Effect of drying on the production of fucoxanthin isomers from brown seaweeds

Fucoxanthin, an algal carotenoid with bioactivity that benefits human health, is gaining popularity as a functional food. Therefore, in this study, the effect of drying methods and conditions on the production of fucoxanthin isomers in three closely related Sargassum species with slightly different morphological lamina were investigated. The recovery of fucoxanthin after oven-drying was 1.1–1.3-fold higher than that after sun-drying and varied 1.6-fold among the S. species used, indicating that each algal species has a different heat susceptibility even among closely related species, and should be optimized for each species and drying method. In Padina australis with homogeneous morphology, the optimal temperature to maintain all-trans form was 60°C with only a 5.3% loss, while other cis-isomer transformations were maintained at 80°C. The apparent activation energy estimated by Arrhenius plots differed for the all-trans form and cis-isomer transformations, indicating the presence of different reactions between them. Practical applications Drying treatment is an efficient and cost-effective technique for reducing the moisture content of post-harvest seaweed to prevent decomposition, increase shelf life, and easily extract the targeted compounds. Owing to the difference in heat susceptibility, even in closely related species, the results indicated that it should be necessary not only to select appropriate algal species and drying methods but also to optimize the thermal conditions for each target substance of the selected material. This study provided qualitative information, particularly on seaweed drying procedures, and contributed to the production of marine products in the fields of food and bioactive substances, such as fucoxanthin isomers.