(373d) Nano Liposomes for the Encapsulation of a Food Preservative

Preservation of food surfaces to avoid contamination by micro-organisms and spoilage is a recurring concern of the food industry. Protection can be obtained by applying on food surfaces coatings containing particles of poorly water-soluble preservative ingredients. However, these preservatives are often degraded through unfavourable environmental factors (light, heavy metals, etc…) and loose their efficiency. Encapsulation systems able to protect the preservatives from degradation and possibly to provide a controlled release of these compounds are nowadays highly desired by the food industry. Among the considered encapsulation systems, liposomes [1] are of great interest due to their low toxicity, their food-grade components, their versatility and their ability to entrap a great variety of lipophilic and amphiphilic compounds.

In this work, nano-liposomes were prepared from commercial soybean lecithins using the solvent shifting method known as “nano-precipitation” developed by Fessi et al. [2]. The formation of a colloidal suspension of nano-liposomes was obtained by transferring a solution of lecithins in methanol into an aqueous phase. A systematic study was performed by dynamic light scattering to determine the influence of several factors (lecithin concentration, ratio methanol/water, pH, salt content, stirring rate, etc…) on the size and polydispersity of the suspensions.  Cryo-TEM pictures were taken and pointed out the formation of spherical small unilamellar vesicles (Fig.1). The incorporation of the preservative compound was then performed. The obtained suspensions were characterized by DLS and the influence of the ratio lecithin/preservative assessed. The encapsulation yield of the preservative was determined and optimized. Microbiological tests were carried out to evaluate the interest of nano-liposomes compared to non encapsulated forms of the same preservative compound.

References

[1] M.R.Mozafari, C.Johnson, S.Hatziantoniou, C.Demetzos, Nanoliposomes and their applications in food nanotechnology, Journal of Liposome Research, 2008, 18, 309-327

[2] S.Stainmesse, H.Fessi, J.-P.Devissaguet, F.Puisieux, Process for the preparation of dispersible colloidal systems of amphiphilic lipids in the form of submicronic liposomes, EP0349429