Effect of hydrothermal processing on colour, antioxidant and free radical scavenging capacities of edible Irish brown seaweeds

The effect of heat processing on change in colour (δE), level of bioactive compounds and overall antioxidant capacity in raw and heat-processed edible Irish brown seaweeds was investigated. Raw seaweeds were heated at 85-121 °C for 15 min in an autoclave and extracted with 60% methanol. In comparison with raw seaweeds for all the species studied, heating increased total phenol (TPC) (1.6- to 1.9-fold) and total tannin (TTC) (1.3- to 2.6-fold) at 95 °C, while total flavonoid (TFC) (1.6- to 3.3-fold) and total sugar (TSC) (1.9- to 4.3-fold) at 85 °C. Similarly, EC₅₀ value reduced in case of DPPH^• scavenging (30.7-51.8%), metal chelating ability (FIC) (27-67.8%) and H₂O₂ scavenging capacity (13.3-16.1%) at 95 °C, while reduction in lipid peroxidation (10.8-31.5%) observed at 85 °C. Results showed that heating affects content of bioactive compounds as well as beneficial biological activity associated with these compounds, which can suggest new processing for application of seaweeds extract as nutraceutical.