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Titill

Evaluation and Utilisation of Fish Protein Isolate Products

Útdráttur

protein isolates and develop a ready to eat food product containing fish protein isolate. The objectives were as follows:
1. to study the effects of salt oncentration, cryoprotectants and chill and frozen storages on viscosity, colour and water holding capacity/weight loss of solutions of cod protein
isolate;
2. to determine the effects of cryoprotectants on the functional properties of the haddock
protein isolates;
3. to study if Brabender® viscograph E can be useful in studying rheological behaviour of
fish protein solutions and fish protein isolates, and
4. to develop cooked fish balls based on mince and isolate.
Added 3 and 5% salt to cod protein solutions with 3% protein decreased Brabender viscosity but adding 10 and 15% salt decreased it significantly(P<0.05). Five days storage at +2°C decreased Brabender viscosity of samples with 1.2,3,5,10 and 15% salt (P<0.05) and had no significant effect on weight loss of cod protein solutions with different amount of salt (P>0.05). Storage time also increased whiteness in chilled sample with 5% salt (P<0.05). Applying cryoprotectants to cod protein solutions increased water holding capacity (%) and Brabender viscosity in samples containing 3 and 5% salt (P<0.05) and had no significant effect on whiteness (P>0.05) after 14 weeks of storage at -24°C. Added cryoprotectants changed rheological flow behavior in all solutions except in solutions with 5% salt. WHC decreased during frozen storage. The solution with 5% salt and cryoprotectant was the most frozen stable solution followed by solution with 3% salt and cryoprotectant. The conclusion is that a cryoprotectant and 3-5% salt are needed to make a frozen stable fish protein solution. Adding salt to fresh haddock protein isolate (HPI) with 20% protein, pH 6.4, different amounts of sucrose and also polyphosphate and stored at +2, -18 and -24°C increased WHC, but significantly (P<0.05) decreased viscosity (BU and Pa) and whiteness. Using polyphosphate and sucrose as a cryoprotectant did not affect WHC, viscosity (Pa) of HPI (P>0.05) but it decreased Brabender viscosity (P<0.05). Apart from the viscosity fresh samples with different amount of additives had the same flow behavior (thixotropic). Different amount of additives and also frozen storage time changed under study attributes of HPI significantly (p<0.05). Like the conventional surimi results suggested that the isolated proteins obtained through the pHshift also need cryoprotectants to preserve them against denaturation during frozen storage. Thus adding 1.3% salt and 5% sucrose as an additive to HPI is recommended. Haddock protein isolate with 20% protein and pH 7.4 was added to haddock mince in different proportions (50:50, 25:75) in manufacturing two types of fried fish balls. A mince fish ball product was also prepared as a control. The products were assessed for physical properties and sensory changes within a period of 8 weeks of frozen storage at -18°C. The Brabender viscosity of mince decreased significantly (P<0.05) as added haddock protein isolates to mince increased. Control sample and fish balls containing isolate had the same cooking loss after two thermal settings (P>0.05). Significant differences were seen for grainy and softness texture, colour and frozen storage flavour during sensory evaluation of fish balls that had been stored for 8 weeks at -18 °C (P<0.05). These attributes depended on the proportion of isolate to mince and also freshness level of the mince. This study shows good potential for HPI to be used as an ingredient in mince-based product development.

Birting
10.10.2008


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