Design of flavonoid microparticles with channel forming properties to improve oxidative stability of sunflower oil

Abstract

For about a century, scientists and food technologists were puzzled trying to understand the chemistry of lipid oxidation and striving to find strategies to protect the unsaturated fatty acids in foods. For more than fifty years ago, it the free radical theory was accepted to explain the basic reaction mechanism and the involvement of product lipid hydroperoxides in autocatalysis of the reaction. Antioxidants were identified as components that are able, when present in micromolar concentrations, to provide significant protection and prolong the induction period of oxidizing fatty acids. Certain other compounds, defined as synergists, did not present antioxidant properties per se but were able to potentiate and improve the efficiency of antioxidants. The role of antioxidants and their protection efficacy were associated with a number of paradoxes pointing to a lack of proper understanding. Recently, oxidizing lipid systems have been defined as micro- or nano-emulsions wherein the oxidation and antioxidation sites are the interfaces between lipids and water. This new paradigm is expected to lead to significant progress in the understanding of the role of synergists and the potentiation of antioxidants actions. The article by Morelo et al. [1] in this issue of the European Journal of Lipid science & Technology is discussing a new idea for the addition of antioxidants to oxidizing fatty acids in a bulk oil model. Two flavonoid antioxidants, quercetin and epicatechin, were encapsulated in an oil insoluble carbohydrate polymer (inulin) and further covered with an oil-soluble soy protein isolate polymer by spray drying. Heating of these microencapsulates lead to the formation of channels within the particles that will aid the diffusion of the antioxidants to the lipid medium. As a proof of principle, the antioxidant potencies of the microparticles containing quercetin and epicatechin were tested in sunflower oil using the Rancimat at 60 °C. This work can be a start for new designs where not only antioxidants but also sensitive lipids and vitamins can be microencapsulated for protection.