Effect of drying techniques on color and bioactive potential of two commercial edible Indonesian seaweed cultivars

Seaweeds (Kappaphycus alvarezii and Sargassum duplicatum) are potentially rich sources of bioactive compounds and functional constituents that are used in food applications. Sun, oven, vacuum, and freeze-drying techniques are commonly used seaweed drying techniques and could be classified as cheap (sun and oven) and expensive (vacuum and freeze) drying techniques based on ovens’ market price. Therefore, the study was designed to investigate the effect of cheap (sun and oven) and expensive (vacuum and freeze) drying techniques based on color and antioxidant potential of K. alvarezii and S. duplicatum using phenolic and antioxidant assays. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to discriminate the drying techniques by instrumental color analysis. The results revealed that oven-dried seaweed extracts exhibited higher levels of phenolic (0.30 to 0.36 mg GAE g⁻¹) and antioxidant potential (3.59 to 79.68%). PCA and HCA discriminated the drying techniques into two well-defined groups/clusters I (oven, vacuum, and freeze-drying) and II (sun drying) and revealed higher ΔE values of sun-dried seaweed samples, which was interpreted as color was preserved using drying techniques of cluster I. Overall, oven, vacuum, and freeze-drying techniques reported similarities in color characteristics and could be an alternate drying technique to preserve the color of seaweed cultivars. Therefore, oven drying technique is recommended due to low cost (compared with vacuum and freeze-drying) and an affordable alternative to sun drying, the preferred technique in fishing communities of low-and-middle-income countries, for the development of seaweed-enriched functional foods.