Physicochemical characterization and proximate composition of fermented yogurt enriched with lyophilized tambaqui (Colossoma macropomum) protein hydrolysate

Introduction: The valorization of fish processing byproducts as high-value protein ingredients has gained attention due to their nutritional density and techno-functional potential. Enzymatic hydrolysis produces low–molecular weight peptides with enhanced solubility, digestibility, and interfacial properties, enabling their incorporation into structured food matrices. Objective: This study evaluated the effect of incorporating lyophilized Tambaqui (Colossoma macropomum) protein hydrolysate on the proximate composition and physicochemical properties of fermented yogurt. Methodology: A completely randomized design was applied with two formulations: control (0%) and yogurt containing 3% (w/w) hydrolysate, produced in triplicate. Milk was heat-treated (90 °C/10 min) to enhance protein interactions, cooled to 42 °C, and inoculated with a thermophilic starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) at 3% (w/v). Fermentation occurred at 42 °C for 12 h. Analyses included proximate composition, pH, total solids, syneresis, and CIELAB color. Data were evaluated by ANOVA (p < 0.05). Results: Hydrolysate addition significantly increased protein content (4.69% to 9.46%), confirming effective enrichment, while carbohydrates decreased (6.83% to 1.92%). No significant changes were observed for moisture, lipids, ash, total solids, or syneresis, indicating preservation of structural stability. The enriched yogurt showed higher pH (5.76 vs. 5.49), suggesting modulation of acidification. Color parameters (L*, a*, b*) remained unchanged. Discussion: The marked protein increase demonstrates the efficiency of hydrolysate incorporation. The maintenance of syneresis indicates that peptide addition did not disrupt the casein network or water-holding capacity. The higher pH may be attributed to buffering effects of peptides, affecting acidification dynamics. The stability of color suggests minimal impact on visual attributes. Conclusion: The incorporation of 3% lyophilized Tambaqui protein hydrolysate enhances protein content while preserving the physicochemical properties of fermented yogurt, supporting its use as a functional ingredient in dairy products.