Total cyanide content of cassava food products in Australia

Abstract

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.