Encapsulation of phenolic-rich lemon-scented tea tree extract in lemon pomace powder

The Australian native plant, lemon-scented tea tree (LSTT) is rich in polyphenols with strong antioxidant activities. Encapsulation enhances the potential applications of plant extracts and additionally protects them from degradation. The encapsulating agent is one of the key elements in the encapsulation process. In this study, lemon pomace powder (LPP) was investigated as a new carrier agent for LSTT leaf phenolic extract, and its performance was compared with the commonly used polysaccharide (i.e., maltodextrin (MD)) and protein-based (i.e., soy protein isolate (SPI)) coating materials. The encapsulation efficiency, colour, polyphenol and antioxidant property retention, particle morphology, crystallinity, flow properties, and release behaviour in food simulants and gastrointestinal fluid were studied to compare the performance of the carrier agents individually and in combinations. The encapsulation efficiency of lemon pomace powder (LPP) was above 95 % and the order for the retention of polyphenol and antioxidant capacities were MD>LPP>SPI. LPP offers better flow properties and unique particle morphology, which was also amorphous in nature with some degree of crystallinity. The release profile in the food simulants showed a controlled and sustained release rate over the tested period, which was comparable with MD and SPI. In gastrointestinal fluids, the percent release followed the order of SPI>LPP>MD for the carrier agents. The incorporation of LPP with MD and SPI can improve several properties of the individual carrier agents. Thus, LPP can be used as a potential carrier agent for polyphenols in functional food formulation either on its own or in combination with other coating materials.