The effect of aging on the physicochemical, textural, microbial and proteome characteristics of emu (Dromaius novaehollandiae) meat was studied under aerobic packaging (AP) and vacuum packaging (VP) conditions at 4 ± 1C for 9 and 15 days, respectively. Improvement (P < 0.05) in water-holding capacity, myofibrillar fragmentation index and protein extractability with aging was observed in emu meat cubes under both AP and VP conditions. Reduction (P < 0.05) in Warner-Bratzler shear force values was observed on the 6th and 15th day of aging compared with the 0th day in the AP and VP samples, respectively. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed the appearance of 30-kDa protein bands, indicating extensive proteolysis on the 6th day and 9th day of aging in the AP and VP samples, respectively. Proteome analysis using two-dimensional gel electrophoresis revealed significant (P < 0.01) changes in the number of differentially expressed protein spots in the AP and VP samples during aging. PRACTICAL APPLICATIONSEmus are classified as ratites along with ostriches and rheas and are becoming increasingly popular as a source of low-fat, low-cholesterol, iron-rich red meat alternative. The emu industry is looking for science-based information in order to successfully produce and market emu meat. The present work provides information on emu meat quality, aging process, ultrastructure, proteome characteristics and microbial changes. This paper also discusses about the different packaging methods and the shelf life of emu meat. Considering the increasing demand for new source of animal proteins around the world, this paper provides significant information to all ostrich, rhea and emu meat processors.

BackgroundMyoglobin (Mb) is a sarcoplasmic heme protein primarily responsible for meat color and its chemistry is species specific. 4-hydroxy-2-nonenal (HNE) is a cytotoxic lipid derived aldehyde detected in meat and was reported to covalently adduct with nucleophilic histidine residues of Mb and predispose it to greater oxidation. However, no literature is available on characterization of lipid oxidation induced oxidation of Indian water buffalo (Bubalus bubalis) and goat (Capra hircus) myoglobins.MethodsPresent study characterize the Mb extracted from water buffalo and goat cardiac muscles using two-dimensional gel electrophoresis (2DE), OFFGEL electrophoresis and mass spectrometry (MS). Purified buffalo and goat bright red oxymyoglobin were reacted with HNE in-vitro at physiological pH (7.4) and temperature (37 °C) conditions and the formation of oxidised brown metmyoglobin was measured. The Mb-HNE adducts were detected using MALDI-TOF MS, whereas specific sites of adduction was determined using ESI-QTOF MS/MS.ResultsPurified buffalo and goat Mb samples revealed a molecular mass of 17,043.6 and 16,899.9 Daltons, respectively. The 2DE analysis exhibited 65 (sarcoplasmic protein extract) and 6 (pure Mb) differentially expressed (P < 0.05) protein spots between buffalo and goat samples. OFFGEL electrophoresis revealed an isoelectric point of 6.77 and 7.35 respectively, for buffalo and goat Mb’s. In-vitro incubation of HNE with bright red buffalo and goat oxymyoglobin’s at pH 7.4 and 37 °C resulted in pronounced (P < 0.05) oxidation and formation of brown metmyoglobin. MALDI-TOF MS analysis of Mb-HNE reaction mix revealed covalent binding (via Michael addition) of 3 and 5 molecules of HNE with buffalo and goat Oxy-Mb’s, respectively. ESI-QTOF MS/MS identified seven and nine histidine (HIS) residues of Mb that were readily adducted by HNE in buffalo and goat, respectively.ConclusionThe study demonstrated better redox stability of buffalo Mb than goat Mb. Our findings confirm the hypothesis that relative effect of HNE was greater for Mb’s with 12 ± 1 HIS residues than Mb’s with 9 HIS residues and helps meat processors in developing species-specific processing strategies to reduce the color variability.

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