Effect of processing method on the antinutrient Content of Tacca leontopetaloides (L.) Kuntze flour
Résumé
Aims: This study was aimed at evaluating the effect of the method of processing on the antinutrient content of flours made from Tacca leontopetaloides (Tacca) tubers. Study Design: Two experimental designs - the randomized block and the doehlert designs - were used in the study. Place and Duration of Study: The study was carried out in the Laboratoire dingenierie et Biomolecules of the University of Lorraine, France between September 2011 and May 2012. Methodology: Fresh tacca tubers were peeled, sliced and subjected to six different soaking and boiling conditions: unprocessed, 36 h soaking- 4h boiling, 72h soaking, 4h boiling, 4h boiling-36 h soaking, 4h acid boiling, 4h alkaline boiling. Following the doehlert design, 9 treatments were obtained within the experimental domain of soaking (0 to 48h) and boiling time (3 to 5 h). The slices were dried and ground into flours which were subsequently analyzed for their antinutrients content. Results: The results revealed that untreated tacca flour contained high levels of antinutrients: total oxalates 870 mg/100g; soluble oxalates 399.7 mg/100g; phytates 458.0 mg/100g; cyanides 1.59 g/100g; saponins 4081.2 mg/100gDM; total polyphenols 419.3 mg/100g; total tannins 355.2 mg/100g; flavonoids 23.5 mg/100g and alkaloids 803.9 mg/100g. Soaking or boiling alone induced only limited reductions (up to 50% in most cases) in the antinutrients content of the flours. While boiling compared to one step soaking generally had a much higher impact on the reduction in antinutrients, a significant difference was observed amongst boiling solutions. In fact while boiling in water had a limited effect on the elimination of oxalate and saponins, boiling in alkaline was less efficient in the removal of alkaloids. Boiling followed by soaking was more effective in reducing antinutrients compared to boiling or soaking alone. Experiments carried out to optimize the treatment conditions showed 25 and 4-5 hours as the respective optimum conditions for soaking and boiling of the tubers to obtain flour of low antinutrient content. Conclusion: Soaking and/or boiling in solution leads to more than 50% reduction in the antinutrients contents of tacca. The most efficient treatment condition resulting in 90% reduction in all antinutrients consists of double soaking for periods of 36h each. The residual antinutrients are below non toxic levels, and might play positive roles in metabolism, but this is yet to be investigated.