Effects of Different Concentrations of Carrageenan on the Gel Properties and Structure of Hemp Protein Isolate

To elucidate the influence of different concentrations of carrageenan (CA, 0.4%, 0.8%, 1.2%, 1.6%, 2.0%, w/w) on the gelation properties and structure of hemp protein isolate (HPI), with the hemp protein isolate without adding CA as the control, the water-holding capacity, texture, rheological properties of the composite gels were determined. Meanwhile, the effect of CA addition on the water distribution, protein structure and intermolecular forces in the composite gels was also investigated. The results showed that the addition of CA significantly (P<0.05) improved the water-holding capacity and gel strength, and changed the protein structure. Compared to the control group, adding 0.8% CA significantly increased the hardness, elastic modulus and reduced the frequency dependence of the gel compared to the control group (P<0.05). And most tightly bound to water molecules, with a shift from α-helix to β-sheet and random curling, increasing the rigid structure of the gel. At this time, the primary force maintaining the gel structure shifted from hydrophobic interaction force to disulfide bonding and the gel network became denser, which was proved by scanning electron microscopy results. Therefore, the addition of 0.8% carrageenan could significantly (P<0.05) improve the gel properties and structure of hemp isolate protein, which would provide a theoretical and experimental foundation for the application of hemp protein isolate in the food industry (P<0.05).