Nutrient contents and thermal degradation of vitamins in organically grown fluted pumpkin (Telfairia occidentalis) leaves

The nutrient contents of a widely-consumed leafy vegetable produce – Telfairia occidentalis using poultry manure (PM) and mineral fertilizer (Nitrogen, phosphorus and potassium-NPK) application were evaluated for comparison. PM at four levels (0, 5, 10 and 15 tonnes) and a standard rate of 90kg NPK per hectare was applied. Leaves were harvested for immediate analyses at 15 weeks after planting to determine the proximate composition, elemental nutrient composition, water-soluble vitamins and anti-nutrient contents. Kinetics of vitamin degradation during drying of leaves at 50, 55 and 60oC and durations for 30 to 180 minutes was investigated. Data obtained showed that proximate composition was significantly affected by treatments (p<0.05) except crude protein. The values of elemental nutrient analysed were significantly different (p<0.05), except for potassium (K). Significant differences (p<0.05) due to fertilizer application observed for the water soluble vitamins except thiamine content. No significant difference (p>0.05) was observed in the anti-nutrient contents of the leaves. The percentage loss of the vitamins investigated revealed similar trends after drying for about 180 minutes with vitamin C having the highest values (29.35 to 37.07%); followed by thiamine (26.67 to 32.61%); and riboflavin (25.65 to 31.30%). Regression model was developed for retention of vitamins as a function of tonnage of PM, drying temperature and time with high values of R2 (0.901-0.951).