Optimization and characterization of hazelnut protein isolate gam arabic and sodium alginate conjugates

Plant-based proteins are gaining increasing attention due to their renewable nature, low cost, and environmental benefits. However, limitations in their functional properties restrict their application in the food industry. This thesis aims to evaluate the potential of hazelnut protein, a plant-based protein source, as an alternative to animal proteins in the food industry. Hazelnut protein isolate (HPI) was obtained from the by-product of hazelnut oil extraction using the cold press method. To enhance its functional properties, HPI was conjugated with sodium alginate (SA) and gum arabic (GA) polysaccharides using the wet-heating method under different temperature (60–90°C), time (3–12 hours), and protein-to-polysaccharide ratio conditions (25–75%). As a result of the conjugation process conducted under optimum conditions, the solubility of HPI increased from 15.23% to 52.12% in SA-HPI conjugates and 59.82% in GA-HPI conjugates. The emulsion activity of control HPI (7.11 m²/g) increased to 22.49 m²/g in GA-HPI and 31.55 m²/g in SA-HPI. Emulsion stability improved from 80.65% in control HPI to 104.4% in GA-HPI and 95.45% in SA-HPI conjugates. The highest glycation degree was observed in SA-HPI conjugates, reaching 20.16%. Viscosity values were found to be higher in GA-HPI conjugates. The anionic properties of SA reduced viscosity, whereas GA provided a more stable gel structure. Structural analyses showed an increase in β-sheet content and a decrease in α-helix content after conjugation. Compared to control HPI, L* (lightness) values increased in the conjugates, while a* (redness) and b* (yellowness) values decreased. The browning index of SA-HPI and GA-HPI conjugates was lower than that of control HPI. During glycation, the HMF content ranged between 4.86 mg/kg in GA-HPI and 3.56 mg/kg in SA-HPI. Zeta potential analysis indicated a decrease in GA-HPI compared to control HPI, signifying reduced electrostatic repulsion and increased aggregation. On the other hand, SA-HPI exhibited a more negative zeta potential than the control. In conclusion, the conjugation of HPI with SA and GA enhanced solubility, gel strength, and emulsion properties, demonstrating that these conjugates can be effectively utilized in the food industry.