Vitamins and Minerals Composition of Eggplant (Solanum macrocarpon) and ‘Ukazi’ (Gnetum africanum) Leaves as Affected by Boiling and Steaming

Abstract

Aims: In relation to nutrient retention, cooking method is not a major factor considered when preparing vegetables at household level. The study evaluated the vitamin and mineral compositions of raw, boiled and steamed egg plant (Solanum macrocarpon) and ‘ukazi’ (Gnetum africanum) leaves. Methodology: 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. Their micro nutrients profiles were chemically determined using standard procedures. Data obtained was statistically analysed using Statistical Product for Service Solution (SPSS) version 21.0 for descriptive statistics such as means and standard deviation. Significance was accepted at p ≤ 0.05. Results: Micro nutrients content of eggplant were significantly (p ≤ 0.05) higher in the raw than the steamed and boiled samples. However, no significant (p ≤ 0.05) difference was observed in the vitamin B1 content of boiled (0.19 mg/100 g) and steamed (0.16 mg/100 g) samples. Except for vitamin B6, all the B-vitamins values of the raw and steamed ‘ukazi’ leaves were statistically similar. There was no significant difference in the beta carotene values of raw (587 mg/100 g), boiled (549 mg/100 g) and steamed (574 mg/100 g) samples. Mineral values of the three ‘ukazi’ samples were all significantly different (p=.05) and ranged from 0.28-181 mg/100 g in the raw, to 0.10-161 mg/100 g and 0.26-180 mg/100 g in the boiled and steamed samples, respectively. Conclusion: Steaming had better micro nutrient retention than boiling. Boiling and steaming the vegetables whole (without slicing) also enhanced their nutrient retention. To improve on the intake of micro nutrients, steaming whole vegetables rather than boiling them should be advocated.