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The marketing of poultry livers is only authorized as fresh, frozen, or deep-frozen. The higher consumer demand for these products for a short period of time may lead to the marketing of frozen-thawed poultry livers: this constitutes fraud. The aim of this study was to design a method for distinguishing frozen-thawed livers from fresh livers. For this, the spectral fingerprint of liver proteins was acquired using Matrix-Assisted Laser Dissociation Ionization-Time-Of-Flight mass spectrometry. The spectra were analyzed using the chemometrics approach. First, principal component analysis studied the expected variability of commercial conditions before and after freezing-thawing. Then, the discriminant power of spectral fingerprint of liver proteins was assessed using supervised model generation. The combined approach of mass spectrometry and chemometrics successfully described the evolution of protein profile during storage time, before and after freezing-thawing, and successfully discriminated the fresh and frozen-thawed livers. These results are promising in terms of fraud detection, providing an opportunity for implementation of a reference method for agencies to fight fraud.

The use of proteomics in the field of meat science has gained in robustness and accuracy. This is consistent with the genomic and bioinformatic tools. Its application to sensorial and technological meat quality traits is discussed as well as the emergence of sanitary and nutritional issue which will grow in a next future., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background & Aims: Postprandial lipemia has been associated with inflammation, oxidative stress and vascular dysfunction. This metabolic disturbance represents a complex process only partly understood. The purpose of this study was to identify variations in plasma proteome after a high-fat challenge in healthy middle-aged men., Methods: Two-dimensional electrophoresis was used to compare plasma from seven subjects, drawn before and 4 h after a high-fat challenge., Results: Among the 231 spots detected and analyzed, 22 were present at different levels in postprandial hyperlipemic plasma compared to preprandial plasma. For 10 of them, corresponding proteins were identified by mass spectrometry. Some of them are related to the hemostatic system (tetranectin and fibrinogen) or the complement system (complement component 3 and 4 and ficollin-3) and have been previously associated to atherothrombosis., Conclusion: These results provide new perspectives and broaden our understanding of the biological processes of postprandial metabolic stress, as well as its links with the development of atherosclerosis., (Copyright © 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

Bidimensional electrophoresis was used to compare sarcoplasmic protein profiles of early post-mortem pig semimembranosus muscles, sampled from pigs of different HAL genotypes (RYR1 mutation 1841T/C): 6 NN, 6 Nn, 6 nn. ANOVA showed that 55 (18%) of the total of 300 matched protein spots were influenced by genotype, and hierarchical clustering analysis identified 31 (10% of the matched proteins) additional proteins coregulated with these proteins. Fold-changes of differentially expressed proteins were between 1.3 and 21.8. Peptide mass fingerprinting identification of 78 of these 86 proteins indicates that faster pH decline of nn pigs was not explained by higher abundance of glycolytic enzymes. Results indicate further that nn muscles contained fewer proteins of the oxidative metabolic pathway, fewer antioxidants, and more protein fragments. Lower abundance of small heat shock proteins and myofibrillar proteins in nn muscles may at least partly be explained by the effect of pH on their extractability. Possible consequences of lower levels of antioxidants and repair capacities, increased protein fragmentation, and lower extractability of certain proteins in nn muscles on meat quality are discussed.

Two-dimensional electrophoresis was used to compare Longissimus sarcoplasmic protein abundance between two groups (tough meat and tender meat), defined on the basis of extreme Warner-Bratzler shear force values measured on cooked pork. Fourteen protein spots differed in quantity (P<0.05) between the two groups and were identified. Adypocyte fatty acid binding protein and acyl-CoA binding protein involved in lipid traffic and in the control of gene expression regulating cell proliferation and differentiation, and Enoyl-CoA hydratase, aldose reductase and triosephosphate isomerase indirectly related to lipid metabolism were overrepresented in the tender group. The tender group was further characterized by increased levels of proteins involved in protein folding and polymerization (initiation factor elf-3beta, chaperonin subunit 2, profilin II). The results suggest that the lower post-cooking shear force could at least in part be related to muscle adipogenetic and/or myogenetic status of which the possible underlying mechanisms are discussed.

Two-dimensional electrophoresis was used to investigate the effects of a QTL for muscle hypertrophy on sarcoplasmic protein expression in ovine muscles. In the Belgian Texel breed, the QTL for muscle hypertrophy is localized in the myostatin-encoding gene. Based on microsatellite markers flanking the myostatin gene, we compared the hypertrophied genotype with the normal genotype. The average age of the sheep was 3 mo. Among the 4 muscles studied, in the hypertrophied genotype only the vastus medialis was normal, whereas the semimembranosus, tensor fasciae latae, and LM were hypertrophied. In the hypertrophied genotype, these muscles showed upregulation of enzymes involved in glycolytic metabolism together with oxidative metabolism in LM. Certain chaperone proteins, including glutathione S-transferase-Pi, heat shock protein-27, and heat shock cognate-70, were also more highly expressed, probably due to increased use of energetic pathways. Expression of the iron transport protein transferrin was increased. Alpha-1-antitrypsin was the only protein showing a similar pattern of expression (i.e., less expressed) in all 4 muscles of the hypertrophied genotype. It is suggested that transferrin and alpha-1-antitrypsin may interact to reinforce myogenic proliferative signaling.

Two-dimensional electrophoresis was used to investigate sarcoplasmic protein expression in pig Semimembranosus muscles sampled 20 min after slaughter. Two groups (light and dark) of 12 animals were selected from 1000 pigs, based on meat L values measured 36 h postmortem. Twenty-two proteins or fragments (p < 0.05) were differentially expressed. Muscles leading to darker meat had a more oxidative metabolism, indicated by more abundant mitochondrial enzymes of the respiratory chain, hemoglobin, and chaperone or regulator proteins (HSP27, alphaB-crystallin, and glucose-regulated protein 58 kDa). Conversely, enzymes of glycolysis were overexpressed in the lighter group. Such samples were also characterized by higher levels of glutathione S-transferase omega, which can activate the RyR calcium channels, and higher levels of cyclophilin D. This protein pattern is likely to have severe implications on postmortem metabolism, namely, acceleration of ATP depletion and pH fall and subsequent enhanced protein denaturation, well-known to induce discoloration.

Abstract: Gender, rearing environment and breed of sire influenced 50.5% of the matched protein spots of the soluble fraction and some meat quality traits [Kwasiborski, A., Sayd, T., Chambon, C., Santé-Lhoutellier, V., Rocha, D., & Terlouw, C. (2008). Muscle proteome in pigs: Part I: Effects of genetic background, rearing environment and gender. Meat Science]. Multiple regression analyses determined that 1 or 2 proteins explained between 24% and 85% of variability in Longissimus meat quality. Regression models differed between treatment groups, but relationships between proteins and meat quality traits seemed to be related to common underlying mechanisms. Thus, proteins retained in models for ultimate pH, lightness, drip, thawing and cooking loss were related to the glycolytic pathway, phosphate transfer, or fibre type composition. Another model for thawing loss retained proteins related to denaturation of myofibrils or lipid content. The models for redness involved proteins related to post-mortem oxidative activity. Thus, proteins correlated with meat quality traits were related to biochemical mechanisms known to be involved in meat quality. Relative contributions of these mechanisms may vary according to gender, sire breed or rearing environment. [Copyright &y& Elsevier]

Abstract: A 2×2×2 factorial experiment on Longissimus lumborum of 24 pigs found that rearing environment (indoors or outdoors), breed of sire (Duroc or Large White), and gender (female or castrated male) influenced 22, 10, and 88 proteins of the soluble fraction, respectively, containing 220 matched spots in total. Some proteins were influenced by more than one main effect. Outdoor rearing resulted in lower levels of enzymes of the glycolytic pathway suggesting a more oxidative metabolism. Breed of sire slightly altered the balance of enzymes of the glycolytic pathway. Gender had profound effects. In particular, different enzyme levels suggest a more lipid oriented energy metabolism, and a higher extractability of myofibrillar proteins suggest altered control of the contractile apparatus, in castrated males. Differences in extractability did not explain the profound gender effects. Glycogen content, ultimate pH, drip and thawing losses showed main or interactive effects of the three treatment factors. [Copyright &y& Elsevier]