Behavioral Solubilization of Peanut Protein Isolate by Atmospheric Pressure Cold Plasma (ACP) Treatment

The solubilization of peanut protein isolate (PPI) powders modified by atmospheric pressure cold plasma (ACP) treatment was studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), low-field nuclear magnetic resonance (low-field NMR) spectroscopy, and FTIR spectroscopy. Significant improvements in both the solubility and water holding capacity (WHC) of the PPI gel were observed after treatment with ACP. The PPI solubility reached a maximum value after 7 min of treatment, with a 12.17% increase over the values observed for the untreated samples. In addition, the WHC increased by 17.90% after 3 min of treatment. The SEM and EDS data revealed that following the 7-min treatment, the PPI surface was rougher and more loosely bound than that of the untreated sample. This indicated an increase in the PPI specific surface area and exposed protein-water binding sites on the treated PPI surface as well as a marked increase in its oxygen content, suggesting an increase in the hydrophilic groups on the PPI surface. The low-filed NMR measurements revealed that the trend in the T-21 peak area of the relaxation time was consistent with the data observed for the WHC. The FTIR results revealed a decrease in the proportion of beta-sheets and an increase in that of the beta-turns within 3 min of treatment, suggesting that the polarity and hydrophilicity of the protein surface were enhanced. The protein structure changed from a compact folding to a loose unfolding configuration after ACP treatment.