Encapsulation of eugenol using Maillard-type conjugates to form transparent and heat stable nanoscale dispersions

Maillard-type protein-carbohydrate conjugates are known for their excellent emulsifying properties and have been used to encapsulate volatile oils and flavor compounds. In the present study, eugenol was used as a model compound for encapsulation in conjugates of whey protein isolate (WPI) and maltodextrins (MD) made using different WPI:MD mass ratios and MD chain lengths. The encapsulation involved two steps, emulsifying an oil phase of eugenol dissolved in hexane into an aqueous phase with dissolved conjugates and spray drying the emulsion. Mass yield up to 82.7 g/100 g and encapsulation efficiency as high as 35.7 g/100 g eugenol were observed. After hydrating spray-dried powders, several samples with an eugenol content above its solubility limit demonstrated transparent dispersions at pH 3.0 and 7.0 after heating at 80 degrees C for 15 min, corresponding to mean diameters smaller than ca. 100 nm. One treatment also showed transparent dispersions after heating at pH 5.0, which is near the isoelectric point of whey proteins, in contrast to gel formation for a control prepared with a mixture of non-conjugated WPI and MD. The present study demonstrates potential to produce food grade nanoscale systems for delivering lipophilic bioactives in functional beverages, without adversely affecting their visual appearance. (C) 2012 Elsevier Ltd. All rights reserved.