Effect of extraction solvents on recovery of bioactive compounds and antioxidant properties from macadamia (Macadamia tetraphylla) skin waste

Adriana Dailey,Quan V Vuong,Fatih Yildiz

doi:10.1080/23311932.2015.1115646

Abstract

Macadamia is well known for its high-quality kernel; however, its skin and husk, known as waste, have had limited uses as by-products. This study aimed to determine the characteristics of the macadamia nut and to examine the impact of different solvents on the recovery of phenolic compounds (TPC), flavonoids, proanthocyanidins and antioxidant properties of the macadamia skin. The results showed that the kernel, the commercial part, only accounts for about 20% of the nut weight; whereas, the skin or the husk, the waste, account for approximately 40%, revealing that macadamia skin is an abundant starting material for the utilisation of by-products. The type of solvents was found to significantly affect the recovery yields of bioactive compounds from the macadamia skin. The combination of organic solvents, methanol, ethanol, acetonitrile and acetone with water (50%, v/v) had the highest recovery yields for TPC, flavonoids and proanthocyanidins as well as the most potent antioxidant properties, followed by absolute methanol, then water. Absolute ethanol, acetonitrile and acetone had the lowest recovery yields. The current study recommended that 50% acetone should be used for the recovery of TPC and flavonoids and 50% ethanol should be used for the extraction of proanthocyanidins from the macadamia skin.

Highlights

IntroductionNative Australian tree originating from the rainforest regions of Australia’s East Coast
Macadamia is an evergreen, native Australian tree originating from the rainforest regions of Australia’s East Coast
This means that there are about 80 thousand tons of macadamia skin produced annually in Australia and 280 thousand tons produced worldwide. These results reveal that macadamia skin is an abundant material, which undoubtedly is a great potential starting material for recovery of bioactive compounds for further utilisation

Summary

Introduction

Native Australian tree originating from the rainforest regions of Australia’s East Coast. Australia is the world’s largest macadamia-producing country generating approximately 40,000 tonnes per year, with approximately 70% of the nut’s weight being skin and husk, which are inedible These by-products are often treated as waste with little value (Wechsler et al, 2011). These by-products have been partially utilised in garden mulching, animal feed fillers, furniture materials and carbon composites for post-combustion CO2 capture, most of these by-products have been disposed of into landfill, which is a cost-prohibitive action through their sheer volume (Bae & Su, 2013; Wechsler et al, 2011), and this abundant source is a great starting material for bioactive compounds (Walton & Wallace, 2010). It is necessary to determine the most suitable solvent for recovery of bioactive compounds from macadamia skin

Objectives

Methods

Results

Conclusion