Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Choose an application

• Reference Manager
• EndNote
• RefWorks (Direct export to RefWorks)

Today, healthy food has become increasingly important for people all over the world. In western countries, people have to deal more and more with so-called lifestyle diseases, such as diabetes and heart diseases, mainly caused by a poor diet, the use of tobacco and the lack of physical activity. Long chain &#969;-3 polyunsaturated fatty acids, especially eicosapentaenoic acid (EPA, C20:5&#969;-3) and docosahexaenoic acid (DHA, C22:6&#969;-3), are considered as essential fatty acids in a healthy diet, although their recommended daily intake is not reached by many people. Furthermore, fish stocks, which are not adequate to provide EPA and DHA to all people worldwide anyhow, are further declining. New sources of &#969;-3 LC-PUFA must thus be found. Since photoautotrophic microalgae are the primary producers of &#969;-3 LC-PUFA, they have been proposed as an alternative for fish. They are known to produce biomass through photosynthesis in a more efficient way than land plants, achieving a higher biomass productivity compared to traditional crops.In this context, the present study aimed to evaluate the potential of photoautotrophic microalgae as a source of &#969;-3 LC-PUFA rich oils as an alternative for fish oil. To do so, it was researched whether microalgae oils contain sufficient &#969;-3 LC-PUFA, whether some compounds (e.g. polar lipids, carotenoids and phytosterols) could add value to the microalgae oils and if they were stable. Furthermore, the methodology for food grade extraction of oils from photoautotrophic microalgae was also investigated. This study showed, in a first chapter, that microalgal biomass, especially in the form of a wet paste, was highly susceptible to hydrolysis. Freeze- and spray-drying were good drying methods, slowing down hydrolysis, although loss of certain interesting compounds, such as carotenoids occurred. Once properly dried and stored, chloroform/methanol 1:1 was shown to be the preferred solvent mixture for the analytical determination of total lipids from microalgae. Pretreatments, such as addition of isopropanol to inactivate lipases, addition of antioxidants or cell disruption were not necessary with this solvent mixture. In general, two extractions must be performed in series to safely compare lipid compounds between species. The total lipid extracts of the following microalgae were shown to be the most interesting: Isochrysis galbana (for DHA), Nannochloropsis gaditana, N. oculata and Phaeodactylum tricornutum (for EPA), and Pavlova lutheri and Thalassiosira pseudonana (for EPA and DHA). The necessary daily amount of the microalgal total lipid extracts to reach an EPA + DHA intake of 250 mg/day was reasonably low (< 2.5 g/day) for these microalgae species, except for Isochrysis (5 g/day). For comparison, a consumption of < 1 g/day of fish oil is required to reach the same &#969;-3 LC-PUFA intake. A largeproportion of the &#969;-3 LC-PUFA were present in the glyco- and phospholipid fraction of the oils, which can lead to a more efficient absorption and a better protection of EPA and DHA against oxidation.The amount of carotenoids in the microalgae oils was shown to be significant. They can guard the oil against lipid oxidation, lower oxidative stress in humans and provide other nutritionally beneficial properties. Nevertheless, total lipid extracts will never be used for human nutrition. Some solvent (mixtures) allowed in the food industry were however proven to be capable to extract the interesting lipids from the chosen microalgae, although without halogenated solvents only 50 to 75% of the present lipids and &#969;-3 LC-PUFA could be recovered. It was shown that hexane/isopropanol (3:2) gave markedly higher yields than the classic hexane extraction and that recovery was different for different microalgae species. Recovery of lipid components was generally in line with the permeability of the cell wall of the microalgae species, although other factors such as the localization - free or complexed to proteins or membranes - and the polarity of the lipid compound, may also play a role.Importantly, it was also found that the lipid extracts obtained with the food grade solvent (mixtures) contained a quite similar &#969;-3 LC-PUFA content as the total lipid extract, which means that the amount of microalgal oil to reach an EPA + DHA intake of 250 mg/day was in the same range as for the total lipid extracts, and thus feasible. Because of the higher absorption and oxidative stability of polar lipids, the hexane/isopropanol oil seemed to be more interesting than the hexane oil, since the former was not enriched in neutral lipids compared to the total lipid, while the hexane extract was. The amount of carotenoids in these oils was also significant, although for some even too high contents were recovered for potential human consumption. Furthermore, it was also shown that the microalgal oils were more oxidative stable than fish oil and heterotrophic microalgae oil. The hexane/isopropanol oils were even more stable than krill oil, while most hexane oils were not. While hydrolysis showed to be an important problem in the microalgal biomass, it was shown not to be an issue during the storage of oils.