Effect of different drying temperatures on the moisture and phytochemical constituents of edible Irish brown seaweed

The effect of different temperatures on the drying kinetics and the phytochemical constituents of edible Irish brown seaweed, Himanthalia elongata were studied. This kinetic study involved the modelling of the terms of Fick's diffusion equation, for estimation of the diffusion coefficients. The diffusivity coefficient increased from 5.6×10^-07 to 12.2×10^-07m²/s as the drying temperatures increased with an estimated activation energy of 37.2kJ/mol. The experimental data was also fitted to different empirical kinetic models, Newton, Logarithmic and Henderson-Pabis, and the goodness of fit for the different models was evaluated. The effect of drying temperatures on the phytochemical constituents in seaweed was also evaluated. Drying at 25°C resulted in 49% and 51% reduction in the total phenol and total flavonoid content, respectively, as compared to fresh seaweed. However, the reduction declined as the drying temperatures were increased. The scavenging effect on DPPH radical was also greater for the fresh seaweed as compared to the dried form. An increase in the phytochemical content was seen for higher temperatures (35°C and 40°C) when the moisture content reduced by 50% indicating that this semi-dry state is even more nutritious than the fresh form and could be an interesting starting point for seaweed processing.