Effect of cooking methods on the micronutrient profile of selected vegetables: okra fruit (<i>Abelmoshcus esculentus</i>), fluted pumpkin (<i>Telfairia occidentalis</i>), African spinach (<i>Amarantus viridis</i>), and scent leaf (<i>Ocumum gratissimum</)

Abstract

Introduction: Many vegetables are usually cooked before consumption though their vitamin and mineral levels tend to decrease in the process.

Objective: This study evaluated the vitamin and mineral profiles of four vegetables subjected to steaming and boiling.

Methods: Freshly purchased vegetables were washed and divided into three portions. The first was pulverised raw while the second and third were pulverised after boiling and steaming respectively. The pulverized samples were chemical analysed using standard procedures. Data obtained were statistically analysed using Analysis of variance (ANOVA). Duncan's multiple range test was used to compare the means. Significance was accepted at (p ≤ 0.05).

Result: Micro nutrient content of the vegetables were significantly higher (p ≤ 0.05) in the raw than the steamed and boiled samples. No significance difference (p ≤ 0.05) was observed in the vitamin B₁ (0.12- 1 0.14mg) and iron (1.06-1.11mg) contents of boiled and steamed fluted pumpkin as well as in the vitamin B₂ (0.23-0.27mg) and zinc (0.17mg) contents of African spinach. The vitamin B₆ content of the boiled and 6 steamed vegetables were not significant (p ≤ 0.05) except for that of okro fruit. Vitamin B₂ (0.20-0.24mg),  vitamin B₁₂ (0.01-0.02mg) and potassium (1.61-1.71mg) content of fluted pumpkin and phosphorus content (23.38-26.97mg) of African spinach were statistically similar irrespective of treatments while ascorbic acids and zinc (fluted pumpkin), total folate, sodium, calcium, iron (African spinach) and vitamin B₁ (scent leaves) were significantly affected by boiling.

Conclusion: Steamed samples had better micro nutrient retention than the boiled. In the combat against micro nutrient deficiency, steaming rather than boiling of vegetables should be advocated.

Keywords: Vegetables, vitamins, mineral, boiling, steaming