Oxidative stability differences of aqueous model systems of photoautotrophic n–3 LC–PUFA rich microalgae: The antioxidative role of endogenous carotenoids

Abstract

Microalgae rich in omega-3 long-chain polyunsaturated fatty acids (n–3LC–PUFA) have already shown their potential for developing functional food rich in these healthy fatty acids. Not only could they offer a more sustainable alternative for the fish stock that is currently relied upon but is unable to keep up with the demand, enrichment with certain microalgae also leads to oxidatively stable products. Although the reason for this stability has been attributed to the presence of endogenous carotenoids, further insight into their antioxidative role is missing and would be clarifying for selecting the proper microalgae for food enrichment. In trying to further accomplish this, a storage experiment (4 weeks, 37 °C) was set up with the parallel analysis of both oxidation products (primary and secondary) and carotenoids of two aqueous model systems of different (promising) microalgae (Nannochloropsis and Phaeodactylum). The results showed a clear difference in oxidative stability despite both microalgae containing endogenous carotenoids: Nannochloropsis led to oxidatively unstable and Phaeodactylum to oxidatively stable products. This was clearly confirmed by the analysis of n–3LC–PUFA throughout storage which showed a breakdown of half of the n–3LC–PUFA for Nannochloropsis. All carotenoids (violaxanthin, zeaxanthin and β-carotene for Nannochloropsis, and fucoxanthin and β-carotene for Phaeodactylum) acted as an antioxidant as shown by their degradation throughout storage, but the difference in oxidative stability pointed out an impact of carotenoid content and (possibly) type. The presence of a sufficient amount of carotenoids seems to be an important factor for perceiving oxidative stability. Phaeodactylum has shown to be more potent for food enrichment.