Comparative Evaluation of the Nutritive and Physico-Chemical Characteristics of the Leaves and Leaf Protein Concentrates from Two Edible Vegetables

摘要

The leaves and Leaf Protein Concentrates (LPCs) from two edible vegetable species; Amaranthus hybridus and Manihot esculenta were analysed for their chemical and physico-chemical characteristics. The LPCs were produced from these species using village-level, low-cost fractionation techniques. The leaves and their corresponding LPCs were subsequently characterized with respect to their proximate composition, mineral constituents, polyphenolic content and functional properties. On the average, the leaves contained 29.5 g 100 g 1 DM crude protein (range 28.0-30.9 g 100 g 1 DM) and 7.6 g 100 g 1 DM crude fibre (range, 6.4-9.0 g 100 g 1 DM). Gross energy averaged 459.0±22.6 kcal 100 g 1. The leaf protein extract on the average contained 38.5 g 100 g 1 DM crude protein (range, 35.2-41.7g 100 g 1 DM); 1.0±0.6 g 100 g 1 DM crude fibre; 7.7±2.0 g 100 g 1 DM fat; 6.9±1.8 g 100 g 1 DM ash and 554.5±113.8 kcal 100 g 1 gross energy. Ca, Mg, Na, K were most abundant minerals in the leaves and leaf protein concentrate while Cu and Zn were the least abundant. The polyphenols, as tannic equivalent, were reduced in the protein extracts. The Fat Absorption Capacity (FAC) varied from 16.7±1.2% in A. hybridus to 19.3±1.2% in M. esculenta while the Water Absorption Capacity (WAC) varied from 158.0±1.2% in M. esculenta to 226.7±% in A. hybridus with a CV of 25%. The emulsion capacity and stability were similar between the two species as indicated by the low Coefficients of Variation (CV) of 15.4 and 14.2%, respectively. The foaming capacity and stability did not also vary widely between the LPCs as indicated by low CVs. All the samples had varying solubilities with multiple maxima and minima with changes in pH. Based on the analytical data, the nutritional potentials of these underutilized protein resources were discussed and the need for their incorporation into low-Nitrogen foods was recommended.