PROCESS CHARACTERISTICS AND FUNCTIONALITY OF SARDINE ( SARDINA PILCHARDUS ) MUSCLE PROTEINS EXTRACTED BY A pH-SHIFT METHOD

The pH-shift method is a recent process used to isolate proteins from animal muscle with good functional properties. It can be used to recover proteins from cheap, underutilized sources and/or process byproducts. In this work, sardine (Sardina pilchardus) muscle proteins were extracted using acidic or alkaline-aided solubilization followed by isoelectric precipitation and compared to the traditional surimi process. This work also reports the comparison between centrifugation and filtration, as means of recovering the precipitated proteins. The highest solubilization of sardine proteins was recorded at pH 2.5 (94%) and 12 (98%), while optimum pH for the isoelectric precipitation of the solubilized proteins in both cases was 6. Protein recovery yields were 600g kg -1 for both acidic and alkaline processes, which are considerably higher than that of the traditional surimi process (400g kg -1 ). When centrifugation was replaced by filtration, protein yields were significantly higher (730g kg -1 for the acidic and 800g kg -1 for the alkaline process), while fat reduction was decreased by 10%compared to the use of centrifugation. The proteins recovered after alkaline solubilization process showed better gelling properties compared to the ones recovered after acidic solubilization. The results of this work clearly show that the process of alkaline solubilization and filtration can successfully be employed to recover proteins with good functional properties from sardine mince.