Production of protein isolate and surimi from silver carp (Hypophthalmichthys molitrix) and survey their gel and powder colorimetric and chemical parameters

The purpose of this study was production of fish protein isolate and surimi from silver carp
(Hypophthalmichthys molitrix) and survey of color characteristics as well as chemical changes
of gel and powders of those products. In this research, proteins were isolated using pH shifts
method. Acidic pH (2.5 and 3.5) and basic pH (11 and 12) were used to produce fish protein
isolate. Three steps of washing cycles were used for surimi production, and in the third step
0.2% NaCl was used for more dehydration. Results showed that the product efficiency for fish
protein isolate was significantly more than the surimi. Furthermore, the produced fish protein
isolate using acidic pH had the highest production efficiency amongst the samples. As a
result, fish protein isolate had more recovery protein content compared to surimi.
Determination of fat content of the samples showed that surimi contained significantly lower
reduction in fat compared to fish protein isolate. Investigation and comparison of color
characteristics (L, a, b) attributed to gel and powder forms of the samples demonstrated that
the produced fish protein isolate using pH 2.5 had the most intense lightness (L parameter)
amongst the other samples. This study clearly showed that the production efficiency of fish
protein isolate was higher than surimi. In addition, due to the process of surimi production,
fish protein isolate had more protein content. The higher reduction of fat content of fish
protein isolate can be considered as an advantage because of possible increase in durability
and safety of the products.
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