Nutritional potentials of some tropical vegetable leaf meals: chemical characterization and functional properties

Abstract

Three tropical vegetable species (Talium triangulare, Amaranthus cruentus and Telfairia occidentalis) were selected based on their availability and agronomic desirability. The freshly harvested vegetable leaves were subjected to 2 processing techniques (shredding and sundrying) before milling into the vegetable leaf meals (VLMs). The crude protein ranged from 19.9+1.8 to 35.1+1.7. The crude fibre ranged from 8.8+3.1 to 12.7+4.2. Ether extract (fat) had a wide range of 5.4+3.2 to 29.2+2.1. Ash contents had a range of 10.9+6.2 to 19.4+3.0. The nitrogen free extract ranged from 19.7+0.3 to as high as 43.5+0.7. Gross energy values had a range of 251.5MJKg-1 to 383.2MJKg-1. The mineral contents of the air-dried VLMs indicated that Ca, Mg, Na, K are the most abundant minerals with values as high as 2.0, 2.5, 7.1 and 4.8gkg-1DM for Ca, Mg, Na and K respectively in some samples analysed. The amino acid profiles of the VLMs indicated favourable nutritional balance except for lysine and methinone which appear marginal. The Water Absorption Capacity (WAC), Fat Absorption Capacity (FAC), Fat Emulsion Capacity (FEC) and Emulsion Stability (ES) were similar for the 3 VLMs. The values obtained for Foaming Capacity, Least Gelation Concentration and Foaming Stability after 30 minutes for the 3 VLMs were also similar. The protein solubility curves of all VLMs were similar at both alkaline and acid media with minimum solubility (isoelectric point) at between pH 4 and 5 for the VLMs.

Keywords: Vegetable leaf meals, nutritional potentials, amino acid profile