Proximate composition and changes in muscle proteins of dried salted abo (Otolithes ruber)

Dried salted abo is a popular fishery product in San Miguel Bay (SMB), Philippines.However, the development of this food product has not been fully explored. In this study,the proximate composition and muscle protein profile of dried salted abo was investigatedafter confirming the molecular identification of abo found in SMB. Sequence analysis of16S ribosomal RNA and cytochrome c oxidase subunit I genes suggested that abo in SMBcould be Otolithes ruber. Abo fillets were brined in 4%, 8%, and 12% salt concentrations(w/w) and sun-dried for 6 and 12 hrs. In both 6 hrs and 12 hrs drying time, moisturecontent decreased in samples brined with 12% salt, suggesting that the salt concentrationcould be lowered between 8–12% with 6 hrs drying time. Additionally, the proteolyticprofiling by SDS-PAGE analysis detected 17 bands in the myofibrillar protein fraction.Subsequent mass spectrometry identified nine proteins, of which the myosin heavy chain,actin, and keratin were degraded while the other proteins remained stable. Moreover, at12% salt concentration, changes in staining intensities in several proteins were observed atboth 6 hrs and 12 hrs drying time. These findings revealed that the applied salting anddrying conditions led to the degradation of myosin heavy chain and polymerization ofactin, in addition to an overall alteration of protein profile, which could affect the textureof dried abo product. Overall, this study demonstrated molecular evidence for speciesidentification of abo for the first time. The information on proximate composition andchanges in the protein profile of dried salted abo obtained from this study could help thelocal dried fish industry develop high-quality dried abo products with low salt content.