Tracking Cyanogenic Potentials of Cassava Tuber Processing into “GARI” from Farm to Table and Assessing Toxicity Levels

Abstract

The most important requirement in the processing of cassava tubers into "gari", an important African food, is its detoxification by the reduction of the total cyanide content (bound or free) to an acceptable level. Cyanogenic glucoside is referred to as bound cyanide while hydrocyanic acid (HCN) is referred to as free cyanide. The study was conducted to examine the cyanide level at every step and stage in "gari" processing chain. The study was conducted in Onipepeye, Oremeji, Agugu cassava processing industry in Ibadan, Nigeria. A multistage random sampling technique was used to select one processor out of 20 processors screened. Sixteen samples from the processing steps of raw, fermented and finished (ready to eat) cassava food product were analyzed for cyanide (toxicity) level using Good Manufacturing Practices (GMP) concept. Analysis of Variance (ANOVA) and T-test were used to determine significant differences in "gari" processing steps and stages for cyanide level changes. Post HOC Test was used to identify processing step(s) that contributed to the significant level differences in the cyanide level or toxicity in the "gari" processing steps. Changes in cyanide levels associated with "gari" processing steps were computed at 5% confidence level. The mean cyanide level (mg HCN eq. Average/100 gm) in "gari", unpeeled cassava 3.622, peeled cassava 9.35, peeled and washed cassava 10.16, pressed mash 7.48, "gari" hold and sell 2.09, showed significant changes in cyanide level (p < 0.0001). Post HOC Test showed that many step(s) contributed to the significant level differences in the cyanide level or toxicity. At the step of unpeeled cassava, peeled cassava, peeled and washed cassava, grated mash (fermented), sieved mash, fried "gari" from pan to ready-to-eat "gari" and held at 0.05% level, some mean differences in the processing step(s) contributed to the statistically significant difference in the cyanide level or toxicity in "gari" processing stages. This study shows that there is statistically significant difference in cyanide level (toxicity) among "gari" processing steps.