DETERMINATION OF THE CRITICAL TIME WHEN LEVELS OF THE CYANIDE POTENTIAL IN CASSAVA ARE AT PEAK CONCENTRATION

Abstract

Cassava (Manihot esculanta Crantz) is the second most important food crop and a main source of income for the rural communities with potential for industrial use in the coastal region of Kenya. Cassava, now widely grown in the coastal region of Kenya is a domesticated plant derived from one or more species of the Genus Manihot in the Euphorbiaceae family. Cassava contains naturally occurring, but potentially toxic compounds called cyanogenic glycosides, which release hydrogen cyanide (HCN) as a result of enzymatic hydrolysis following maceration of the plant tissue. The objective of the study was to sustain and enhance the food security and livelihood of coastal lowland farmers and processors by assisting them to successfully produce/trade/export their produce in compliance with food safety standards for cassava and cassava products. The study was to conduct a scientific assessment to determine ways along the food chain/commodity pathway to minimize the hydro cyanic acid content in cassava and its products and thus provide methods of meeting food quality standards requirement. This was achieved by determining, through study and analysis, the effect on cyanide content based on agronomic factors ( e.g. cultivars,  stress, ), agro ecological zone (CL 3, CL 4, and CL 5) and harvest/post-harvest practices i.e. age at harvest. The study was conducted in 2016 in Kilifi County in three agro ecological zones. They are coastal lowlands 3, 4 and 5. The genotypes studied and analyzed are Tajirika (improved), Shibe (improved), Karembo (improved) and Kibandameno (traditional). The analysis was carried out at 5, 8 and 11 months after planting. At five months after planting in loamy soils for the Kibandameno variety, the cyanide level is recorded 0.5mg/kg while at 11 months after planting in the same soils and AEZ’s, the level is 0.33mg/kg. At five months after planting, Tajirika, Shibe and Kibandameno varieties in CL5 recorded cyanide levels of 0.44 and 0.48mg/kg respectively in sandy loam soils. In the eleventh month, Shibe and Kibandameno varieties in the same soil type recorded 0.41 and 0.45 mg/kg, respectively. There is a slight indication that as the plant ages the levels of the cynogenic potential (CNP) declines.