Integrated extraction, film formulation, and physicochemical comparison of crude carrageenans from Mastocarpus stellatus: Exploring enzymatic, hydrothermal, and ultrasonication pathways

Abstract This study evaluated various extraction pathways for crude carrageenan extraction (CCAR) from Mastocarpus stellatus (Stackhouse) Guiry, using combinations of hydrothermal-, enzymatic- (Cellic ® CTec3), and ultrasound (US)-assisted extractions. Extraction yield, purity, chemical composition, structural features, film and gel rheology were assessed to guide an integrated seaweed biorefinery design. Hydrothermal-assisted extraction yielded CCAR with a low ash content of 17% (d.w.) and an apparent molecular weight (M w ) of 1087 kDa, though recovery was limited (11.1%). Enzymatic extraction (CCAR-6) achieved the highest CCAR yield (38.5% d.w.) while maintaining relatively high M w (1210 kDa). Combined enzyme-US extractions resulted in CCAR recovery up to 33.5% d.w. but with increased ash and protein contents, especially in carrageenan recovered from solid residue extracts (e.g., CCAR-7: 35.5% ash, 6.1% protein; d.w.). Gels from CCAR with low contamination and high apparent M w , tended to higher complex viscosity. Conversely, gels derived from low M w or high-ash CCARs, showed lower complex viscosity. Rheological analysis of carrageenan films with PEG600 revealed correlations between extract purity, and viscoelastic performance, although no clear effect of M w could be distiguished. Overall, the results underscore the impact of different extraction technologies on CCAR functionality and purity, as well as potential of solid residues, providing a foundation for efficient and sustainable extraction protocols in macroalgal biorefineries.