Seasonal and spatial compositional variation of the red algae Mastocarpus stellatus from the Northern coast of Portugal

This study focusses on the valorization of the red seaweed Mastocarpus stellatus, collected in the Northern coast of Portugal, as a natural source of high value compounds due to its beneficial properties. An annual monitoring of the seaweed was performed by determining its lipids, ash, carbohydrates, phycobiliproteins, total phenolic compounds, antioxidant capacity and carrageenan from three different rocky shores located in the north of Portugal. The results showed a seasonal and spatial variability of the studied compounds between October 2018 and September 2019 depending on the climatic variables of temperature, precipitation, and solar radiation. The most productive season coincided with the warmest months, except for carbohydrates and phycobiliproteins, which were promoted in the colder season. The spatial variation also could be explained by the proximity to water channel discharges at the sampling sites. Complementary studies on the carrageenan fraction were conducted in one of the shores due to the high biopolymer content, to determine their carrageenan proportion between the summer and winter period and establish their rheological capabilities for the formulation of gelling matrices. The extracted biopolymers exhibited typical structural and viscoelastic characteristics of kappa/iota-hybrid carrageenans, suggesting notably differences depending on the harvest season, which is critically relevant to define future applications.