Encapsulation of propolis extract in whey protein nanoparticles

The aim of this study was to investigate the antioxidant activity and phenolic compounds of propolis and to evaluate the possibility of encapsulation of propolis extract in the nanoparticles of whey protein (WPN) to increase protein's functionality and physicochemical characteristics. Nanoparticles were produced through freeze-drying. According to the total phenolic content and the antioxidant activities, extraction with 80% v/v ethanol was selected as the optimal process and was selected for the encapsulation. Three different complexes of 1%, 2.5%, and 4% propolis extract (g propolis/100 g protein) including whey protein nanoparticles were obtained at pH values 3.2 and 7.5. Fluorescence spectroscopy revealed that propolis-WPN complexes were formed mainly through hydrophobic interactions. In addition, the intensity of propolis peaks in XRD decreased or the peaks disappeared after encapsulation, showed that the crystallization phase of propolis was reduced or changed to an amorphous phase. Besides, FTIR results confirmed some hydrogen and hydrophobic bonds between components. Moreover, an increase in the amount of propolis led to the more controlled release in gastrointestinal digestion. Eventually, it was found that the compositions 4% pH: 3.2 and 4% pH: 7.5 had the most suitable characteristics to be further used in various food applications. •Propolis extract was a rich source of polyphenolic compounds mainly flavonoids.•Whey protein nanofibrils (WPN) were suitable carriers for propolis in terms of maintaining its functionalities.•WPN-propolis complexes were resistant to the stomach-like conditions and exhibited controlled digestion.•Non-covalent bonds were the most interaction mechanism of WPN-propolis complexes.