Effects of dielectric barrier discharge cold plasma treatment on solubility and water holding capacity of peanut protein

The peanut protein, a protein-rich byproduct from oil extraction, contains 47%-55% high-quality protein, with low levels of anti-nutritional factors. It exhibits an excellent amino acid profile, a captivating aroma, and an exhilarating white color and is used as cholesterol-free commercial animal protein substitutes. However, its poor functional properties such as low solubility as well as emulsifying, foaming, and gel properties limit its applications. Therefore, improvement in the functional properties of peanut protein may be crucial to increase its application in food industry. Application of cold plasma (CP), a brand-new, nonhazardous and nonthermal, high technology with bright prospects, is currently attracting much attention. CP comprises ultraviolet photons, electrons, positive and negative ions, free radicals, and excited or non-excited molecules and atoms. In combination, these particles can break covalent bonds and initiate various chemical reactions. CP has been widely applied to clean, sterilize, and modify surfaces. Due to the advantages on broadness in frequency range, availability of the high-density non-equilibrium plasma in the larger space, simplicity in process, rapidity, efficiency, as well as other characteristics including energy-saving and environmental friendly, dielectric barrier discharge (DBD) cold plasma is considered to be the most popular plasma technology that can be applied in industry, thus becomes a major concern in the research field in modification of protein. Peanut protein solutions were modified by dielectric barrier discharge (DBD) cold plasma (CP) treatment. Effects of CP treatment on the structure and functional properties of peanut protein were evaluated by analysis of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared (FTIR) and protein surface hydrophobicity index (Ho). A significant improvement in solubility and water holding capacity was found to be improved by CP, and reached a maximum value at 2 min treatment, solubility of peanut protein reaches 132.78 mg/L and water holding capacity of peanut protein is 1.93 g/g, increasing by 24.8% and 79.6% respectively compared with untreated samples. At the same time, emulsion ability, emulsion stability, foaming ability, foaming stability and oil absorbing capacity was all improved to some extent after CP treatment. The results showed that the molecular weight of peanut protein remained unaffected, meanwhile, an increase in the β-sheet and random coil content and a decrease in the α-helix and β-turn content was found, indicating that the structure of the protein changed from compact to loosen after CP treatment. The results of surface hydrophobicity indicated that CP treatment induced tertiary structural changes of the proteins, Ho of peanut protein was increased remarkably. Our study results will further broaden the application of peanut protein in food industry such as dairy, meat products, and beverages. Furthermore, the operation was easy and the treatment time was short, which may make CP as a novel effective technology for protein modification.