Development of an Aqueous Polyethylene Glycol-Based Extraction and Recovery Method for Almond (Prunus armeniaca L.) Protein

A novel method for protein extraction from sweet almonds with aqueous polyethylene glycol (PEG) as solvent and recovery from the extraction solution was developed. The extraction yields of different solvents, such as sodium hydroxide, sodium chloride, PEG 200, PEG 400, and PEG 600 aqueous solutions, were investigated and PEG 200 showed the highest extraction efficiency. The PEG-based microwave-assisted extraction (MAE) parameters were then optimized using response surface methodology. Under optimum condition, PEG 200 concentration of 25 % (w/w), liquid to solid ratio of 22 mL g(-1), microwave power of 120 W, extraction temperature of 45 A degrees C, and extraction time of 4 min, the average extraction yield was 93.75 +/- 3.15 %. Subsequently, the almond protein was recovered from the extraction solution containing PEG with an isoelectric point-ethanol synergy precipitation protocol. The combined technique integrated the speed of isoelectric point precipitation with the completeness of alcohol precipitation. The recovery of almond protein was 98.81 % with a time of 3-5 min. The proposed PEG-based MAE and synergy precipitation protocol provide a rapid and effective method for almond protein extraction and recovery and have the potential to be used for other plant proteins.