Résumé
This study investigated the effect of cooking time on starch and cyanide contents of freshly harvested cassava tubers used for tapioca production. Tapioca is a cassava meal commonly consumed in most part of the world and prepared from freshly harvested cassava tubers. The cassava tubers used for tapioca production are first boiled and sliced, before soaking in water overnight. The cassava tubers used for this study were harvested from the eastern farm of National Root Crops Research Institute, Umudike in Abia State, Nigeria. Some freshly harvested cassava tubers were subjected to 90 minutes cooking in clean water and at intervals of 15 minutes, samples were collected for starch and cyanide analyses. The result showed that increase in cooking time decreased the starch and cyanide contents of the cassava samples. Starch was reduced from 13.37% to 4.65% for every 2 g of starch tuber given 65.22% reduction after 90 minutes. The cyanide content was reduced from 36.65±0.16 to 2.49±0.08 mg/kg after 90 minutes of boiling, given a 93.2% reduction. The statistical analysis on the effect of cooking time on starch and cyanide contents showed significant mean difference (P < 0.0001) at both 5% and 1% levels of the various cooking time of the cassava. It is recommended that cassava used for tapioca production should be adequately cooked to reduce the cyanide content which could result in food poisoning.
Résumé
This investigation aimed at determining the cyanide and starch contents of different species of cassava grown in Abia State. Samples of cassava tubers were purchased from the local market and identified by a taxonomist from the National Root Crops Research Institute, Umudike, Abia State. In this study, the cyanide levels obtained were less than 100 mg/kg for both sweet and bitter cassava. The lower concentration of cyanide obtained from this survey, could have been influenced by the season of harvest (rainy season) in Nigeria. Of the six species analyzed, “0581” recorded the highest in cyanide content with 62.57 ± 0.10 mg/kg, followed by “30211” with 59.55 ± 0.19 mg/kg. Sweet cassava (0505) recorded the least with 36.65 ± 0.16 mg/kg cyanide. On the starch content, 21.70 ± 0.10% was obtained from “30572”, followed by “8083” with 20.62 ± 0.11% and “30211” had the least starch content with 17.48 ± 0.02%. Both Starch (%) and HCN (mg/kg) are statistically significant (p-value < 0.001) in the means for the various species of cassava under study. However, from the posthoc test, there is no significant difference between species 30211 and 0581. The other species are significantly different at 5% level. However, all the species of cassava tested had cyanide above the recommended level (10 mg/kg). Consumption of these cassava species unprocessed/inadequately processed would lead to serious health challenges and therefore, efforts are required to reduce cyanide content at least to the recommended level.