Value added fish by-products - Nordic Innovation

Figure 3.5. Sensorial attributes of fish protein isolates made from Arctic charr, saithe and cod, respectively.
Evaluation of the effects of salt concentration, cryoprotectants and chilled and frozen
storage on physical properties of cod protein solutions and haddock protein isolate.
In the second test influence of variation in salt concentration, cryoprotectants and chilled and
frozen storage of cod protein solutions (CPS) and haddock protein isolate (HPI) was measured
with regard to viscosity, colour, water holding capacity and stability (microbial count, TVB-
N). The fish protein solutions and fish protein isolate were extracted from cut-offs of cod
(Gadus morhua) and haddock (Melanogrammus aeglefinus), respectively, using the pH-shift
process.
The results indicate that fish protein solutions and fish protein isolates are affected by
different amounts of additives (salt and cryoprotectants). The physicochemical and
rheological properties of these products depend on the additives and time and temperature of
storage. Using cryoprotectants for CPS and a mixture of salt and sucrose for HPI were
recommended to stabilise these products. The most stable frozen cod protein solution was
with 5% salt and cryoprotectants followed by the solution with 3% salt and cryoprotectants.
To make fish protein solutions that would be stable during frozen storage it is recommended
to add cryoprotectants to the products (preferably containing 3-5% salt) at the end of the pH-
shift process. The cryoprotectants increased the water holding capacity and viscosity
(Brabender and Pascal), decreased the weight loss and improved whiteness in CPS containing
1.2, 3, 5 and 15% salt. Shelf life of fish protein solution containing 3-5% protein can be
extended by thermal processing (pasteurization) but risking the loss of desirable functional
properties of the protein solution.
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