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Different microalgal species are a sustainable, alternative source of omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) and can be incorporated into the food chain. However, the impact of microalgal species, photoautotrophic versus heterotrophic, on the enrichment of food products with n-3 LC-PUFA and their oxidative stability has never been studied before. This study provides greater insight into the impact of the microalgal species in enriched tomato puree. Therefore, four microalgal species (three photoautotrophic: Isochrysis, Nannochloropsis and Phaeodactylum and one heterotrophic: Schizochytrium) were compared to each other and analyzed for their amount of n-3 LC-PUFA, antioxidants, free fatty acids and lipid oxidation products. Photoautotrophic microalgal species were able to create a tomato puree rich in n-3 LC-PUFA without compromising the oxidative stability. On the other hand, tomato puree, although rich in antioxidants, was not able to keep the n-3 LC-PUFA in purees supplemented with Schizochytrium biomass oxidatively stable.

No abstract

Several species of microalgae are promising as an alternative source of omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). Photoautotrophic species show the greatest potential, since incorporating them into food products leads to oxidatively stable products; however, the presence of photosensitizers could reduce the shelf-life due to the appearance of photo-oxidation on exposure to light. This study investigated the oxidative impact of illumination for aqueous model suspensions enriched with Phaeodactylum (phototrophic microalgaecontaining potential photosensitizers) and Schizochytrium (heterotrophic microalgaelacking photosensitizers) during storage for 28 days at 37 °C. Primary (peroxide value) and secondary (volatiles with gas chromatography (GC)–mass spectrometry) oxidation products, n-3 LC-PUFA content (GC), and pigments (high-pressure liquid chromatography) were assessed. The results showed that photo-oxidation did not cause oxidative instability for Phaeodactylum samples compared with strong autoxidation in Schizochytrium samples. For the Phaeodactylum-enriched suspensions, only minimal photo-oxidation could be detected and the n-3 LC-PUFA content remained stable throughout storage regardless of illumination.

Worldwide, fish oil is an important and rich source of the health-beneficial omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA). It is, however, troubled by its high susceptibility towards lipid oxidation. This can be prevented by the addition of (preferably natural) antioxidants. The current research investigates the potential of Phaeodactylum carotenoids in this regard. The oxidative stability of fish oil and fish oil with Phaeodactylum addition is evaluated by analyzing both primary (PV) and secondary (volatiles) oxidation products in an accelerated storage experiment (37 °C). A first experimental set-up shows that the addition of 2.5% (w/w) Phaeodactylum biomass is not capable of inhibiting oxidation. Although carotenoids from the Phaeodactylum biomass are measured in the fish oil phase, their presence does not suffice. In a second, more elucidating experimental set-up, fish oil is mixed in different proportions with a Phaeodactylum total lipid extract, and oxidative stability is again evaluated. It was shown that the amount of carotenoids relative to the n-3 LC-PUFA content determined oxidative stability. Systems with a fucoxanthin/n-3 LC-PUFA ratio ≥ 0.101 shows extreme oxidative stability, while systems with a fucoxanthin/n-3 LC-PUFA ratio ≤ 0.0078 are extremely oxidatively unstable. This explains why the Phaeodactylum biomass addition did not induce oxidative stability.