Effects of Age at Harvest on the Nutritional Compositions of (Jute) Corchorus Oltorius L. (Ewedu)

Abstract

Corchorus olitorius L. (Jute) is one of the leafy vegetables commonly consumed in Africa, it is a native plant of tropical Africa and Asia, and it is popularly used in soup preparation and folk medicine for the treatment of fever, chronic cystitis, cold and tumours. This research was conducted to determine the effects of maturity on the minerals, antioxidants, and anti-nutrient compositions of Corchorus olitorius leaves. The experiment was conducted at the Oke Ogun Polytechnic Saki by cultivating a garden for the leafy vegetables. It was planted in July and harvesting was done at three harvesting ages: 5, 7 and 9 weeks. Laboratory analysis was done on the air-dried edible portions using standard analytical methods. The highest values obtained for K, Na, Fe, Mg and Ca were 222.85mg/L at 5 WAS, 27.97mg/L at 5 WAS, 7.11mg/L at 9 WAS, 93.33mg/L at 9 WAS and 37.33mg/L at 9 WAS respectively. Only Na and K decreased with plant age at harvest while other minerals increased progressively. The antioxidant (total phenolic, flavonoid, vitamin A, E and B₂) level increased progressively with plant age (0.08 ± 1.0 – 4.09 ± 1.0mg/g) with flavonoid having the highest value (4.09mg/g at 7 WAS) and both vitamin E and B₂ possessed the lowest value (0.08mg/g at 5 WAS). The anti-nutrient concentrations of the leaves (mg/g) of dry matter shows the range of 0.19 ± 0.1 mg/g (as for tannin at 5WAS) – 5.25 ± 1.0 mg/g (as for phytate at 7WAS) with less significant differences anti-nutrient levels observed at different age at harvest. It was therefore concluded that plant age at harvest had a greater impact on the proximate, mineral and antioxidant compositions of Corchorus olitorius (jute) with no significant impact on the anti-nutrient levels.