Effect of cold plasma-activated water on the physicochemical and functional properties of Bambara groundnut globulin

Abstract

There is a growing interest in sustainable and green technology for the improvement of functional properties of grain proteins by altering their composition and structure. This study investigated the structure, physicochemical and functional properties of Bambara groundnut globulin after hydration with plasma-activated water (PAW). Bambara groundnut globulin was dispersed in PAW and hydrated at 4 ℃ for about 12 h. The exposure of Bambara groundnut globulin to plasma resulted in a significant loss of helical structure and over 3-fold increase in β-turns in comparison with the untreated Bambara groundnut protein. Amino acid data for the plasma-treated globulin showed 20 % reduction in glutamic acid content. A slight redshift was observed in fluorescence intensity data of the plasma-treated Bambara groundnut protein. This suggested an unfolding of the protein structure, which also correlated with the observed increased hydrophobicity. However, protein profiles by gel electrophoresis, surface charge, and pH-solubility patterns appeared similar for both plasma-treated and untreated Bambara groundnut globulin samples. Bambara groundnut globulin had reduced emulsifying ability after exposure to plasma as indicated by an increase in the average oil droplet sizes. However, foaming capacities were significantly better and stable at up to 15 mg protein/mL. The hydration of Bambara groundnut globulin with plasma-activated water modifies the structural conformation, reduces the proportion of acidic amino acids of the protein, and improves the foaming properties. Cold plasma treatment by hydration does not seem to improve the emulsifying properties of Bambara groundnut globulin.