Cyanogenesis in Macadamia and Direct Analysis of Hydrogen Cyanide in Macadamia Flowers, Leaves, Husks, and Nuts Using Selected Ion Flow Tube-Mass Spectrometry.

Hardy Z Castada,Xuesong Huang,Sheryl Ann Barringer,Jinyi Liu

doi:10.3390/foods9020174

Abstract

Macadamia has increasing commercial importance in the food, cosmetics, and pharmaceutical industries. However, the toxic compound hydrogen cyanide (HCN) released from the hydrolysis of cyanogenic compounds in Macadamia causes a safety risk. In this study, optimum conditions for the maximum release of HCN from Macadamia were evaluated. Direct headspace analysis of HCN above Macadamia plant parts (flower, leaves, nuts, and husks) was carried out using selected ion flow tube–mass spectrometry (SIFT-MS). The cyanogenic glycoside dhurrin and total cyanide in the extracts were analyzed using HPLC-MS and UV–vis spectrophotometer, respectively. HCN released in the headspace was at a maximum when Macadamia samples were treated with pH 7 buffer solution and heated at 50 °C for 60 min. Correspondingly, treatment of Macadamia samples under these conditions resulted in 93–100% removal of dhurrin and 81–91% removal of total cyanide in the sample extracts. Hydrolysis of cyanogenic glucosides followed a first-order reaction with respect to HCN production where cyanogenesis is principally induced by pH changes initiating enzymatic hydrolysis rather than thermally induced reactions. The effective processing of different Macadamia plant parts is important and beneficial for the safe production and utilization of Macadamia-based products.

Highlights

IntroductionIn addition to Macadamia nuts, Macadamia flowers, husks, leaves, and shells are widely used as a source of functional foods, beverages, and raw materials in cosmetics, feed, and other applications
Macadamia-based commercial products have rapidly increased in recent years
At higher heating temperatures, cyanide production decreased, which could be caused by decreased enzyme activity or inactivation and, reduced subsequent hydrolysis reaction of the main cyanogenic glycoside dhurrin (Figure 4A)

Summary

Introduction

In addition to Macadamia nuts, Macadamia flowers, husks, leaves, and shells are widely used as a source of functional foods, beverages, and raw materials in cosmetics, feed, and other applications. Abundant antioxidant substances, such as polyphenols, can be extracted from Macadamia skin and husks for utilization in the food and pharmaceutical industries [1,2,3]. Species within the genus Macadamia, contain cyanogenic glycoside compounds, which are secondary metabolites that release hydrogen cyanide through cyanogenesis [6,7].

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Results

Conclusion