Effect of post-harvest processing on nutritional and antioxidant activities of Ulva sp. originating from Bangladesh

To optimize the utility of seaweeds, 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 sp. (grown locally in Bangladesh) was investigated following different treatments: washing with fresh water (fresh), followed by air drying and oven drying. The analysis encompassed the determination of proximate composition (carbohydrates, proteins, lipids, ash, and moisture), elements (C, H, N, S and P), minerals (K, Ca, Mg and Fe), potential bioactive compounds (phenolics, flavonoids, chlorophyll and carotenoids), and in vitro antioxidant activities. The findings indicated that fresh samples exhibited higher levels of nutrients, bioactive compounds, and antioxidant activities. The highest levels of primary metabolites [carbohydrates (50.03 ± 1.74%, DW), protein (11.02 ± 2.35%, DW), lipid (4.16 ± 0.07%,, DW)], pigments [chlorophyll (0.602 ± 0.012%, DW), carotenoid (0.057 ± 0.005%, DW)], moisture (90.28 ± 0.0%) and antioxidant activities [total antioxidant capacity (10.2 ± 0.20 mgAAE/g, DW), reducing power (0.26 ± 0.02 mgAAE/g, DW), ferric reducing antioxidant power (29.61 ± 2.02 mmol Fe ²⁺ /g, DW)] were observed in fresh samples. Air-dried and oven-dried samples showed no significant differences in concentrations of these phytochemicals and antioxidant activities except that phenolic and flavonoid contents. Ulva sp. also showed having a notable amount of certain elements [C (27.02 ± 2.01%), H (5.56 ± 0.38%), N (3.48 ± 0.19%), S (5.95 ± 0.32%) and P (0.91 ± 0.02%)] and minerals [K (0.67 ± 0.01%), Ca (0.94 ± 0.13%), Mg (0.59 ± 0.01%) and Fe (0.21 ± 0.01%)]. In conclusion, fresh Ulva sp. could be more preferable to retain nutritional qualities compared to an air-dried or oven-dried processed sample.