ABSTRACT

The effect of processing methods on the nutrient content of three cultivars of bitter leaf were investigated. These cultivars: Vernonia corelata, Vernonia amygdaiina, Vernonia calvana were subjected to different analysis-proximate, mineral, anti-nutrients and amino acid profile. Results obtained shows that the protein content of the bitter leaf varied significantly (P< 0.05) in the fresh Vernonia plants from 9.56% (V. colerata) to 12.14% (V. Caliana). The crude fibre content and ash also varied from 11.14% to 16.10% and from 4.93% (V. Carenta to 6.22% (V. Calvana) respectively. Fat and moisture content varies similarly. The processing methods of blanching and abrasive washings reduced the proximate composition significantly. Moisture, protein, fat, fibre and ash were all reduced to an extent after processing but abrasive washing had higher effects on the blanching. Although there were variations in mineral content of the three Vernonia plants, all the plants had high mineral content with calcium ranging from 85.5 mg/bOg (V. coleratea) to 113.56mg/bOg. (V. Calvana) potassium content was between 316.67mg/bOg to 390.67mg/bOg and sodium content ranged from 36.6mg/100 (V. Calvana) tp 41.8mg/bOg (V. volerata). The trace element copper, zinc and iron were also detected but with lower concentrations. The potentials of the vegetable as good source of micro minerals was observed. However, the processing methods caused reduction in the mineral content of the plant leaves irrespective of the species involved. The result further showed varied concentration of the antinutrients alkaloid, saponin, phenols, oxalate, phytate, tannins etc. Most antinutrients were higher in V. amygdalina than the other two species with alkaloid 1.86%, saponin 2.43%, tannin 0.23%, phytate 0.545%, phenols 0.678%, oxalate 0.3 19% and anthocyanin 0.053%. The processing method of abrasion, blanching and, washing resulted in reduction in the antinutrient content of the leaves and this was needed as a positive impact on the nutrient status. It was also recorded that out of the nine essential amino acids, including lysine, histidine, threonine, isoleucine, leucine, phenyalanine, valine, tryetophan and methronine were present in the plant at different concentrations. However, the processing methods also lead to variations often reducing the amino acids when compared with the fresh sample. It was concluded that the Vernonia cultivars contained enough nutrients in terms of proximate, minerals and amino acid. The antinutrients were also reduced considerable by the processing method. It was recorded that the use of both processing methods should not be discouraged.