Effect of Different Processing Methods on the Anti-nutritive Components of Selected Indigenous Vegetables

Indigenous vegetables are widely utilized due to their high nutritional profiles, easy availability, and accessibility in rural areas. The consumption of indigenous vegetables is limited by their high perishability nature which causes high post-harvest losses. Also, the presence of anti-nutritive components which tend to affect the bioavailability of micronutrients, poses a challenge in availing their full nutritional potential to consumers. This study aimed to determine the effect of boiling, fermentation, solar and sun drying (with and without blanching) on the anti-nutritive components of the leaves of Cassava (Manhot esculenta Crantz), Black jack (Bidens pilosa) and Bitter lettuce (Launaea cornuta). The raw, dried, boiled and fermented vegetables were evaluated directly after being subjected to their corresponding treatments. Total oxalate and hydrogen cyanide (HCN) were analyzed using titrimetric methods and phytate was determined using the UV spectrophotometric method. From the results, oxalic acid ranged from 180.2 ± 1.56 to 26.3 ± 2.34mg/100g, phytate ranged from 18.8 ± 1.07 to 0.7 ± 1.11mg/100g and hydrogen cyanide ranged from 357.1 ± 10.56 to 4.1 ± 2.49mg /100g across the treatments. All processing methods significantly (P<0.05) reduced hydrogen cyanide and oxalic acid content in all vegetable samples. Phytate was significantly reduced (P<0.05) after boiling and fermentation while, all drying treatments resulted in non-significant changes in phytate content. In consequence, all processing methods studied proved to be effective in the reduction of hydrogen cyanide and oxalic acid. Boiling and fermentation showed their effectiveness in the reduction of phytate. Therefore, it is recommended that these plants should be eaten boiled or fermented to increase the bioavailability of micronutrients.