The nutrient composition, of Colocasia esculenta flowers (CF) and leaves (CL), and the green fruits of Solanum melongena (SM) were carried out as a means to determine their nutritional potential. Results showed that these food materials had high moisture and fiber levels which ranged between 888 and 906 g.kg-1; and 204 and 303 g.kg-1 dry weight (dw) for moisture and fiber respectively. The calorific values were between 3889 and 4001 kcals.kg-1 dw, while the total lipids ranged from 53 in CF to 71 g.kg-1 dw in SM. The leaves of Colocasia esculenta had the highest crude protein value of 307 g.kg-1 dw. The flowers had 149 g.kg-1 dw while SM had 138 g.kg-1 dw. The amino acid profile in the flowers and leaves of Colocasia esculenta in contrast to SM were balanced comparable to the reference FAO pattern. Ash values were high (ranging from 76 in SM to 98 g.kg-1 in CL) with potassium being the principal element. Iron and Zinc levels were also high especially in CF (with 303 and 82 mg.kg-1 dw respectively). These foods also contained moderate quantities of calcium, phosphorus and magnesium but were poor in manganese and copper.
Effect of squeeze‐washing, boiling in kanwa (a local alkaline salt) and drying of the leaves of some leafy vegetables (Vernonia colorata, V. calvoana var. bitter, V. calvoana var. nonbitter and V. amygdalina) consumed in Cameroon on antinutritional factors were evaluated. Results show that values for polyphenols were high in the unprocessed leaves. These values were reduced by 84.5% in V. amygdalina during processing. Sun drying and oven drying at 75C also caused slight losses (P < 0.05) in polyphenols. Saponin values were high in these four species but were considerably reduced by processing, rendering the nutrients in these leafy vegetables more bioavailable. Reductions (P < 0.05) were also observed for proteins as a consequence of processing by squeeze‐washing and use of kanwa. Similar trends were found for oxalic acids. Losses of up to 73% oxalic acids were observed in samples after processing. With the exception of drying, significant losses in minerals were observed due to these processes. This study, therefore, suggests the use of some of these different processing techniques to reduce the levels of antinutritional factors in these leafy vegetables.
PRACTICAL APPLICATIONS
The different species of leafy vegetables (Vernonia) are potentially rich sources of provitamin A, vitamin C and minerals. Use of appropriate processing and preservation technology makes these vegetables available at off seasons and in cities of high demand and improves on the actual nutritional value to the consumers. Industrially, these vegetables can be processed by squeeze‐washing and the use of minimal quantities of kanwa and possibly dried at 45C for use in urban centers.
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