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Reporting period: 2015-08-24 to 2017-08-23

Functional foods containing omega-3 polyunsaturated fatty acids (PUFA) is one of the food product categories with higher potential in Europa and North-America. This is due to the low consumption of fish-, krill or algae-based products by these populations and to the numerous beneficial health effects of omega-3 PUFA on human health (as recognized by the European Food Safety Authority, EFSA). However, omega-3 PUFA are highly susceptible to oxidation, which lead to the loss of nutritional value as well as the formation of unpleasant off-flavors and toxic compounds. Therefore, lipid oxidation must be prevented in order to successfully develop foods enriched with omega-3 PUFA.
Omega-3 PUFA can be added to foods as neat oils or as a “delivery system” such as microencapsulated oil powders and oil-in-water emulsions. Nevertheless, the development of alternative omega-3 PUFA delivery systems, which are easy to disperse and which will lead to improved oxidative stability of omega-3 enriched food products, is required by the food industry in order to benefit the consumer.

In this regard, the ELECTRONANOMEGA project aimed at developing: i) advanced omega-3 nano-microdelivery systems by using electrohydrodynamic processes, and ii) fortified food containing these delivery systems. Electrospinning and electrospraying processes allow the encapsulation of bioactive compounds in nano-microfibers or nano-microcapsules, respectively. These processes, in contrast to spray-drying, do not require heat for the drying of the parent emulsion which is beneficial for the stability of thermo-sensitive compounds such as omega-3 PUFA. Moreover, nano-microcapsules obtained by electrospraying have a reduced size compared to microcapsules produced by spray-drying. This is beneficial both in terms of incorporation of the encapsulates into the food matrix and of the release of the bioactive compound, but it is a challenge in terms of oxidative stability due to a larger specific surface area.

Overall, ELECTRONANOMEGA project has delivered the following:
- Suggestions of type of biopolymers (incl. concentration and type of solvents) and process conditions for the production of nano-microstructures containing omega-3 PUFA by electrohydrodynamic processes.
- Optimum approaches to incorporate fish oil and natural antioxidants in order to improve the oxidative stability of the biopolymeric nano-microstructures.
- Nano-microstructures (both nano-microfibers and capsules) with appropriate structural-functional properties and with adequate oxidative stability after production.
- Process conditions selected for the incorporation of fish oil-loaded nano-microcapsules into mayonnaise (40 wt%. total fat). Fortified mayonnaise with good structural-functional properties has successfully been produced.

It has to be mentioned that the oxidative stability during storage of the nano-microstructures obtained and of the enriched mayonnaise needs to be further improved. In this regard, it seems necessary to further reduce the oil droplets on the surface (or close to the surface) of the nano-microsctructures, which are easily oxidized due to its large area of contact with prooxidants.
An overview of the work performed and the results obtained in the ELECTRONANOMEGA project is given below:
- Fish oil-loaded PVA or pullulan nano-microfibers were developed by emulsion electrospinning. Pullulan nano-microfibers presented a significant improved oxidative stability than PVA fibers. Moreover, pullulan nano-microfibers where the oil was added as neat to the pullulan solution (without any previous emulsification), were preferred in terms of oxidative stability. In addition, the oxidation of the fish oil loaded in these fibers was further decreased by using a combination of natural synergistic antioxidants such as delta-tocopherol (500 ppm) and rosemary extract (500 ppm).
- Fish oil-loaded nano-microcapsules were obtained by electrospraying by using combinations of whey protein, pullulan and dextran or glucose syrup. Capsules where the oil was incorporated using a rotor-stator emulsification showed a higher oxidative stability than capsules containing emulsified oil by high-pressure homogenization. This was explained by a higher encapsulation efficiency and larger droplets (with lower specific surface area). When comparing capsules produced with different carbohydrates, it was observed that glucose syrup capsules presented less oxidation probably due to the lower molecular weight of glucose syrup (when compared to dextran), which implies lower free volume reducing oxygen diffusivity. The oxidative stability of dextran capsules was improved by using an antioxidant extract obtained brown seaweed Fucus Vesiculusus. The same extract did not improve the oxidative stability of glucose capsules, which was achieved instead when using a combination of natural synergistic antioxidants such as delta-tocopherol (500 ppm) and rosemary extract (500 ppm).
- Mayonnaise (40 wt.% total lipid content) was enriched with glucose syrup capsules both without and with natural antioxidants (e.g. delta-tocopherol and rosemary extract) in order to have a fish oil content of 2.5 wt%. Processing conditions were optimized in order to obtain an enriched mayonnaise containing the capsules which was physically stable during one month storage. An increase in droplet size was observed but no creaming occurred during storage. In terms of oxidative stability, the capsules-containing mayonnaises were more oxidized than the mayonnaise enriched with neat fish oil (both in terms of primary and secondary oxidation products). The addition of antioxidants did not reduce lipid oxidation in the final product. Thus, further research is needed to improve oxidative stability of the micro-nanocapsules during storage and when incorporated into mayonnaise.

These results have been disseminated so far in 4 scientific published articles and 6 oral presentations in international scientific conferences. Moreover, the project results have been also disseminated by other means such as project website, DTU website, Researchgate, talk to students at the University of Granada (Spain) and popular science article in Inform Magazine.
ELECTRONANOMEGA project has led to an important advance in the protection against oxidation of omega-3 PUFA by encapsulation through electrohydrodynamic processes. Particularly, in this project:
- Novel fish oil-loaded nano-microstructures have been developed (e.g. pullulan nano-microfibers and nano-microcapsules having combinations of whey protein, pullulan and dextran or glucose syrup as wall materials).
- Novel approaches to incorporate fish oil into nano-microstructures have been studied (e.g. emulsion electrospinning or electrospraying).
- Novel strategies to further stabilize the encapsulated fish oil in the nano-microstructures have been investigated (e.g. addition of natural antioxidants such as delta-tocopherol, rosemary extract and seaweed extract).
- The scale-up of the strategies developed in lab scale has been achieved in collaboration with industry (e.g. Bioinicia, S.A. Spain).

Therefore, the knowledge generated in ELECTRONANOMEGA project has the potential to being exploited by companies devoted to the production of functional foods containing omega-3 lipids. Particularly, industry has shown its interest in our novel bio-polymer matrices, as alternative to zein, for the encapsulation of omega-3 PUFA.
Encapsulation of omega-3 polyunsaturated fatty acids by electrospinning or electrospraying processes