# Physicochemical Stability and Bio-Functionality of Liposome-Encapsulated Macadamia Husk Phenolic Extract

## TL;DR

This study shows that encapsulating macadamia husk antioxidants in liposomes improves their stability and controlled release, making them suitable for functional foods.

## Contribution

Liposomal encapsulation of macadamia husk phenolics is proposed as a novel method to enhance stability and controlled release for food applications.

## Key findings

- MHPE-loaded liposomes had nano-sized particles (77–78 nm) with low PDI and high encapsulation efficiency.
- Encapsulated MHPE showed slower phenolic release compared to the free extract under simulated gastrointestinal conditions.
- Liposomal encapsulation maintained MHPE stability for two months and was non-cytotoxic to Caco-2 cells.

## Abstract

Macadamia husks are an underutilized by-product of nut processing and a rich source of phenolic compounds with strong antioxidant activity. However, their instability during processing, storage, and gastrointestinal digestion limits their application in food systems. This study aimed to encapsulate macadamia husk phenolic-rich extract (MHPE) in liposomes to improve stability, enable controlled release, and assess cytotoxicity for functional food applications. MHPE was encapsulated in soy lecithin liposomes using high-shear mixing followed by high-pressure homogenisation. Liposomes were characterized by particle size, polydispersity index (PDI), ζ-potential, encapsulation efficiency, and morphology. Cytotoxicity was evaluated using Caco-2 cells, and phenolic release was assessed under simulated gastrointestinal conditions. MHPE-loaded liposomes exhibited nano-sized particles (77–78 nm), low PDI (0.21), and high negative ζ-potential (−43.11 to −47.01 mV) during two months of storage at 4 °C. Transmission electron microscopy confirmed predominantly spherical vesicles with sizes consistent with dynamic light scattering measurements. Encapsulation efficiency remained high (81.50% initially; 73.60% after 28 days). Both free and extract-loaded liposomes were non-cytotoxic to Caco-2 cells. Encapsulated MHPE showed slower phenolic release compared with the free extract. Overall, liposomal encapsulation effectively enhanced the stability and controlled release of macadamia husk phenolics, supporting their potential use as functional food and nutraceutical ingredients.