Food Gels of Fish Protein Isolate from Atlantic Cod (Gadus morhua) By-Products Recovered by pH Shift

Food gels were obtained using fish protein isolate recovered from Atlantic cod (Gadus morhua) by-products using the isoelectric solubilisation/precipitation method. The use of low temperatures (not exceeding 10 °C) at the alkaline solubilisation stage resulted in the production of a fish protein isolate with high-molecular mass (FPI-1), while the use of high temperatures (24 °C) resulted in the production of a fish protein isolate with low-molecular mass (FPI-2). The isolates demonstrated excellent gelling and nutritional properties based on their amino acid profiles. The denaturation temperatures of FPI-1 and FPI-2 determined by DSC were 163.0 and 158.5 °C. The secondary structure of FPI-1 demonstrated a high α-helix content and a low random coil content compared to FPI-2. The high-molecular isolate formed stronger gels than the low-molecular isolate, which is explained by the formation of a dense gel network with small pores of about 250 nm. The recovered cod protein isolates can be successfully used as food ingredients or food additives in the production of gel-like/enriched products.