Effect of Fermentation and Heat Treatment on the Nutrient and Antinutrient Composition of African Walnut (Tetracarpidium conophorum)

Abstract

Conophor plant (Tetracarpidium conophorum) is a tropical climbing shrub that belongs to the family Euphorbiaceae. It is one of the lesser known and underutilized oilseeds. Mature conophor nuts were processed in three ways namely cooking for 2 h, roasting in hot sand at 130°C for 1 h and natural open air fermentation for three days. Both raw and processed samples were dried and milled into flour for the determination of proximate and mineral composition and certain antinutrients. The raw nuts showed high content of protein and fat. Cooking and fermentation further significantly (p<0.05) improved the protein level. Fat was significantly (p>0.05) reduced by fermentation. Ash, crude fibre and carbohydrates were significantly (p<0.05) reduced by the three processing methods. Fermentation significantly (p<0.05) reduced all the minerals determined. However, Ca content was significantly increased (p<0.05) by cooking and roasting. The sodium: potassium ratio in the raw sample (1.02) was reduced by the three processing methods. The level of antinutrients were generally reduced by cooking and fermentation with the latter being more effective than the former in the case of alkaloid content. Roasting increased the tannin content. The study thus reveals cooking and fermentation as good methods of processing the conophor nut in order to harness its nutrient.