Gamma irradiation of alkali extracted protein isolate from dephenolized sunflower meal

- Gamma irradiation increased the surface hydrophobicity of protein isolates.
- Particle size of protein isolates was increased after gamma irradiation.
- Antioxidant capacity of protein isolates was improved after gamma irradiation.
- Gamma irradiated protein isolates possessed better functional properties.

The effect of gamma irradiation on physicochemical, antioxidant and functional properties of sunflower protein isolates was investigated. Protein isolates were irradiated at dose level of 0, 10 20, 30, 40 and 50 kGy. Protein solutions obtained from irradiated protein isolates were found more turbid and had higher particle size. Surface hydrophobicity was increased while sulfhydryl content was reduced indicating the conformational changes in protein isolates. Surface hydrophobicity was increased from 122.73 to 139.67 and free sulfhydryl content was decreased from 7.60 to 7.22 μmoL/g and total sulfhydryl content from 78.79 to 52.26 μmoL/g. Available lysine content decreased from 3.30 to 3.21 g/100 g. Lightness of protein isolates was reduced with increase in yellow-brown colour indicating the formation of Maillard reaction products. DPPH radical scavenging of protein isolates was increased from 5.79 to 19.46% and total antioxidant capacity was increased from 7.54 to 27.50%. Solubility, oil binding capacity, emulsion properties and foaming properties were improved, while water binding capacity was impaired. Gamma irradiation treatment can be used to change the conformation of proteins, which could improve their functionality and widen the application area in food systems.