Extraction of Sardine Proteins by Acidic and Alkaline Solubilisation

Abstract

Muscle sardine ( Sardina pilchardus) proteins were extracted using acidic or alkaline-aided solubilisation followed by isoelectric protein precipitation and compared to the traditional surimi process. This work reports the results obtained with unwashed and washed sardine mince. The highest solubilisation of sardine miofibrillar proteins was recorded at pH 2.5 (85%) and 11.5—12 (80%) and the isoelectric point was around pH 5—5.5. The global yields achieved were 77% and 73% for the alkaline and acidic processes respectively, which are considerably higher than that of the traditional surimi process ( ca. 28%). The fat content reduction was 65.3% and 51.0% for the proteins recovered after alkaline and acidic solubilisation respectively. A reduction of 91.1% was obtained in the surimi process. However, higher fat elimination was achieved when washed mince was used (95.3% and 99.0% for acidic and alkaline processes, respectively). The protein recovered after both solubilisation processes showed poor gelling properties than surimi but the acidic recovered proteins had the lowest gel strength. The washing of mince did not influence the whiteness of acidic protein recovered but the proteins recovered in the alkaline-aided solubilisation process from the washed mince were whiter.