Mohammed Gagaoua a,b , Yasmine Boudida b , Samira Becila b , Abdelghani Boudjellal b , Carlos H. Herrera-Mendez a , Miguel A. Sentandreu c a UR370, QuaPA, INRA de Clermont Ferrand Theix, 63122 St. Genès Champanelle, France b INATAA, Université de Constantine, 25000 Constantine, Algeria c Instituto de Agroquímica y Tecnología de Alimentos, CSIC, Avenida Agustín Escardino, 7, 46980 Paterna, Valencia, Spain abstract article info Article history: Received 16 February 2013 Received in revised form 3 May 2013 Accepted 10 May 2013 Keywords: Biomarkers Tenderness Metabolism Muscle cell Meat quality Apoptosis Biomarkers of the meat quality are of prime importance for meat industry, which has to satisfy consumers' expectations and, for them, meat tenderness is and will remain the primary and most important quality attribute. The tenderization of meat starts immediately after animal death with the onset of apoptosis followed by a cooperative action of endogenous proteolytic systems. Before consideration of the biomarkers identified so far, we present here some new features on the apoptotic process. Among them, the most impor- tant is the recent discovery of a complex family of serpins capable to inhibit, in a pseudo-irreversible manner, caspases, the major enzymes responsible of cell dismantling during apoptosis. The biomarkers so far identi- fied have been then sorted and grouped according to their common biological functions. All of them refer to a series of biological pathways including glycolytic and oxidative energy production, cell detoxification, protease inhibition and production of Heat Shock Proteins. Some unusual biomarkers are also presented: annexins, galectins and peroxiredoxins. On this basis, a detailed analysis of these metabolic pathways allowed us to identify some domains of interest for future investigations. It was thus emphasized that mito- chondria, an important organelle in the production of energy from carbohydrates, lipids and proteins are a central element in the initiation and development of apoptosis. It was therefore stressed forward that, in fact, very little is known about the postmortem fate of these organelles and their multiple associated activities. Other topics discussed here would provide avenues for the future in the context of identifying reliable pre- dictors of the ultimate meat tenderness. © 2013 Elsevier Ltd. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 2. Meat tenderization mechanisms: some new features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 2.1. Major events following animal bleeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 2.2. Are mono-nucleated cells the first to die in postmortem muscle? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856 2.2.1. Characteristic features of apoptosis in muscle cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856 2.2.2. Particular structural apoptotic changes in postmortem muscle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 856 2.3. New inhibitors of both caspases and apoptosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857 3. Potential biomarkers of meat tenderness identified up to date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858 3.1. Markers from the glycolytic energy metabolism pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858 3.2. Markers from the oxidative energy metabolism pathway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 859 3.3. Markers involved in cell detoxification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 3.4. Markers from the Heat Shock Protein family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 3.5. Annexins A1 and A6 as potential markers of meat tenderness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 3.5.1. Annexins family: presentation and functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 3.5.2. Annexin A1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861 3.5.3. Annexin A6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861 Meat Science 95 (2013) 854–870 ⁎ Corresponding author at: QUAPA, INRA de Clermont Ferrand Theix, 63122 St. Genès Champanelle, France. Tel.: +33 4 73 62 41 63, +33 6 74 40 06 16 (mobile). E-mail addresses: Ahmed.Ouali@clermont.inra.fr, oualiahmed935@yahoo.fr (A. Ouali). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.05.010 Contents lists available at SciVerse ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci