(OR03-07-24) Effect of Cultivar and Time of Harvesting on the Nutritional and Antinutritional Composition of the Leaves of Jute Mallow (Corchorus olitorius)

Objectives: To evaluate the nutritional and antinutritional contents of the tender leaves of Corchorus olitorius at flowering/fruiting stages and compare them with nutrients and antinutrients of the leaves at the vegetative stage.

Methods: Two Corchorus olitorius cultivars (Co-Ekiti and Co-Lagos) were organically produced at the agronomic evaluation field near the Federal University Oye-Ekiti (FUOYE) Ikole Campus Gate. The tender leaves of the two cultivars were harvested at the four (4), ten (10) and 12 weeks after planting (WAP). Four to six WAP (vegetative stage) is considered the best time by the farmers and consumers for harvesting and consumption of the leaves for optimum nutrition. The leaves are usually abandoned on the field by farmers after 6 WAP (flowering bud initiation and fruiting stages). The tender leaves of the cultivar were harvested 10 and 12 WAP from (where the youngest leaves were found) 20 cm to the apex of the branches of the Corchorus plants. The collected samples were oven-dried and analyzed at the Analytical Laboratory of the Faculty of Agriculture, FUOYE. The proximate composition and minerals were analyzed according to AOAC (2005) while the antinutrients were analyzed according to AOAC (2005), Amorim et al. (2008) and Abulude et al. (2003). Data obtained were analyzed using the R statistical software.

Results: The proximate parameters of the two cultivars did not vary significantly (P>0.05) except in moisture that significant differences (P <0.05) were observed in the cultivars. Crude protein was in the range of 21.55-22.85%; crude fibre 6.88-7.68%; ash 10.96-11.105%; crude fat 5.04-5.05%; carbohydrate 40.50-41.91% and moisture 12.95-13.63%. Crude protein was higher in the leaves at 10 and 12 WAP. The crude fat was lowest at 12 WAP. The carbohydrate and moisture contents of the leaves were statistically similar at all the harvesting times. There were no significant differences in the mineral contents of the leaves of the two Corchorus cultivars. Potassium (K) was in the range of 1182.33-1191.67 (mg/100 g); manganese (Mn) 379.12-383.53 (mg/100 g); zinc (Zn) 12.94-13.34 (mg/100 g); iron (Fe) 19.04-22.51 (mg/100 g); Magnesium (Mg) 12.64-13.13 (mg/100 g); copper (Cu) 1.58-1.94 (mg/100 g) and Sodium (Na) 47.84-51.14 (mg/100 g). The minerals Zn and Cu were higher in the Corchorus leaves at 10 and 12 WAP while the concentrations of K, Fe and Mg were slightly higher at 4 WAP. The leaves of Co-Ekiti and Co-Lagos were similar in their phytate, phenolic compounds and oxalate contents. Co-Lagos was significantly higher in saponin content. The phytate was in the range of 20.88-22.25 (mg/100 g), phenolic compounds 1253.80-1259.28 (mg/100 g); oxalate 5.46-6.82 (mg/100 g); saponin 9.19-10.23 (mg/100 g). There were no significant differences in the phenolic compounds and saponin contents of the leaves at 4, 10 and 12 WAP. Phytate and oxalate were similar at 4 and 10 WAP. Phenolic compounds were numerically lowest in the leaves of the Corchorus cultivars at 12 WAP.

Conclusions: The tender leaves of Corchorus olitorius harvested at 10 and 12 WAP were nutrient-dense and were nutritionally and anti-nutritionally comparable to the nutrient quality and antinutrients of the leaves at 4 WAP (considered the best time of harvesting for optimum nutritional quality). The crude protein, crude fibre and some of the minerals were higher at 10 and 12 WAP. The nutrient-density of the tender Corchorus leaves at 10 and 12 WAP should therefore be explored for human nutrition by the consumers, farmers and especially the women that grow them.

Funding Sources: This research was self-funded by the authors.