Comparison of ultrafiltration-diafiltration and isoelectric precipitation for producing albumin and globulin fractions from hemp (Cannabis sativa L.)

This study aimed to compare the effectiveness of ultrafiltration-diafiltration (UF-DF) and isoelectric precipitation (IEP) for producing albumin (Alb) and globulin (Glo) fractions from hemp protein isolate (HPI), and to compare their structural and surface properties as well as solubilities. Compared to the Alb-IEP, the Alb-UFDF exhibited higher protein content (88.25 vs 73.76%), greater surface hydrophobicity (48.94 × 10 3 vs 38.80 × 10 3 a.u.), higher free sulfhydryl groups (25.12 vs 14.78 μmol/g), a more negative ζ-potential (−22.36 vs −10.06 mV), and higher α-helix content (9.03 vs 2.99%), indicating a better-preserved conformational structure. This structural integrity resulted in higher solubility for the Alb-UFDF compared to the Alb-IEP, although both albumin fractions remained highly soluble across all pH values. Protein profiles showed a slight contamination of the Alb-UFDF with 7S globulin. Both UFDF and IEP globulin fractions exhibited similar protein content (∼81%) and ζ-potential (∼−8 mV), but the Glo-UFDF showed higher free sulfhydryl content (27.90 vs 18.41 μmol/g) and surface hydrophobicity (100.22 × 10 3 vs 16.21 × 10 3 a.u.), indicating more pronounced denaturation for the Glo-IEP. Moreover, the solubility of the Glo-IEP was lower, particularly at pH 8 (18.31 vs 59.09%). Overall, UF-DF better preserved the conformation and solubility of hemp albumins and globulins compared to IEP, however the lower recovery yields indicate that further process optimization is required. Future work should assess the techno-functional properties of these fractions to evaluate their potential applications in food systems.