We used response surface methodology to investigate the effect of time and temperature of hydrothermal processing (blanching) on the phytochemical content, texture and colour of a semi-dried brown seaweed (Himanthalia elongata). A central composite design was employed with a hydrothermal processing time of 10–30 min and temperature of 60–90°C. Predicted models were found to be significant for total phenolic content, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, total flavonoids, total condensed tannins, texture and colour. The predicted values for each of the responses were in good agreement with experimental values. Processing time had the most significant effect on phytochemical constituents of H. elongata. An acceptable edible texture and colour of seaweed was also achieved during the blanching procedure. Thus, central composite design and response surface methodology can be used to model phytochemical content, texture and colour of H. elongata while minimising the number of experiments required. Multiple response optimisation demonstrated that the phytochemical content of H. elongata may be maximised by blanching for 20.4 min at 80.5°C.
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