Short communication Total cyanide content of cassava food products in Australia Anna E. Burns a , J. Howard Bradbury b , Timothy R. Cavagnaro a,c , Roslyn M. Gleadow a, * a School of Biological Sciences, Faculty of Science, Monash University, Clayton, VIC 3800, Australia b Research School of Biology, Australian National University, Canberra, ACT 0200, Australia c Australian Centre for Biodiversity, Monash University, Clayton, VIC 3800, Australia 1. Introduction Cassava (Manihot esculenta Crantz, Euphorbiaceae) is the sixth most important food crop globally, in terms of annual production (FAOSTAT, 2010), and is a staple food for approxi- mately 800 million people (FAO/IFAD, 2000; Lebot, 2009). This perennial root crop is grown in the tropics, including sub- Saharan Africa, Asia, the Pacific Islands, and Central and South America (Hillocks et al., 2002; Lebot, 2009; McKey et al., 2010; Burns et al., 2010). The starchy tuberous roots are the main food source, but the young leaves, which are high in protein, are also consumed, particularly in Africa (Achidi et al., 2005; Lebot, 2009; Montagnac et al., 2009a). Cassava contains two cyanogenic glucosides, linamarin and a small amount of lotaustralin, which are catalytically hydrolysed to release toxic hydrogen cyanide (HCN) when the plant tissue is crushed (Conn, 1981; Balagopalan et al., 1988; McMahon et al., 1995). Cyanide inhibits cellular respiration of all aerobic organisms by blocking mitochondrial electron transport and preventing oxygen uptake (Solomonson, 1981). High exposure to cyanide in humans causes nausea, vomiting, diarrhoea, dizziness, weakness and sometimes death (Akintonwa et al., 1994; Cliff and Coutinho, 1995; Jones, 1998; Merck, 2008). Medical conditions caused by degeneration of the nervous system, konzo and tropical ataxic neuropathy (TAN), affect people who consume a monotonous diet of bitter (high cyanide) cassava (Cliff et al., 1985; Tylleskar et al., 1992; Osuntokun, 1994; Cliff and Coutinho, 1995; McKey et al., 2010; Burns et al., 2010). The low content of protein in cassava roots and the deficiency of sulphur amino acids in this protein can affect the health of regular consumers and may also be a risk factor for konzo (Nhassico et al., 2008; McKey et al., 2010). The range of total cyanide contents of different varieties of cassava is 1–1550 mg HCN equivalents/kg fresh material = ppm, in the root parenchyma and 900–2000 ppm in the root cortex (peel) (Mlingi and Bainbridge, 1994; Nambisan, 1994; Nambisan and Sundaresan, 1994; Cardoso et al., 2005). Cassava leaves contain 20–1860 ppm of total cyanide (Lancaster and Brooks, 1983; Bradbury and Denton, 2011). The World Health Organi- sation (WHO) set a safe limit of 10 ppm total cyanide for cassava flour (FAO/WHO, 1995). This maximum limit of 10 ppm has been adopted in Australia for cassava chips by Food Standards Journal of Food Composition and Analysis xxx (2011) xxx–xxx A R T I C L E I N F O Article history: Received 4 March 2011 Received in revised form 22 June 2011 Accepted 22 June 2011 Keywords: Cassava Manihot esculenta Crantz Cyanide Cyanogenic glucosides Cyanogenesis Toxins Food safety Picrate method Food processing Food analysis Food composition A B S T R A C T Cassava products obtained in two major Australian cities, Melbourne and Canberra, were analysed for total cyanide content using the picrate method. In Melbourne in 2010, ready to eat cassava chips were found to contain large amounts of cyanide with a mean value of 91 mg HCN equivalents/kg fresh weight = ppm. In Canberra, similar values were found over a six-year study with cassava chip samples, except for one sample that gave 7 ppm, which was obtained in 2011 after the introduction by Food Standards Australia and New Zealand of a 10 ppm maximum limit. In Melbourne, the highest value obtained was 262 ppm. A calculation based on this very high cyanide sample and using the lethal dose of cyanide for humans, shows that a child of 20 kg body weight would only need to eat 40–270 g of these chips to reach the lethal dose. Frozen cassava roots gave a mean value of 52 ppm total cyanide, which is also a cause for concern. In contrast, more highly processed foods contained < 1 ppm total cyanide. ß 2011 Elsevier Inc. All rights reserved. * Corresponding author. Tel.: +61 03 99 51667; fax: +61 03 990 54604. E-mail addresses: Burnsaanna.burns@monash.edu (A.E. Burns), howard.bradbury@anu.edu.au (J.H. Bradbury), timothy.cavagnaro@monash.edu (T.R. Cavagnaro), ros.gleadow@monash.edu (R.M. Gleadow). G Model YJFCA-2150; No. of Pages 4 Please cite this article in press as: Burns, A.E., et al., Total cyanide content of cassava food products in Australia. J. Food Compos. Anal. (2011), doi:10.1016/j.jfca.2011.06.005 Contents lists available at ScienceDirect Journal of Food Composition and Analysis jo u rn al ho m epag e: ww w.els evier .c om /lo cat e/jfc a 0889-1575/$ – see front matter ß 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2011.06.005