Atmospheric cold plasma treatment of peanut protein: Structural and functional modifications accompanied by microbial reduction

Peanut protein serves as a substitute for animal protein, characterized by low levels of anti-nutritional factors and high protein content. However, poor solubility and emulsifying properties of peanut protein restrict its commercial applications. This study utilized atmospheric cold plasma (ACP) to treat peanut protein concentrate (PPC), aiming to improve its structural and functional properties. PPC samples treated with ACP for 0–150 s were subjected to a series of characterization methods. Electron paramagnetic resonance (EPR) confirmed the generation of reactive oxygen species during treatment, with hydroxyl radicals (·OH) identified as the primary drivers of protein oxidation and structural remodeling. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed a shift in secondary structure from alpha helix to beta sheet, reflecting conformational relaxation. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) further demonstrated progressive surface densification, reduced roughness, and increased porosity, indicating that aggregate dissociation was most evident at 90 s. These structural modifications were accompanied by enhanced surface hydrophobicity, a 42 % increase in solubility, and notable improvements in emulsifying activity, indicating that ACP treatment promotes favorable interfacial behavior and improved functional properties of PPC. This study demonstrated that ACP treatment induced structural modifications, including secondary structure transitions and aggregation changes, while enhancing the functional properties of PPC such as solubility, emulsification, and antibacterial activity. Comprehensive spectroscopic, physicochemical, morphological, and microbiological analyses provided deeper insights into the structure–function relationships of plasma-treated PPC.