Effect of Processing Conditions on Phytochemical Constituents of Edible Irish Seaweed Himanthalia Elongata

Seaweed is well recognized as an excellent source of phytochemicals. This study was a preliminary screening to investigate the effects of various food processing methods on the phytochemicals of Himanthalia elongata. Hydrothermal processing was carried out until an edible texture was achieved. The total phenolic content (TPC) of fresh H. elongata was 175.27 mg gallic acid equivalent (GAE)/100 g fresh weight (FW) while boiling significantly reduced the TPC to 25.4 mg GAE/100 g FW (P < 0.05). A drying pretreatment before boiling reduced the cooking time therefore leading to less leaching of antioxidants upon boiling. In terms of extract, drying of H. elongata followed by boiling had the most significant effect on the phytochemicals as TPC increased by 174%. Boiled extracts had the most effective 2, 2-diphenyl-1-picrylhydrazyl scavenging activity (EC50 of 12.5 µg/mL). As a comparison, seaweed subjected to the same treatments was studied in terms of antimicrobial activity. Overall, extracts from fresh H. elongata achieved the highest inhibition. PRACTICAL APPLICATIONS Seaweeds contain various phytochemicals with potential health benefits and hence have potential as functional ingredients. Processing of vegetables for consumption exposes the phytochemicals present to detrimental factors that may lead to alterations in concentrations and health-related quality. Because seaweeds are consumed after some form of processing, it is important to investigate the effect of such treatments on the bioactive compounds that are present. The effect of common processing conditions on the phytochemical constituents of an edible Irish seaweed, Himanthalia elongata, were investigated in terms of whole seaweed and as an extract. The nutritional quality of the samples varied with the different processing treatments. A drying pretreatment before boiling reduced the cooking time therefore leading to less leaching of antioxidants upon boiling. These findings are promising as such processing conditions could be applied in the development of new functional foods from whole H. elongata or its extracts.