Evaluation and Utilisation of Fish Protein Isolate Products

denaturation and oxidisation of haemoglobin that causes a yellow-brownish colour inproducts. Meanwhile high redness values could be attributed to heme proteins in the finalproduct.Like surimi L*, a*, and b* values of haddock protein isolate were affected by amount ofmoisture content and additives. L*, a*, and b* values were similat to the values whichwere reported by Lanier et al. (1991) for surimi indicating that pH-shift process canproduce products with high lightness similar to surimi.Myoglobin and hemoglobin, which are responsible for the yellow and red colour of fishflesh, respectively (Park 1995) may remain in the fish protein isolated by pH-shift process.Oxidation of these proteins in haddock protein isolate, possibly, decreased a* values andincreased b* values in all samples after 12 weeks of frozen storage. The lowest a* and thehighest b* values after 12 weeks of frozen storage were for control sample indicatingadded salt, sucrose, and polyphosphate may decrease oxidation of proteins in samples.3.3 Water holding capacity and weight loss3.3.1 Fresh HPIWater holding capacity in samples without additives and samples containing sucrose andpolyphosphate was the same (P>0.05) after 2 days of storage at +2˚C (Table 4). Samplewith 1.3% salt and 5% sucrose had the highest WHC followed by sample containing 0.8%salt and 3% sucrose (P0.05). Samples with 0.8% salt and 3% sucrose had more weight lossthan samples containing 1.3% salt and 5% sucrose (P0.05) during 12 weeks storage at -18˚C and -24˚C.44