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Influence of heat processing on the nutrient composition of vegetable leaves consumed in Nigeria

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Abstract

The effect of cooking on the proximate composition, energy value, ascorbic acid content and selected mineral levels of six edible vegetable leaves used in the preparation of Nigerian diets was investigated. In raw samples, moisture content ranged from 70.69 ± 8 0.15% in hard leaf (HL) to 93.29 ± 0.11% in water leaf (WL). Fluted pumpkin leaf (FPL) had the highest ash content of 5.91 ± 0.05% followed by HL (3.20 ± 0.33%); ash was lowest (1.22 ± 0.07%) in water leaf (WL). Protein was highest (5.3 2 ± 0.05%) in green leaf (GL) followed by HL (4.87 ± 0.08%) then BL (4.40 ± 0.24%) and was lowest in WL (1.68 ± 0.31%). For crude fat, the order was Oha leaf (OL) > FPL > GL > BL > WL > HL. Total carbohydrate was low in all the samples and was lowest in WL (3.09 ± 0.31%) with the highest value of 20.85 ± 0.24% in HL. The low caloric values in raw samples, which ranged from 25.6 in WL to 106.4 kcal/100 g sample in HL, indicate that these edible leaves are not good sources of crude fat, crude protein and total carbohydrate. Heat processing did not significantly (p > 0.05) affect moisture content but generally decreased ash, crude protein and crude fat though the decrease was not significant. Cooking decreased the ascorbic acid content of all the edible leafy vegetables investigated. Loss in ascorbic acid to the cooking water ranged from 7.61% in HL to 96.0% in BL. Results indicate that the vegetables analyzed were good sources of sodium, magnesium, iron, zinc and copper. Cooking decreased the level of the divalent minerals Mg, Fe, Zn and Cu but increased that of the monovalent metal Na in all the edible leafy vegetables investigated.

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Authors and Affiliations

  1. Department of Biochemistry, Nutrition and Toxicology Unit, Faculty of Science, University of Port Harcourt, PMB 5323, Port Harcourt, Nigeria

    Eugene N. Onyeike, Alexius C. Ihugba & Chinyere George

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  1. Eugene N. Onyeike
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  2. Alexius C. Ihugba
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  3. Chinyere George
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Onyeike, E.N., Ihugba, A.C. & George, C. Influence of heat processing on the nutrient composition of vegetable leaves consumed in Nigeria. Plant Foods Hum Nutr 58, 1–11 (2003). https://doi.org/10.1023/B:QUAL.0000040327.57587.db

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