Impact of Ultra-High Pressure Assisted Alkaline Extraction on Properties and Structural Characteristics of Carrageenan

This study investigated the effects of ultra-high pressure (UHP)-assisted alkaline extraction on the physicochemical and structural properties of carrageenan. UHP treatment between 100 and 300 MPa significantly enhanced performance, with yield increasing by 12.7% at 100 MPa and gel strength reaching 911.57 g/cm 2 at 300 MPa, accompanied with a 16.15% improvement when compared with the control. Compositional analysis showed a 13.26% reduction in sulfate groups and a 19.63% increase in 3,6-anhydrogalactose at 300 MPa, together with higher uronic acid (increased by 30.11%) and total sugar (increased by 13.90%) contents. These changes resulted in functional improvements, e.g., the elevated water-holding capacity. LF-NMR analysis indicated the reduced water mobility and a higher proportion of bound water for carrageenan treated at 300 MPa. Antioxidant assays further confirmed that carrageenan treated at 300 MPa exhibited stronger radical scavenging activity, with DPPH and •OH clearance rates increased by 20.99% and 8.87% ( p < 0.05), respectively, whereas treatment at 500 MPa attenuated these effects. Overall, the results demonstrated that moderate UHP treatment, particularly at 300 MPa, effectively improved the structural and functional properties of carrageenan, supporting its potential application as a functional hydrocolloid.