Objective Investigating the effects of cold plasma treatment for different durations on the protein structure and functional properties of peanut meal to lay the foundation for its high-value utilization.

Method Peanut meal protein was treated with cold plasma at a discharge voltage of 120 kV and discharge frequency of 50 Hz for 0, 1, 3, 5, 7, and 9 min, respectively. The solubility, foaming properties, water and oil holding capacities, emulsifying properties, and structural changes were systematically analyzed.

Result Cold plasma treatment significantly improved the functional properties of the peanut meal protein, exhibiting an initial enhancement followed by a decline with increasing treatment time. The solubility and surface hydrophobicity of peanut meal protein both peaked at a cold plasma treatment time of 3 min, with maximum values of 48.71% and 65.41, respectively. Foaming capacity and water-holding capacity reached their maxima at 5 min, corresponding to 195.56% and 2.17 g/g. Emulsifying activity and emulsifying stability attained optimal values at 1 min and 3 min, with peak levels of 9.70 m²/g and 24.82 min, respectively. With prolonged treatment duration, the particle size of peanut meal protein first increased and then decreased, reaching a maximum of 371.63 nm at 7 min. The absolute value of Zeta potential rose initially and declined afterwards, peaking at 21.37 mV at 3 min, which reflected a transformation process of protein depolymerization followed by aggregation.The contents of free sulfhydryl, carbonyl and dityrosine of peanut meal protein increased first and then decreased as treatment time extended. The free sulfhydryl content hit the highest level of 4.02 μmol/g at 3 min; the carbonyl content reached a maximum of 6.46 nmol/mg at 5 min; the dityrosine content peaked at 27 276.16 at 2 min. These results indicated intensified protein oxidation and cross-linking degree upon plasma treatment. Cold plasma treatment did not introduce new functional groups, yet it triggered rearrangement of protein secondary structure accompanied by elevated random coil proportion, resulting in a looser molecular conformation.

Conclusion Appropriate-duration cold plasma treatment can enhance the functional properties of peanut meal protein by promoting protein structural loosening and exposing active groups. In contrast, prolonged cold plasma treatment intensifies protein oxidation and increases structural compactness, which is detrimental to maintaining the functional properties of the protein.