PGR News from the Pacific

Posted 7:43 PM by Luigi

Cyanide in Cassava

Following the recent spate of articles about cyanide in cassava, here's a contribution from Prof. Bill Aalbersberg of USP's Institute of Applied Science which tries to summarize our knowledge and set the record straight.

Cyanide occurs naturally in cassava (and other crops) as a glucoside. This is thought to be related to natural defence against pests. Cyanide, of course, is a potent poison and its presence in food crops has caused concern. Cassava has often been classed as “sweet,” or low in cyanide, or “bitter,” high in cyanide, though these correlations do not always hold. Concentrations in cassava range from roughly 10-1000 mg/kg of raw root. Pacific cultivars are usually classed as “sweet,” though during droughts Tonga reports they might taste bitter.

Health effects are not simple to predict based on cyanide content of the cassava. First of all, total cyanide removal by processing is variable. Simple boiling, which removes 50-60% of the cyanide, is sufficient in the Pacific for low cyanide cultivars, whereas in Africa, with higher average levels of cyanide, traditional processing involves a complex process of grating, fermentation and frying. The fate of the remaining cyanogenic glycoside during digestion - that is, how much is released as cyanide in the body - is not well known.

Cyanide in the body is mainly detoxified by reaction of sulphur-containing amino acids. The thiocyanide produced blocks iodine uptake by the thyroid gland. Thus, neurological disorders and lack of mental and physical development are the hallmarks of chronic intake of high cyanide varieties. More acute effects, even death, can occur if this is combined with improper food processing and malnourishment (lack of the sulphur containing amino acids).

In this somewhat murky scientific situation, New Zealand regulators decided to “protect” their consumers from cassava poisoning by calculating a worse-case scenario that all cyanide in the cyanogenic glycoside of raw cassava ended up as cyanide in the body. With some safety factor, this yielded a figure of 50 mg/kg as the safe limit for cyanide in cassava. Using the data of Bradbury from the 1980s that all Pacific cassava cultivars fell below this level, it was felt that this regulatory level would create no barrier to the considerable trade of cassava from Pacific island countries to New Zealand.

Unfortunately, the published research by Aalbersberg showing that most cultivars in Fiji contained more than 50 mg/kg and suggesting that the Bradbury samples were likely compromised during their journeys to his laboratory in Australia seems not have been consulted.

Since then, Tonga samples have also been analysed and all mature cultivars are above 50 mg/kg. The absence of goitre in Tonga, which would be an early sign of possible health effects from cassava consumption, suggests that Pacific islanders can consume large amounts of cassava that have moderate levels of cyanide without apparent health effects. This suggest that regulators need to relook at this issue.



	A blog maintained by Tevita Kete, PGR Officer Secretariat of the Pacific Community (SPC), Suva, Fiji Islands
This weblog documents the activities of Pacific Agricultural Genetic Resources Network (PAPGREN), along with other information on plant genetic resources (PGR) in the Pacific. The myriad varieties found within cultivated plants are fundamental to the present and future productivity of agriculture. PAPGREN, which is coordinated by the Land Resources Division of the Secretariat of the Pacific Community (SPC), helps Pacific countries and territories to conserve their crop genetic diversity sustainably, with technical assistance from the Bioversity International (BI) and support from NZAID and ACIAR. SPC also hosts the Centre of Pacific Crops and Trees (CEPaCT). The CEPaCT maintains regional in vitro collections of crops important to the Pacific and carries out research on tissue culture technology. The CEPaCT Adviser is Dr Mary Taylor (MaryT@spc.int), the CEPaCT Curator is Ms Valerie Tuia (ValerieT@spc.int). PAPGREN coordination and support IPGRI ACIAR NZAID CTA SPC PAPGREN CEPaCT Click on the thumbnail to see a map of the locations of Pacific genebanks. Click here to download a regional directory of genebanks in the Pacific, including information on their location, contact details and holdings. PAPGREN partners Mr William Wigmore Director of Research Ministry of Agriculture Department of Resources & Development P.O. Box 96 Rarotonga Cook Islands Tel: (682) 28711-29720 Fax: (682) 21881 Email: cimoa@oyster.net.ck Mr Adelino S. Lorens Chief Agriculture Pohnpei Office of Economic Affairs P.O. Box 1028 Kolonia Pohnpei 96941 Federated States of Micronesia Tel: (691) 3202400 Fax: (691) 3202127 Email: pniagriculture@mail.fm Dr Lois Englberger Island Food Community of Pohnpei Research Advisor P.O. Box 2299 Kolonia Pohnpei 96941 Federated States of Micronesia Email: nutrition@mail.fm Mr Apisai Ucuboi Director of Research Ministry of Agriculture, Fisheries & Forest Koronivia Research Station P.O. Box 77 Nausori Fiji Islands Tel: (679) 3477044 Fax: (679) 3477546-400262 Email: apisainu@yahoo.com Dr Maurice Wong Service du Developpement Rural B.P. 100 Papeete Tahiti 98713 French Polynesia Tel: (689) 42 81 44 Fax: (689) 42 08 31 Email: maurice.wong@rural.gov.pf Mr Tianeti Beenna Ioane Head, Research Section Division of Agriculture Ministry of Environment, Lands and Agricultural Development P.O. Box 267 Tarawa Kiribati Tel: (686) 28096-28108-28080 Fax: (686) 28121 Email : agriculture@tskl.net.ki; Beenna_ti@yahoo.com Mr Frederick Muller Secretary Ministry of Resources & Development P.O. Box 1727 Majuro 96960 Marshall Islands Tel: (692) 6253206 Fax: (692) 6257471 Email: rndsec@ntamar.net Mr Herman Francisco Director Bureau of Agriculture Ministry of Resources & Development P.O. Box 460 Koror 96940 Palau Tel: (680) 4881517 Fax: (680) 4881725 Email: bnrd@pnccwg.palaunet.com Ms Rosa Kambuou Principal Scientist PGR NARI Dry Lowlands Programme Laloki Agricultural Research Station P.O. Box 1828 Boroko National Capital District Papua New Guinea Tel: (675) 3235511 Fax: (675) 3234733 Email: kambuou@global.net.pg Ms Laisene Samuelu Principal Crop Development Officer Crops Division Ministry of Agriculture, Forests, Fisheries & Meteorology P.O. Box 1874 Apia Samoa Tel: (685) 23416-20605 Fax: (685) 20607-23996 Email: lsamuelu@lesamoa.net Mr Jimi Saelea Director of Research Department of Agriculture and Livestock P.O. Box G13 Honiara Guadalcanal Solomon Islands Tel: (677) 27987 Mr Tony Jansen Planting Materials Network Kastom Gaden Association Burns Creek, Honiara P.O. Box 742 Honiara Solomon Islands Tel: (677) 39551 Email: kastomgaden@solomon.com.sb Mr Finao Pole Head of Research Ministry of Agriculture & Forests P.O. Box 14 Nuku'alofa Tonga Tel: (676) 23038 Fax: (676) 24271 Email: thaangana@hotmail.com Mr Frazer Bule Lehi Head of Research Department of Agriculture & Rural Development Private Mail Bag 040 Port Vila Vanuatu Tel: (678) 22525 Fax: (678) 25265 Email: flehi@hotmail.com Other links Other CROP agencies Forum Secretariat University of the South Pacific SPREP Pacific biodiversity Biodiversity hotspots Breadfruit Institute Hawaiian native plants Intellectual property rights Nature Conservancy PBIF PestNet SIDS WWF South Pacific Program Other Pacific organizations Foundation of the Peoples of the South Pacific Micronesian Seminar Te Puna web directory Pacific news Cafe Pacific CocoNET Wireless Island Directory Pacific Islands News Pacific Islands Report Pacific Islands Travel Pacific Time South Pacific travel Time Pacific Interested in GIS? DIVA-GIS	Sunday, May 08, 2005 Posted 7:43 PM by Luigi Cyanide in Cassava Following the recent spate of articles about cyanide in cassava, here's a contribution from Prof. Bill Aalbersberg of USP's Institute of Applied Science which tries to summarize our knowledge and set the record straight. Cyanide occurs naturally in cassava (and other crops) as a glucoside. This is thought to be related to natural defence against pests. Cyanide, of course, is a potent poison and its presence in food crops has caused concern. Cassava has often been classed as “sweet,” or low in cyanide, or “bitter,” high in cyanide, though these correlations do not always hold. Concentrations in cassava range from roughly 10-1000 mg/kg of raw root. Pacific cultivars are usually classed as “sweet,” though during droughts Tonga reports they might taste bitter. Health effects are not simple to predict based on cyanide content of the cassava. First of all, total cyanide removal by processing is variable. Simple boiling, which removes 50-60% of the cyanide, is sufficient in the Pacific for low cyanide cultivars, whereas in Africa, with higher average levels of cyanide, traditional processing involves a complex process of grating, fermentation and frying. The fate of the remaining cyanogenic glycoside during digestion - that is, how much is released as cyanide in the body - is not well known. Cyanide in the body is mainly detoxified by reaction of sulphur-containing amino acids. The thiocyanide produced blocks iodine uptake by the thyroid gland. Thus, neurological disorders and lack of mental and physical development are the hallmarks of chronic intake of high cyanide varieties. More acute effects, even death, can occur if this is combined with improper food processing and malnourishment (lack of the sulphur containing amino acids). In this somewhat murky scientific situation, New Zealand regulators decided to “protect” their consumers from cassava poisoning by calculating a worse-case scenario that all cyanide in the cyanogenic glycoside of raw cassava ended up as cyanide in the body. With some safety factor, this yielded a figure of 50 mg/kg as the safe limit for cyanide in cassava. Using the data of Bradbury from the 1980s that all Pacific cassava cultivars fell below this level, it was felt that this regulatory level would create no barrier to the considerable trade of cassava from Pacific island countries to New Zealand. Unfortunately, the published research by Aalbersberg showing that most cultivars in Fiji contained more than 50 mg/kg and suggesting that the Bradbury samples were likely compromised during their journeys to his laboratory in Australia seems not have been consulted. Since then, Tonga samples have also been analysed and all mature cultivars are above 50 mg/kg. The absence of goitre in Tonga, which would be an early sign of possible health effects from cassava consumption, suggests that Pacific islanders can consume large amounts of cassava that have moderate levels of cyanide without apparent health effects. This suggest that regulators need to relook at this issue. * Comments: Post a Comment	Archive October 2002 November 2002 December 2002 January 2003 February 2003 March 2003 April 2003 May 2003 June 2003 July 2003 August 2003 September 2003 October 2003 November 2003 December 2003 January 2004 February 2004 March 2004 April 2004 May 2004 June 2004 July 2004 August 2004 September 2004 October 2004 November 2004 December 2004 January 2005 February 2005 March 2005 April 2005 May 2005 June 2005 July 2005 August 2005 September 2005 October 2005 November 2005 December 2005 January 2006 February 2006 March 2006 April 2006 May 2006 June 2006 July 2006 August 2006 September 2006 October 2006 November 2006 December 2006 January 2007 February 2007 March 2007 April 2007 May 2007 June 2007 July 2007 August 2007 September 2007 October 2007 November 2007 December 2007 January 2008 February 2008 March 2008 April 2008 May 2008 June 2008 July 2008 August 2008 September 2008 October 2008 November 2008 December 2008 January 2009 February 2009 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 September 2009 October 2009 November 2009 January 2010 RSS Feed Alternative feed Contact Tevita Something new: Agrobiodiversity Weblog: For discussions of conservation and sustainable use of the genetic resources of crops, livestock and their wild relatives. PestNet: For on-line information, advice and pest identification for the Pacific and beyond. Contact: Grahame Jackson. Pacific Mapper: For on-line mapping of point data over satellite images of the Pacific provided by Google Maps. DIVA-GIS: For free, easy-to-use software for the spatial analysis of biodiversity data.