Evaluation and Utilisation of Fish Protein Isolate Products

Table 1: Protein recovery from processing trout by-products by pH-shift technology(Adapted from, Torres et al., 2006)pH(Solubilisation / precipitation)%Protein recovery2.5 / 5.5 89.02.5 / 5.0 81.92.5 / 6.0 85.92.0 / 5.5 91.33.0 / 5.5 86.212.5 / 5.5 84.412.5 / 5.0 77.712.5 / 6.0 83.412.5 / 5.5 82.913.0 / 5.5 88.13.7 Gel strengthThe gel strength is one of the most important attributes of FPI and surimi. Hultin et al.,(2005) compared gel strength of three different forms of fish proteins prepared from pHshiftprocesses and surimi. In his report gel strength of surimi was weaker than FPI fromalkali-aided process and both of them had a stronger gel than protein isolated from theacid-aided process. Table 2 shows the gel strength of different FPI.Table2: Puncture test and fold test values of different types of alkali aided FPISource Types of FPI Punch test values(g×cm)Fold Testvalue1 Cod Fillet 478 51 Cod Minced 304 21 Cod Frame 277 51 Herring Fresh 801 51 Herring Aged 6 days 287.5 31 Herring Frozen 668 51 Farmed catfish Fillet 850 51 Pacific whiting Fillet 248 -2 Cod cut off 274 32 Saithe cut off 199 22 Arctic charr fish frame 30 11-Hultin et al.,2005; 2- Shaviklo et al.,20083.8 WhitenessWhiteness is another of the most important attributes of surimi and FPI and the market is ingeneral most interested in products having high value of whiteness. Kristinsson et al.,(2005) reported higher values of whiteness for FPI made from both acid and alkali processthan surimi for cat-fish. Table 3 shows whiteness and lightness values of different FPI andsurimi.6