Improvement of lipid and phospholipid recoveries from sardine (Sardina pilchardus) viscera using industrial proteases

Enzymatic hydrolysis of sardine viscera by three broad spectrum proteases was investigated using the pHstat method (24 h, pH 8, 50 °C). After hydrolysis, three fractions (sludge, aqueous phase and oily phase) were collected. For each fraction, lipids and phospholipids were quantified and molecular weights of aqueous phase peptides were determined. Under these conditions, the degree of hydrolysis (DH) varied from 1.9% (Flavourzyme), 3.1% (Protamex) and to 3.3% (Alcalase). Dry matter distribution indicated that all hydrolysis performed increased solubilisation of proteins: protein recovery for each hydrolysis ranged from 57.4% to 61.2%. Furthermore, the total lipid content in the liquid parts (oily and aqueous phases) increased (at least 85% of lipids quantified in the raw material are in these phases) which may improve lipid recovery for commercial applications. In addition, these lipids were richer in phospholipids than those extracted by classical chemical extraction, especially after Alcalase hydrolysis.