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Collagen-based chicken skin is being increasingly used in fat reduced meat products as it has good water retaining properties. This study has identified two unique peptide markers of chicken skin collagen, after extraction, and trypsin digest using LC-MS. The assay has very low detection limits for the two peptide markers. The method was validated by analysing the peptides derived from pork and beef collagen in meat and collagen mixtures. The two chicken collagen peptide markers were not found in either beef or pork collagen, and hence were unique to chicken skin. Further work to make the method quantitative is being undertaken.

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Adulteration of meat products using offal is one of the routes of fraud. This paper describes a method developed to detect the presence of pork liver by identifying specific peptide markers from its trypsin digest using  liquid chromatography-mass spectrometry. Although 74 specific peptides were initially identified from thermally processed pork liver, after examining peptides derived from heat processed pate-type products, five specific peptides were chosen as authenticity markers to confirm the presence of pork liver in highly processed meat products.  

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Polish researchers have used an LC-QTOF-MS/MS (Liquid Chromatography - Quadrupole Time of Flight - Mass Spectrometer) approach for detecting and identifying rabbit-specific peptide-markers from thermally processed meat products to differentiate rabbit from other commonly-consumed animal species. The instrument identified 49 heat stable peptide markers from rabbit myofibrillar and sarcoplasmic proteins. When 11 heat treated rabbit based pâtés were analysed, 3 of the 49 heat-stable peptides were consistently detected in all the pâté samples and hence considered robust markers for rabbit. Pork, lamb and chicken-specific peptides were also monitored in the pâté samples, and undeclared chicken was found in two of the pâtés.

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This review by Polish researchers looks at the most recent advances in proteomic LC-MS (Liquid Chromatography-Mass Spectrometry) methods to identify meat species in processed meat products. The review looks at both low and high resolution LC-MS applied to the identification and detection of heat‐stable species‐specific peptide markers. In the case of myofibrillar and sarcoplasmic proteins, LC-MS/MS was able to detect 105 heat stable peptides in processed meat, and in thermally processed samples, myosin, myoglobin, hemoglobin, l‐lactase dehydrogenase A and β‐enolase are the main protein sources of heat‐stable markers. 

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There is a potential for adulteration of emulsion-type sausages with porcine blood plasma because of its low cost, high protein and functional properties. A proteomic method for the detection of porcine blood plasma has been developed by German researchers. After a rapid protein extraction and tryptic digestion, species-specific marker peptides for porcine blood cell proteins (four markers) and plasma proteins (12 markers) were measured by UHPLC-MS/MS. The method was tested on sausages prepared from a variety of pork raw materials spiked with 0.5-5% meat substitution with porcine blood plasma powder, and subjected to different thermal treatments. The 4 plasma peptides were identified as markers for porcine blood plasma addition, and the method could detect down to 0.7% meat substitution, with a 5% error probability for both false positives and negatives.

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Polish researchers have identified unique heat stable peptide markers from soya, cow's milk and egg white using trypsin hydrolysis and LC-Q-TOF-MS/MS. The source of the peptides were main allergenic proteins, namely soya glycinin and β-conglycinin, milk α-S1-casein and the whey protein β-lactoglobulin, as well as egg white ovotransferrin and lysozyme C. These peptides were able to detect undeclared ingredients in poultry products such as sausages, frankfurters and sausages, as an alternative method to ELISA or PCR-DNA methods. This method would be useful for both allergen detection and food authenticity.

Read the full paper at: Peptide markers for soya, milk and egg