Value added fish by-products - Nordic Innovation

Figure 2.6. A frozen block of fish protein isolate
Protein gels made from protein isolates recovered with the new process from several species
have been shown to have equal and sometimes significantly better gelation properties than
those produced using conventional surimi processing techniques (Choi & J.W 2002;
Kristinsson & Demir 2003; Hultin et al. 2005). The process has also been shown to improve
other functional properties. The process has given excellent results for some cold water
species as well as temperate and warm water species. According to Kristinsson & Hultin
(2003) the alkali treatment of cod muscle proteins improved functional properties
(emulsification and gelation) of cod myosin and myofibrillar proteins.
The FPI made by pH-shift process looks like surimi when it is dewatered and packed (Figure
2.6). It may contain about 14-20% protein and 80-86% water. The quality of this product
depends on several factors such as source of raw material, method of processing, pH, amount
of protein and water content etc.
2.3.1 Utilization of fish protein isolate
Fortification of fish fillet by multi-needle injection of fish proteins, static soaking, or vacuum
tumbling have been reported (Thorkelsson et. al 2008). Fish protein injection is believed to
enhance the yield and improve the frozen stability of fish fillet (Kim & Park 2006).
Experiments on injection of brine containing FPI has been shown to increase weight gain in
cod and haddock fillets by 5-20% and increase in cooking yield has been observed. There are
indications that FPI give higher cooking yield and microbiologically more stable products
than products with injected fish mince (Valsdóttir et al. 2006). Improvements in water holding
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