74 Comparison of certified Arouquesa Protected Designation of Origin beef vs. standard crossbred beef: A proteomic analysis

Abstract

Protected Designation of Origin (PDO) products are gaining importance due to their high quality and increased consumer concerns about sustainability. Arouquesa PDO beef is a local product with valued organoleptic traits that contributes to local heritage and economy in rural regions of Northern Portugal. Proteomic analysis provides insights on important metabolic pathways that can be related to the production system and be used to differentiate PDO beef from beef produced under standard systems such as those used with crossbreds. The aim of this work is to compare the proteome profile of Arouquesa PDO beef with beef from crossbred animals produced under standard conditions. Muscle samples (n = 10) were collected from the abattoir from male weaners slaughtered at 8.5 mo of age: five Arouquesa breed and five Limousine (n = 2) or Charolais (n = 3) crossbreds. Samples were analyzed using 2D-DIGE and spots showing differential accumulation (P-value < 0.05 and fold-change ± 1.5) were selected for identification using in-gel tryptic digest and LC-MS/MS identification. Meat quality parameters (pH, crude protein and total lipids) were also determined. Animal body weight was 62% heavier (P < 0.05) in crossbred animals (214 ± 5.47 kg). Arouquesa beef had reduced crude protein (17.52 ± 1.39 vs. 20.46 ± 1.44 g/100 g meat) and consequently a greater value of total lipids (8.39 ± 1.86 vs. 3.62 ± 2.44 g/100 g meat). Of the 34 protein spots showing differential accumulation, 13 had greater abundances in Arouquesa beef, whereas 21 were increased in the crossbred animals. Some of the up-regulated proteins in the Arouquesa beef are involved in glycolysis (GADPH, GPI, PGM1, TPI, ENO3) or in muscle structure (MYL1, MYLPF). The down-regulated proteins were mostly related to muscle structure (MYLPF, MYL6B, TNNT1), oxygen transport (HBA, HBB) or heat shock proteins (HSPB1). We also found for some proteins several differentially regulated proteoforms between breeds (MYLPF and TPI1), not all regulated in the same way. The proteins involved in glycolysis can indicate a decreased glycolytic potential of Arouquesa muscle leading to reduced glycogen degradation during post-mortem. The proteins related to muscle structure are generally associated with greater growth performances which was not expected as Arouquesa animals had lighter final body weights. However, MYL1 is also associated to increased tenderness as expectable in Arouquesa beef due to the production system based on early slaughter. The greater abundance of proteins related to oxygen metabolism in crossbred animals suggests a greater oxidative capacity which may be related to muscle fiber composition. In conclusion, the proteome profile of Arouquesa breed points to better beef quality traits compared with commercial beef; thus, contributing to increase product valorization. We found different proteins in the two groups related to specific metabolisms showing a breed-specific response allowing the improvement of the PDO products traceability.