Potential Toxic Levels of Cyanide in Cassava (manihot esculenta crantz) Grown in some Parts of Kenya

Abstract

Cassava (Manihot esculenta Crantz) is a cyanogenic plant which is toxic when consumed without sufficient processing. Cassava is characterized by presence of linamarin a cyanogenic glycoside and when acted upon by an enzyme linamarase is hydrolysed into cyanohydrin which is further hydrolyzed to give hydrogen cyanide (HCN) which is toxic. This study aimed at determination of the levels of cyanide in the sweet cassava variety grown in five different geographical regions of Kenya namely Kisii, Kakamega, Thika, Nairobi and Kitui counties. The picrate paper method whose accuracy was higher compared to picrate solution and titration methods was used. The study also reports on variation of cyanide concentration with cultivar type and its concentration in different parts of cassava root. The concentration of cyanide varied significantly (p<0.05), (n=324) with the geographical location. The concentration of cyanide in cassava from Kakamega was highest (80.79±4.55 mg/kg), while cassava from Kisii had the lowest cyanide concentration (43.27 ± 3.75 mg/kg). The cyanide concentration in cassava from Kitui was 70.46 ± 2.21 mg/kg, while Nairobi and Thika had cyanide concentration of 66.00 ± 2.12 mg/kg and 54.84 ± 0.65 mg/kg respectively. All the eight cultivars (990183, 990014, 990005, 990249, 990006, mm96/5280, ex manakari and 196/0067) analyzed for cyanide showed significant variation (p<0.05) in the cyanide content; 55.04±0.02, 44.27±0.07, 47.76±0.07, 48.68±0.07, 49.60±0.07, 45.88±0.07, 46.76±0.00 and 49.14±0.07 in mg/kg respectively. Three parts of cassava root (Pith, Parechyma and Cortex) contained significantly different concentrations of cyanide; 59.24±3.62, 78.35±2.13, 91.03±2.94 mg/kg respectively. The concentrations of cyanide in cassava from all the five regions were higher than the recommended level by WHO (10mg of HCN/kg body weight). This study provides critical information on the potential toxicity of cyanide in cassava from the five different regions