Extraction of a Seaweed Lipid Fraction and Evaluation of its Ability to Prevent Lipid Peroxidation in Fish Oil
Examensarbete för masterexamen
Biotechnology (MPBIO), MSc
This project is a part of the Sweaweed project which aims to evaluate the use of the seaweed species Porphyra umbilicalis and Ulva lactuca grown along the west coast of Sweden, for high value products. This particular project evaluated the use of the seaweed as a source of long chained n-3 polyunsaturated fatty acids (LC n-3 PUFA), and as a source of natural antioxidants able to preserve other LC n-3 PUFA from oxidation. In a first part of the project, different extraction techniques (polytron, sonication and bead beating) were evaluated for their efficiency in extracting lipophilic compounds (carotenoids, chlorophyll and phenolic compounds) from seaweed into sunflower oil. In the second part, lipid oxidation in seaweed-fortified fish oil was studied during storage as well as during in vitro gastrointestinal digestion. By using a polytron, the highest amounts of carotenoids, chlorophyll and phenolic compounds were extracted from the seaweed into sunflower oil and fish oil. No fortification of LC n-3 PUFAs was however detected in the sunflower oil fortified with Porphyra umbilicalis or Ulva lactuca. The fish oil fortified with Porphyra umbilicalis experienced 29% less degradation of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) compared to pure fish oil during storage in room temperature and daylight for 28 days. The fish oil fortified with Ulva lactuca experienced 22% and 37% less degradation of EPA and DHA compared to pure fish oil. The amount of peroxides after 28 days of storage was 22% and 21% less in the fish oils fortified with Porphyra umbilicalis and Ulva lactuca. The amount of malondialdehyde (MDA) produced was 40% and 45% less in the fish oil fortified with Porphyra umbilicalis and 70% and 68% less in the fish oil fortified with Ulva lactuca after 7 and 28 days of storage compared to pure fish oil. The amount of 4-hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE) was higher in the fish oil fortified with Porphyra umbilicalis after 7 days, and higher in the fish oil fortified with Ulva lactuca after 28 days, when compared to pure fish oil. No significant difference was noticed regarding rancid odor in the different fish oils. The extracted seaweed compounds had no preserving effect against oxidation of fish oil during in vitro digestion. Altogether, the fortifying and stabilizing effects from extracting seaweed with food oils were lower than expected, which could be due e.g. to LC n-3 PUFA being firmly bound in lipid classes that are difficult to extract with such a hydrophobic media as oil. Also, simultaneous extraction of pro-oxidative trace elements with the antioxidants may have had a counteracting effect on the stability.
Biologiska vetenskaper , Biological Sciences