Nanodispersing thymol in whey protein isolate-maltodextrin conjugate capsules produced using the emulsion–evaporation technique

Abstract

This work presents simple processes to prepare transparent aqueous dispersions of thymol, a lipophilic antimicrobial compound. The emulsion–evaporation technique involved the preparation of capsules by spray-drying oil-in-water emulsions containing thymol dissolved in hexane emulsified using conjugates of whey protein isolate and maltodextrin. Hydration of spray-dried capsules resulted in transparent and heat stable nanodispersions containing thymol at concentrations well above its solubility limit, even at pH around the isoelectric points of whey proteins. The efficiency of encapsulation and the heat-stability of nanodispersions were affected by the emulsion composition. An encapsulation efficiency of 51.4% was obtained for one sample that corresponded to dispersions, adjusted to pH 3.0–7.0, with mean diameters of <90nm after heating at 80°C for 15min. The present study demonstrates a promising technology to produce nanoscale systems for delivering lipophilic components in aqueous foods such as clear beverages.