Chemical composition and nutritional evaluation of a cowpea protein concentrate

Martin Alain Mune Mune^b*, Samuel René Minka^a, Israël Lape  Mbome^b

^a Department of Biochemistry, University of Yaounde I, PO Box 812 Yaounde, Cameroon

^b The Higher Institute of Sahel, The University of Maroua, PO Box 46 Maroua, Cameroon

^cFood and Nutrition Research Centre, PO Box 6163 Yaounde, Cameroon

Corresponding author Email: alainmune@yahoo.fr

Accepted 10 October 2012

Abstract

Cowpea protein concentrate was prepared by isoelectric precipitation, under optimum conditions determined in a previous study. The concentrate contained 86.90 % of the flour total protein, and had 85.82 % protein. Sugars and ash were in lower contents in the concentrate compared to the flour, while Fe and Zn contents were not significantly (p> 0.05) different. Phytates and polyphenols were eliminated in abundance during protein extraction and presence of trypsin and α-amylase inhibitors in the concentrate suggested application of an adequate heat treatment before its use in food products. The concentrate in vitro protein digestibility was high (86.81-88.74 %), and had a balanced essential amino acid composition compared to the FAO/WHO reference pattern. Tryptophan and total sulphur amino acids were first and second limiting amino acids. The predicted protein efficiency ratio, essential amino acids index and biological value indicated the good quality of cowpea protein concentrate, although elimination of tryptophan and sulphur-rich proteins during protein extraction affected the chemical score and protein digestibility corrected amino acid score.

Keywords: cowpea, protein concentrate, antinutritional factors, protein quality