Deep eutectic solvents and alkaline extraction of protein from seabuckthorn seed meal: a comparison study

Seabuckthorn seed meal (SSM) is a waste of oil extraction industry that rich in protein. In order to seek suitable protein extraction method, three different deep eutectic solvents (DESs) (including choline chloride-glycerol, choline chloride-oxalic acid and choline chloride-urea) were developed for extracting protein from SSM and compared with alkaline. Result indicated that alkaline could effectively extract 56.9% protein from SSM and its protein content was 73.1%, higher than DES at 31.0%41.4% and 64.3%67.5%, respectively. However, compared to alkali, DES led to a product with less β-sheet, more β-turn, more essential amino acids, higher total amino acid content, especially choline chloride-urea which extracted protein showing an integrated and similar protein weight distribution compared to SSM. Also, this protein extracted chloride-urea showed a highest digestibility in vitro (by pepsin) (54.2%). These results indicated that choline chloride-urea extraction is better than alkaline extraction for SSM.