## 2 An Outline of Proteomics
### Proteomic Analyses in Meat Quality Control  
The general plan of proteomics tools in meat quality monitoring involves (i) animals, treatments or muscles with diverse quality features, (ii) protein extraction, 2-DE, image analysis and statistical investigation, (iii) data assessment and extract of significantly different proteins and (iv) protein identification via MS and interpretation. According to [PERSON] et al. [18], untargeted protein profiling identified 737 proteins in beef exudate using LC-MS/MS and demonstrated a distinct proteome profile primarily affected by the muscle source and slightly impacted by aging. The forty-nine significantly affected proteins have been classified into five groups based on their potential function. Five of the significantly affected proteins were affected by aging, more specifically in the 23 rd day postmortem with structural proteins, and forty-four proteins were affected by muscle type. Moreover, through untargeted proteomics the major proteomes in beef exudate were characterized in relation to meat color and oxidative stability of meat. In beef loin muscle exudate, five proteins were correlated to meat color stability while no proteins in tenderloin muscle exudate were found to be correlated. The majority of the identified proteins from tenderloin and beef loin muscles revealed a correlation to meat oxidative stability [18]. Proteomic analyses on chicken breast fillets with white striping myopathy were carried out with the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) [23]. In particular, 148 differentially abundant proteins were identified in the white striping meats compared to normal non-affected meat. Of those, 43 more and 105 less abundant proteins were identified in the white striping meat compared with normal non-affected meat. Vimentin, which is known as marker of white striping myopathy as well as wooden breast abnormality, was one of the identified upregulated proteins. Several proteomic analyses have been reporting regarding white striping and wooden breast meat in order to understand the protein expression as well as the mechanisms and biochemical pathways behind breast myopathies [24; 25; 26; 27; 28]. Similarly, image analysis of whole muscle proteome gels was used and eight differentially abundant sarcoplasmic and myofibrillar proteins were identified in wooden breast (WB) chicken meat including serum albumin, creatine kinase and others. Proteomic differences in moderate WB meat from the commercial broiler industry in the United States pertaining to oxidation and glycolysis were detected. Figure 2: Classification of proteomics methodologies [6; 21]. More specifically, twenty-two proteins were detected only in chicken breasts with severe wooden breast myopathy. It should be noted that these proteins involved in redox homeostasis repaired the respective oxidative damage in tissue as well as maintained the muscle structure and combatted the inflammatory process [28]. A label-free proteomic analysis was also conducted in order to identify the differences in protein profile between young and older duck breast muscles (60, 300 and 900 days old). To discriminate differences in the meat between young and older ducks, [PERSON] et al. [29] combined metabolomics/proteomics analyses. Three groups were found, 616 differentially expressed proteins were identified and 61 proteins were screened. Among the pathways examined, purine metabolism was uniquely enriched, which regulated flavor improvement. In addition, NME3, RRM2B, AMPD1 and AMPD3 may also be potential targets to distinguish young and older ducks. The results indicated that the oldest meat had a unique biochemical signature providing biomarkers for distinguishing young from older ducks. Furthermore, the impact on the quality of meat and the proteomic profiling of duck breast muscle by riboflavin supplementation was determined [30]. As revealed by the results, riboflavin supplementation activated mitochondrial aerobic respiration.