Genipin-Aided Protein Cross-linking to Modify Structural and Rheological Properties of Emulsion-Filled Hempseed Protein Hydrogels

Genipin, a natural electrophilic cross-linker, was applied (5, 10, 20, and 30 mM) to modify hempseed protein isolate (HPI). Genipin treatments resulted in general losses of total sulfhydryls (up to 2.9 nmol/mg) and free amines (up to 77.3 nmol/mg). Surface hydrophobicity decreased by nearly 90% with 30 mM genipin, corresponding to similar tryptophan fluorescence quenching. The genipin treatment converted HPI into highly cross-linked polymers. Hydrogels formed with such polymers when also incorporated with hemp oil emulsions exhibited substantially enhanced gelling ability: up to 3.3- and 2.6-fold increases, respectively, in gel strength and gel elasticity over genipin-untreated protein. The genipin-modified composite gels also exhibited superior water-holding capacity. Microstructural analysis revealed a compact gel network filled with protein-coated oil globules that interacted intimately with the protein matrix when treated with genipin. Such gels remained readily digestible. Hence, genipin-treated hemp protein hydrogels show promise as functional food components.