Seaweed based antioxidants – analysis and application

The overall aim of this work was to develop novel seaweed based antioxidants. The objectives were to extract, identify and characterizing the phlorotannins from Nordic brown algae Fucus vesiculosus and furthermore evaluate F. vesiculosus extracts in different food and cosmetic o/w emulsions. Extracts from Icelandic F. vesiculosus were conducted using ethanol, acetone, ethyl acetate and water.

The antioxidant properties were evaluated in vitro by antioxidant assays. Furthermore, the extracts were characterized based on composition of bioactive compounds influencing the antioxidant activity. Application of the extracts was evaluated in facial cream (20ºC/dark or light, 40ºC/dark), 5% fish-oil-enriched milk (5ºC), mayonnaise (20ºC) and granola bars (20ºC).

Addition of fish oil increased lipid oxidation due to the high content of n-3 long chain polyunsaturated fatty acids (PUFA) in fish oil. Hence, if the antioxidants showed high effectiveness in these foods these could be suitable for any kind of lipid rich food with the same or lower amount of PUFAs.

The oxidative stability was evaluated over time by determining different oxidation parameters, such as primary and secondary oxidation products. Additionally, pressurized liquid extraction (PLE) was evaluated as potential “green” extraction method to extract phlorotannins from F. vesiculosus. PLE extracts were conducted from Danish F. vesiculosus.

The phenolic content and in vitro antioxidant properties were determined. The phlorotannins were identified and the antioxidant activity of specific compounds was determined using HPLC-DAD-ECD-DAD-qTOFMS. The results are not finalized. Results showed a large variety of bioactive compounds in the extracts both with potential antioxidant and/or prooxidant activity.

All extracts exhibited high radical scavenging activity (≈ 100%) and moderate metal chelating ability (20-60%). In food application, increased lag phase of secondary oxidation products related to oxidation of fish oil was observed when extracts were added. High phenolic content was related to a high antioxidant efficacy in foods.

In facial creams the extracts limited formation of pentanal during storage. Acetone extract was more efficient than water extract towards limiting formation of pentanal. Elevated temperatures caused unstable emulsions and syneresis. Furthermore, creams changed color from white to more red/brown at all storage conditions.