Improvement of Stability to Oxidation of Hydrophilic and Lipophilic Active Principles By Encapsulation in Colored Polysaccharide Hydrogels

Encapsulation of easily oxidized compounds is a common technique in order to protect them from the environment and prevent the lost of their functional properties. Some of these compounds can be added to foods in order to enrich them. In this work, ginger essential oil and vitamin C, as examples of lipophilic and hydrophilic compounds, are encapsulated.

The matrix used for encapsulation is a solution of alginate and kappa-carrageenan where the active principle is dissolved (vitamin C) or emulsified (ginger oil). Through the use of a Büchi-encapsulator, the mixture is then dripped in a solution of 1%CaCl₂-0.1%Chitosan as gelling agent and allowed to harden for 10 minutes.

This encapsulation procedure is carried out with plain mixtures, with red dyed mixtures (by addition of red natural dye mainly formed by natural extract of black carrot), and with blue dyed mixtures (by addition of methylene blue). The formed capsules are then located in several containers for a period of 30 days and subjected to different storage conditions of temperature, contact with light and contact with air. It is hypothesized that coloured capsules can offer major protection against oxidation as they decrease light exposure. Ginger oil oxidation is followed through measurement of peroxide value. Vitamin C oxidation is quantified by iodimetry. Non-encapsulated active principles are also used like control.

Results show that active principles are more protected when located in the fridge, where low temperature and absence of light decrease oxidation rate. Encapsulation retards degradation, indicating that encapsulation is relatively effective. On the other hand, the red capsules offer significantly better results than non-coloured capsules, contrary to what happens with blue capsules, indicating that methylene blue accelerates oxidation mechanisms.

Acknowledgements.The authors thank the Spanish Ministry of Economy and Competitiveness for financial support through project CTQ2016-80645-R, and the FEDER funds of the European Union