Enzyme-Assisted Extraction and Hydrolysis of Dulse (Palmaria palmata) Proteins: Characterisation, Antioxidant Activity and Glucose-Management Potential

This study investigated the impact of temperature and enzyme-assisted extraction (EAE), specifically using carbohydrase, on protein recovery from Palmaria palmata. It also evaluated the antioxidant and glucose-management potential of enzymatic hydrolysates and simulated gastrointestinal digests (SGIDs) of selected protein extracts. Preincubation at 4 °C with xylanase- and cellulase-containing preparations achieved the highest protein and biomass recovery yields (75.1 ± 2.4% and 17.6 ± 0.6%, respectively). Protein extracts were hydrolysed using food-grade proteases and subsequently subjected to SGID. Both hydrolysates and SGID samples exhibited antioxidant activity, with SGID generally resulting in enhanced oxygen radical absorbance capacity (ORAC) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activities. Neutrase® hydrolysates had the highest dipeptidyl peptidase IV (DPP-IV) inhibitory activity, while similar IC50 values were observed within the SGID samples. All hydrolysate/SGID samples promoted insulin and active glucagon-like peptide-1 (GLP-1) secretion and inhibited DPP-IV activity in cell-based assays. These findings highlight the potential of P. palmata protein extract (PPPE) digests for antioxidant and glucose-management applications, supporting their potential utilisation as multifunctional food ingredients.