Investigating the effect of post-harvest treatment on nutritional and antioxidant activities of Ulva lactuca originating from Bangladesh

Abstract To utilise seaweed commercially, post-harvest processing is typically essential, serving to prevent decay, extend shelf life, and facilitate the extraction of specific chemical components. In this study, the presence of a variety of nutritionally important compounds in Ulva lactuca was investigated following different treatments: washing with fresh water (fresh), followed by drying under freeze dryer, open air, direct sun and conventional oven. The analysis encompassed the determination of proximate composition (carbohydrates, proteins, lipids, ash, and moisture), elements (C, H, N, S and P) and metal contents, bioactive compounds (phenolics and flavonoids), and in vitro antioxidant activities. The findings indicate that U. lactuca is rich in essential minerals, and total carbohydrate content is not significantly influenced by post-harvest drying treatments. Sun-dried U. lactuca exhibited the highest lipid (5.71 ± 0.41 % DW), phenolic content (52.9 ± 0.33 mg GAE g -1 DW), and total antioxidant capacity (16.19 ± 1.09 mg AAE g -1 DW), while air-dried only preserved the highest FRAP activity (0.38 ± 0.04 mg Fe 2 ⁺E g -1 DW) and DPPH scavenging (0.25 ± 0.03 mg AAE g -1 DW). Freeze-dried samples retained the highest protein content (9.69 ± 0.27 % DW) and reducing power (1.59 ± 0.05 mg AAE g -1 DW), whereas total flavonoids were greatest in the fresh sample (9.58 ± 0.08 mg QCE g -1 DW). Overall, sun or air drying are indicated as effective, low-cost methods for preserving the nutritional and bioactive qualities of U. lactuca compared to freeze or oven drying.