Development of a sensitive picrate method to determine total cyanide and acetone cyanohydrin contents of gari from cassava

The sensitivity of the normal picrate method for determination of total cyanide in cassava was increased tenfold using a small 1 cm² picrate paper, eluted using 0.5 mL instead of 5 mL of water as in the normal method. The absorbance was measured in a 2 mm cuvette in the spectrophotometer. The sensitive method was calibrated against the normal picrate method. The total cyanide content in mg HCN equivalents/kg sample = ppm, is calculated from the absorbance (A) by the equation ppm = A × 45.7 which is applicable from 0.1 to 50 ppm. A new method to determine acetone cyanohydrin was developed based on irreversible denaturation of linamarase in 0.1 M HCl at 30 °C for 1 h. Five gari samples from Mozambique gave a mean total cyanide content of 12 ppm (range 6–15 ppm) and mean acetone cyanohydrin content of 11 ppm (range 5–14 ppm). Acetone cyanohydrin liberates cyanide quantitatively in the human intestine.     

Sensory attributes and texture profile of beef burgers with gari

Beef burgers were produced using gari to substitute beef in the product formulations at 0% (control), 10%, 15% and 20% respectively. Cooking yield increased significantly (p<0.05) with increasing use of gari. Sensory evaluation of the products revealed significant (p<0.05) differences for acceptability and texture attributes. The acceptability score for burgers produced with 15% gari was not significantly different (p>0.05) from the control without gari. Using gari had no significant (p>0.05) effect on flavor and odor attributes of beef burgers. Texture profile analysis of burgers showed significant (p<0.05) reductions in hardness, springiness, gumminess and chewiness at all levels of substituting beef with gari. Production cost of burgers reduced by 9%, 14% and 18% respectively using 10%, 15% and 20% gari in burgers. The results suggest that gari has promising potential for use in comminuted meat products.     

Simple method to reduce the cyanogen content of gari made from cassava

The lactic acid content of gari, was determined by pH titration to be about 10 g lactic acid/kg gari. As the size of the gari particles increased from 400 to >1000 μm their total cyanide content increased from 5 to 21 ppm. The acetone cyanohydrin content of gari samples exposed to ambient laboratory conditions of temperature and relative humidity gradually decreased by 58% in 38 weeks whereas linamarin in cassava flour is 100% stable for 6 months. Cyanogens could not be removed from wet gari samples at 30 or 50 °C and were only slowly removed by repeated heating at 100 °C and rewetting. By mixing equal weights of gari (pH 4.1) and low cyanide cassava flour (pH 6.5), wetting and heating at 50 °C for 5 h, the cyanide content was reduced by about one half. Wetting a gari/flour (1:1) sample with 1.5 times its weight of water and standing in a 1 cm thick layer in the sun for 4 h reduced the cyanide content by about one half. This treated mixture may be cooked to prepare stiff porridge with lowered cyanide content, and may help reduce tropical ataxic neuropathy in West Africa.