Chemical composition and functional properties of leaf protein concentrates of Amaranthus hybridus and Telfairia occidentalis

Abstract

The proximate, mineral and amino acid compositions and functional properties of leaf protein concentrates of Amaranthus hybridus and Telfairia occidentalis were investigated on dry weight basis. The proximate values were high in ash, protein and metabolizable energy with respective values in A. hybridus as 17.2, 34.8 (g/100 g) and 1.4 MJ and in T. occidentalis 12.3, 35.4 (g/100 g) and 1.6 MJ; with rxy of 0.67 and Rc of 1.15. Minerals only slightly high in the samples were Na, Ca and P with values of 32.2, 50.2 and 45.7 (mg/100 g) respectively in A. hybridus and 31.2, 51.3 and 39.5 respectively in T. occidentalis; with rxy of 0.61 and Rc of 0.97. The amino acids were generally more concentrated in the A. hybridus than T. occidentalis with an rxy of 0.66 and Rc of 1.02. Total amino acid in A. hybridus was 678.1mg/g crude protein with total essential amino acid of 393.5 mg/g or 58.0 % while the total amino acid in T. occidentalis was 455.3 mg/g with total essential amino acid of 256.1 mg/g or 56.3 % showing both proteins to be high in essential amino acids. Threonine was the limiting amino acid in both samples with 0.69 (A. hybridus) and 0.43 (T. occidentalis). The functional properties showed that both have high water and oil absorption capacities with values of 230.0 and 182.9 % (A. hybridus), 95.0 and 146.3 % (T. occidentalis) respectively. While foaming capacity was low, foaming stability was high with a low rate of change (2.0 % /min) in A. hybridus and 1.7 %/min in T. occidentalis. The protein solubility was moderate with a range of 34.6-42.7 % with rxy of 0.77 and Rc 1.06. While experimental pI was pH 5.0 in A. hybridus and pH 4.0 in T. occidentalis; the theoretical pI in A. hybridus was 4.2 and 2.8 in T. occidentalis.