Microencapsulation of phenolic compounds extracted from onion (Allium cepa) skin

The objective of this study was to investigate the effect of different coating materials for encapsulation of phenolic compounds extracted from onion skin. As coating material, maltodextrin (MD) was combined with gum Arabic (GA), casein, or whey protein concentrate (WPC) at different ratios (8:2 and 6:4). Encapsulation efficiency, antioxidant activity, particle size distribution, and heat stability were analyzed in freeze dried microcapsules. The encapsulation efficiency values were found to be highest with MD–casein combination coating material (84.39–89.15%). There was no significant difference between coating material types in terms of antioxidant activity (p > .05). Capsules with MD–protein combination coating material had the smallest Sauter mean diameter values. Usage of MD–casein combination as a coating material increased heat stability of capsules. Practical applications Onion skin contains phenolic compounds which are important in terms of their health promoting effects. However, phenolic compounds are susceptible to external factors like light, heat, or pH changes. Encapsulation is a good method to protect these unstable compounds and to mask their undesired taste. Usage of different novel coating materials are important for encapsulation of phenolic compounds from onion skin to preserve these compounds against environmental stresses. The phenolic containing capsules obtained in this study could be incorporated to different food matrices. Since capsules obtained in this study were found to be stable against heat, they could be recommended to be used in especially thermal processed foods such as baked and fried foods.