Structural and Functional Modifications of Hazelnut Proteins Induced by Atmospheric Cold Plasma

This study evaluated the effects of atmospheric cold plasma (ACP) treatment duration on the physicochemical and functional properties of hazelnut protein. Proteins were extracted from defatted hazelnut flour and subjected to ACP for 0, 2, 4, 6, and 8 min. The results demonstrated that ACP treatment significantly modified protein characteristics: it generally reduced particle size and increased absolute zeta potential, with the smallest particles observed after 4 and 6 min of treatment. Concurrently, a decrease in L, a, and b color values indicated sample darkening with extended processing. Structural analysis revealed that ACP induced changes in protein secondary structure, leading to a significant increase in surface hydrophobicity and a decrease in free sulfhydryl content. These structural and physicochemical modifications, particularly the enhanced surface hydrophobicity and reduced particle size, collectively improved emulsifying activity and stability, as well as foaming capacity and stability. The highest emulsion and foaming stability were observed in samples treated for 6 min. Hazelnut protein gels exhibited pronounced solid-like behavior and ACP treatment enhanced the rheological properties of the gels, with the maximum gel strength observed at a 6 min treatment. Overall, these findings indicate that ACP is an effective non-thermal technology for positively altering the physicochemical and techno-functional properties of hazelnut protein.