Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond three atoms away from the terminal methyl group in their chemical structure. Fish is especially rich in the important omega -3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA plays a key role in many biological processes in the human body and are thus essential for human well-being. An Omega-3 process begins with high-quality, human-grade crude oil. In AQUABIOPRO-FIT, fish oil-based omega-3 oil concentrates are being developed by the partner Pelagia and the group company EPAX.

Pelagia Food is engaged in landing, refining and sales of pelagic fish for human consumption. The company has 14 production facilities in Norway, from Honningsvåg in the north to Egersund in the south, a refining and marinating facility in Skagen, Denmark, and owns 77% of a production facility in Shetland. Pelagia Feed’s core business is production of fishmeal, protein concentrates, fish oils, and omega-3concentrates in Norway, UK and Ireland. Pelagia feed have eight production facilities for fishmeal and fish oil, three facilities for production of oil and protein concentrate along with one Omega-3 concentrate production unit as EPAX. Pelagia has significant storage facility in Egersund, approved as a border station for import of protein and oils from third world countries.

Pelagia receives raw materials directly from fishing vessels landed and pumped into the production facility. The species is reliant on the seasonal catch, including mackerel, blue whiting, herring and capelin. Rest raw materials from whitefish are directly taken from fishing vessels whereas that of mackerel is being transported from Pelagia’s own filleting units immediately to the feed processing units for production of fish meal, fish oil and proteins. The average raw material intake at different facilities are in Table 1.

After refining the oil, effective purification process is applied to remove environmental pollutants. EPAX’s chosen method of production is molecular distillation, a tool specially developed for concentrating heat sensitive compounds such as Omega-3 fatty acids. The process is characterised by short-term exposure to high temperatures, and high vacuum in the apparatus, resulting in low thermal load on the oil. This means that the oils EPAX delivers have low concentrations of trans fatty acids and oligomers/polymers. Using molecular distillation as the starting point, EPAX can produce up to 800 mg/g EPA+DHA as a 90% triglyceride oil.

The quality of the oil depends on handling of the residual raw material received. The challenges associated with pelagic raw materials are that the quality changes happen quickly, and that the side-streams must be processed as quickly as possible after filleting in order to minimize oxidation during production. The rest raw materials contain high levels of blood and intestinal fractions of endogenous enzymes which may lead to enzymatic degradation and acceleration of oxidation. This in turn may lead to the formation of free fatty acids (FFA) and reduction in quality and stability of the oil.

In principle, two processes (thermal processing and enzymatic hydrolysis) can be used in the processing of residual raw material to oil and protein fractions. Thermal recovery of oil consists of grinding of the raw material, heating to the desired temperature and then separation of crude oil and protein phase (both soluble stick water and insoluble protein). The crude oil is taken for further polishing and refining. Enzymatic hydrolysis is a relatively low-temperature process where commercial enzymes are used for releasing of oil and breaking down of proteins and peptides followed by separation process. Because of the high degree of endogenous enzyme activity in the side-streams from pelagic species, like herring and mackerel, there is a challenge to find cost-effective process technology that will produce oil with low degree of oxidation and high stability as well as a satisfactory yield. Previous studies have shown that low extraction temperature gives a low oxidized oil whereas enzymatic process gives a higher yield of oil but at a cost of higher levels of oxidation and FFA. There is also a strategy to find solutions in between, including adding natural antioxidants to the raw material before processing.

The refining process includes following steps:

1. Molecular distillation (stripping) at high temperatures to remove environmental toxins as well as FFA.
2. Winterization is performed to make the oil clear at room temperature. This process removes wax and high melting point triacylglycerols, like stearin.
3. Bleaching is done to remove oxidation products and reduce the level of heavy metals and environmental toxins.
4. Deodorization and addition of antioxidant is carried out to remove odour and prevent oxidation of the oil.

Oils from North Atlantic pelagic species (herring and mackerel) contain a high proportion of monounsaturated long chain fatty acids (LC-MUFA) which is challenging for the traditional process steps used by Pelagia-EPAX. There is a need to reduce the amounts of MUFA, which is a modified processing step. One of the biggest challenges when concentrating on selected fatty acids is to separate the LC-MUFA and omega-3 fatty acids EPA and DHA. Crude oil produced from Norwegian pelagic raw material has unwanted fish smell and taste. So, an effective deodorization technology must be applied to reduce this sensory attribute.

For stabilisation of sensitive and perishable components present in the marine materials of our project we will consider using natural preservatives such as salt or sugar, and in some cases chemical (e.g. ethoxyquin, BHT, BHA) but preferably mostly natural antioxidants (tocopherols, rosemary extract, oregano extract, phenolic compounds, pigments etc.). The dosing of the different preservatives and antioxidant will be determined by use of accelerated oxidation test by Oxipres.

The induction periods (IP, hours) of the test materials containing perishable oils will be determined using an Oxipres apparatus (Mikrolab Aarhus, Denmark). The samples are weighed and introduced in the reaction glass containers and then inserted into the pressure vessels at room temperature. The vessels are then flushed with oxygen three times, and filled with oxygen (5.0, AGA AS, Norway) to a pressure of 5 bar and then inserted into a preheated heat block held at 90 °C. Data sampling of pressure in the vessels is taken at start and at 30 seconds’ intervals during the analysis. The induction period for each sample will be determined graphically from the intersection of two tangents to the pressure curve using Paralog Software Version 3.10, build 422 (Mikrolab Aarhus, Denmark).

Moisture content and water activity values of spray dried and freeze-dried saithe protein powders varied owing to the influence of additives and using different drying methods. Foods with aw values less than 0.3 are largely protected against lipid oxidation, non-enzymatic browning and enzymatic activity. Microorganisms also cannot grow under aw 0.6. Density of fish powder proteins also depends on particle size, ingredients and drying temperature.

Lipids can be isolated from fish side stream biomass by using solvent extraction methods (organic and/or supercritical CO₂) or separation technologies as described below. The raw material can be either homogenized or not prior to oil extraction. Homogenization can be realized for instance using high pressure or mechanical homogenizers and bead mills with or without following application of pulse fields.

Different lipid extraction methods are used depending on the raw material physicochemical properties as well as the final ingredient purpose. The results from lab or pilot scale extraction are transferable to variable degrees to large scale. The choice for the extraction method to be applied is usually based on the knowledge of existing possibilities of upscaling to a practical and economically viable degree. For laboratory scale oil extraction from smaller samples (e.g. 1-100 g) published methods are commonly used in which often multiple solvents (e.g. hexane, ethyl acetate and petroleum ether) are utilized:

As an example, in a recent study by Bogevik et al. (2018), the laboratory scale oil extraction from biomass of heterotrophically produced microalgae gave an oil yield of 63 and 65 % of the sample for Bligh & Dyer (1959) and Folch et al (1957) methods, respectively. On the other hand, up-scaled methods using only one solvent yielded significantly lower levels of oil (10, 14 and 19 % oil of the samples, with hexane, ethyl acetate and Soxhlet methods, respectively). Last, the super-critical CO₂ method extracted as low as 2 - 9 % oil from smaller samples, however without pre-grinding of the biomass.

These innovative extraction technologies (supercritical fluid extraction, ultrasound, Pulsed Electric Fields (PEF) and microwave-assisted extraction), also known as non-conventional methods, have been developed as alternatives to traditional methods, in full correspondence with green extraction concept for production of natural products. Non-conventional methods can be used for more effective separation and concentration of desirable compounds.

Several studies describe these techniques as methodologies that allows either avoiding or minimizing the use of organic solvents to extract high-added value compounds, along with other beneficial features including reduction of treatment time, intensification of mass transfer process, increasing the extraction yields, preserving high extract quality and reducing the energy consumption.

In addition, the extraction of high-added value compounds by means of most of these non-conventional technologies occurs at low and mild processing temperatures, which can preserve them from degradation, in contrast to conventional processing techniques when high temperatures are used.

Therefore, non-conventional technologies can be a complementary alternative to conventional processes in order to reduce the consumption of solvents which can be toxic, high temperatures and reduce the extraction time, thus decreasing the carbon footprint. They can even improve the efficiency of extraction and in the case of specific technologies such as pulsed electric fields can allow to selectively extract the targeted compounds thus decreasing the separation and purification stages.

1. Huda, N., Abdullah, R., Santana, P., Yang, T.A., 2012. Effect of different dryoprotectants on functional properties of threadfin bream surimi powder. J Fish Aqua Sci. 7, 9.
2. Shaviklo, G.R., Thorkelsson, G., Arason, S., Kristinsson, H.G., Sveinsdottir, K., 2010. The influence of additives and drying methods on quality attributes of fish protein powder made from saithe (Pollachius virens). Journal of the Science of Food and Agriculture 90, 2133-2143.