Effect of gamma irradiation on structural, molecular, thermal and rheological properties of sunflower protein isolate

Protein isolates were prepared from sunflower meal using alkaline extraction technique and were irradiated at different doses (0, 10, 20, 30, 40 and 50 kGy). Sunflower protein isolates were evaluated for structural, molecular, thermal and rheological properties. Secondary structure of proteins was disrupted with decrease in α-helix content and concomitant increase in β-sheet content. The change in fluorescence spectra was observed indicating the alteration in tertiary structure of protein molecules mainly due to the conformational changes especially aggregation and crosslinking of protein molecules. Increase in thermal stability of protein after irradiation was found as determined by differential scanning calorimetry and thermal gravimetric analysis. Molecular weight of protein was increased in a dose dependent manner due to protein-protein crosslinking. Development of cracks on the surface of protein particle after irradiation was observed by scanning electron microscopy. Storage (G′) and loss modulus (G″) of protein dispersion was increased after gamma irradiation.