Application of amaranth protein isolate and hydrolysate on a reduced salt fish restructured product: antioxidant properties, textural and microbiological effects

Summary This work evaluates amaranth protein ingredients [isolate (I) and alcalase‐hydrolysate (H)] acting as antioxidants and binders in restructured fish products. Gel products were obtained after thermal treatment (40 °C, 30 min; 90 °C, 30 min) of different formulations from fish muscle pastes, where salt (2%) was partially or totally replaced by I or H. Antioxidant activity was assessed by conjugated dienes and thiobarbituric acid‐reactive substances (TBARs) measurements during the chilled storage. Textural properties, water‐holding capacity, colour and microbiological quality were evaluated. Reduced‐salt content products containing 2% w/w of I or H partially inhibited lipid oxidation especially at the level of the decomposition of hydroperoxides into secondary products, due to about 50% and 60% of inhibition of TBARs, respectively, was registered. Also, these products showed acceptable microbiological quality and technological characteristics with only minimal changes in properties as gel hardness and colour parameters compared with control products (2% w/w salt). This work demonstrates that the replacement of 2% salt (S2) by 2% amaranth protein isolate (I2) or 2% amaranth protein hydrolysate (H2) in fish restructured products produced a significant reduction in the salt content (about 55%), inhibition in the secondary lipid oxidation products (about 50% after 9 days of storage as can be seen in the figure), and products with satisfactory technological characteristics.