Exploring Alternative Red Seaweed Species for the Production of Agar-Based Hydrogels for Food Applications

Three different red seaweed species, Gelidium corneum and two Gracilaria species (Agarophyton chilensis, and Gracilariopsis longissima), were used to produce agar-based fractions through conventional and simplified extraction methods and their composition and gel-forming properties were evaluated. The use of an alkaline pretreatment was effective in removing impurities such as proteins, lipids, and ash, while the agarose/agaropectin ratio in agar was not affected. This led to the formation of hydrogels with higher stiffness and strength. Surprisingly, the presence of semi-crystalline agaropectin in the agar fractions from the two Gracilaria species, especially G. longissima, promoted the formation of more densely packed and stronger hydrogel networks, with higher gelling temperatures and superior mechanical properties. Thus, these results suggest that G. longissima has the potential to be used as an alternative to the more widespread use of G. corneum for the production of agar hydrogels for food applications.