This study aimed to develop and characterise a fish burger made from mechanically separated tambaqui (Colossoma macropomum) meat and incorporating soy okara as a functional ingredient. Four fish burger formulations were developed and the physicochemical characteristics (moisture, ash, lipid, protein, carbohydrate, and energy), instrumental colour parameters (L*, a*, b*, chroma, and hue angle), microbiological quality (facultative aerobic mesophiles, psychrophiles, moulds and yeasts, total coliforms, thermotolerant coliforms, Escherichia coli, coagulase-positive staphylococci, and Salmonella species), cooking characteristics, texture profile, and sensory traits of the tambaqui mechanically separated meat (MSM) and okara were analysed. Tambaqui MSM contained 78.18% moisture, 4.92% ash, 2.98% lipids, 12.47% protein, 1.45% carbohydrates, and 412.09 kcal energy/100 g. Okara contained 80.19% moisture, 3.48% ash, 3.90% lipids, 4.32% protein, 8.11% carbohydrates, and 417.00 kcal energy/100 g. The tambaqui MSM contained <10 most probable number (MPN)/g total and thermotolerant coliforms, and no E. coli or coagulase-positive staphylococci. The fresh okara contained 3.3 × 103 colony-forming units (CFU)/g facultative aerobic mesophiles, <10 CFU/g psychrotrophic bacteria when incubated at 7 °C for 7 days, 2.6 × 103 CFU/g moulds and yeasts, <10 MPN/g total and thermotolerant coliforms, and no E. coli. The intention to buy indicated that the tasters would buy the okara-enriched tambaqui fish burgers, and the fish burgers had good sensory acceptability, while the okara added nutritional value to the product. These results provide a promising option for making burgers using functional ingredients from by-products, as well as for adding value to the soy production chain by reducing waste.

(Submitted 21 June 2024; Accepted 17 September 2025; Published 30 December 2025)