Drying method matters: differential preservation of lipids, pigments, and carbohydrates in edible macroalgae Fucus vesiculosus, Gracilaria sp., and Ulva sp.

Marine macroalgae are increasingly recognized as sustainable sources for food, feed, and functional applications. Drying is widely used to stabilize biomass and preserve nutrients and bioactive compounds. Freeze-drying (FD) effectively preserves sensitive compounds, but high cost and energy demand limit scalability. Therefore, this study evaluated air-tunnel drying (ATD; 25 °C) and solar drying (SD; 40 °C) as alternative methods for preserving lipid, fatty acid (FA), pigment, and carbohydrate composition of edible Fucus vesiculosus, Gracilaria sp., and Ulva sp., using FD as a reference. In most cases, ATD preserved lipid and carbohydrate contents comparable to FD. In Ulva sp., ATD promoted hydrolytic FA release, increasing free FA, while ulvan polysaccharides remained stable across drying methods. F. vesiculosus exhibited high stability, maintaining lipid content, FA composition, and pigment levels under all conditions. SD induced species-dependent alterations, including reductions in lipid content, polyunsaturated FA, and pigment levels in Gracilaria sp. and Ulva sp. Although F. vesiculosus polysaccharides remained largely unchanged, a potential increase in fucoidans was observed under SD, suggesting a stress-induced response. SD also decreased galactose and sulphate esters contents in Gracilaria sp. These findings support the selection of drying strategies according to species, target compounds and applications to optimize biomass quality.