Effect of different rehydration temperatures on the moisture, content of phenolic compounds, antioxidant capacity and textural properties of edible Irish brown seaweed

The effect of temperature (20, 40, 60, 80 and 100 °C) on the rehydration kinetics and phytochemical constituents of dried edible Irish brown seaweed, Himanthalia elongata, were studied. The moisture content of fresh and dried seaweed was 4.07 and 0.07 g water/g dry basis, representing a 98.1% reduction in water content. All rehydration moisture curves had a clear exponential tendency, and it was observed that the rehydration time decreased when temperature was increased. Although restoration of the product to its original moisture content was achieved, rehydration resulted in losses in phytochemical content. Moisture equilibrium was achieved fastest at 100 °C (40 min) with losses of 83.2 and 93% in the total phenol and total flavonoid contents, respectively. The moisture content was fitted to empirical kinetic models; Weibull, Peleg's, first-order and exponential association. Activation energies of 4.03, 4.28 and 3.90 kJ/mol were obtained for the parameters of Peleg's, first-order and exponential models, respectively.