Effect of different drying methods on phytochemical content and amino acid and fatty acid profiles of the green seaweed, Ulva spp.

Green seaweeds are a potential source of proteins, minerals, fatty acids, and essential amino acids, and also often contain bioactive compounds with antioxidant activity. They have the potential to be a source of functional and nutraceutical ingredients. However, their elevated water content shortens shelf life; thus, a preservation method should be employed, such as drying. In the present article, Chilean green seaweed (Ulva spp.) was characterized and the effect of different drying methods (freeze-, vacuum-, solar-, and convective drying) on the quality of dried algae as functional ingredient, along with a description of the drying parameters for each method was evaluated. Proximate composition of fresh Ulva spp. indicated that, other than water, ash, protein, and crude fiber are the main constituents. Ulva samples also had a high amount of total dietary fiber (with an IFD/SFD ~ 1.5). The isotherm curve presented the typical type II sigmoid shape and the BET model gave the best fitting. There was a significant effect of drying method on proximate composition of dried Ulva and the convective drying the method that showed higher values for almost all parameters, except fat content. Color was not affected by drying and the typical green color was present in all samples. Total flavonoid content (TFC), total carotenoids and antioxidant capacity (DPPH and ORAC) were also higher in convective drying. In addition, other minor components with nutritional value were identified, such as essential polyunsaturated fatty acids (PUFAs with a ω3/ω6 ratio of 1:1) and amino acids. Among the different drying methods applied, convective drying (70 °C, 120 min) better retained the physicochemical parameters and antioxidant capacity of Ulva spp.