Dehydration, Rehydration and Thermal Treatment: Effect on Bioactive Compounds of Red Seaweeds Porphyra umbilicalis and Porphyra linearis .

The nutritional and bioactive value of seaweeds is widely recognized, making them a valuable food source. To use seaweeds as food, drying and thermal treatments are required, but these treatments may have a negative impact on valuable bioactive compounds. In this study, the effects of dehydration, rehydration, and thermal treatment on the bioactive compounds (carotenoids, phycobiliproteins, total phenolic content (TPC), total flavonoids content (TFC)), antioxidant (ABTS and DPPH radical scavenging activities) and anti-Alzheimer's (Acetylcholinesterase (AchE) inhibitory activities, and color properties of Porphyra umbilicalis and Porphyra linearis seaweeds were evaluated. The results revealed significant reductions in carotenoids, TPC, TFC, and antioxidant activities after the seaweeds' processing, with differences observed between species. Thermal treatment led to the most pronounced reductions in bioactive compound contents and antioxidant activity. AchE inhibitory activity remained relatively high in all samples, with P. umbilicalis showing higher activity than P. linearis. Changes in color (ΔE) were significant after seaweeds' dehydration, rehydration and thermal treatment, especially in P. umbilicalis. Overall, optimizing processing methods is crucial for preserving the bioactive compounds and biological activities of seaweeds, thus maximizing their potential as sustainable and nutritious food sources or as nutraceutical ingredients.