Composition and functionalities of peanut protein concentrates using ethanol as a defatted solvent and a...

Defatted solids (DSs) from vegetable oil extraction represent valuable feedstocks for producing protein concentrates with tailored functional properties. In the present study, using peanut protein concentrates obtained from press cakes defatted with ethanol (DSEt) or hexane (DSHx), we aimed to evaluate ethanol as a green solvent for oil extraction and as a protein-precipitating agent. Protein extraction was optimized by assessing temperature and pH, and purification was performed using isoelectric (IP) or alcoholic (AP) precipitation.

Extractions at 75 °C and a pH of 9.0 resulted in higher protein extraction yields for DSEt (89 ± 3%) and DSHx (95 ± 1%). The protein contents reached 780 ± 30 g kg^-1 (IP) and 790 ± 10 g kg^-1 (AP) for DSEt and 730 ± 30 g kg^-1 (IP) and 750 ± 10 g kg^-1 (AP) for DSHx (dry basis). Both the solvents and the precipitation methods maintained the thermal stability of the proteins, although the denaturation enthalpies indicated that IP was less severe than AP. Compared with DSHx-IP (88 ± 4% and 43.0 ± 0.1%, respectively), the DSEt-AP proteins showed higher solubility (99.84 ± 0.01%), foam formation (71.0 ± 0.1%) and comparable emulsifying and water- and oil-absorption capacities. Fourier transform infrared spectroscopy indicated that the ethanol used in defatting altered the hydrophilic/hydrophobic balance, exposing more hydrophilic groups regardless of the precipitation method. AP reduced the protein hydrophobicity more strongly in DSHx solids, possibly because of depolymerization/aggregation of arachin subunits.

The use of ethanol in both the defatting and precipitation stages enables the production of protein concentrates with functional properties equivalent to those of conventional hexane-IP methods at the same time as using a greener, safer solvent. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.