Nutritional value of wheat flour mixed with cassava leaf protein concentrate

Abstract

Non - conventional foods, as cassava leaf, with about 20% of protein in dry-weight, have been often used in the human diet as alternative foods. The use of cassava leaf as a concentrate enables the elimination of part of its residue and makes it easier to be added to conventional foods, such as cereals, improving their protein value. The aim of this study was to evaluate the protein quality of mixtures of wheat flour (WF) and cassava leaf protein concentrate (CLPC), on the levels of 5 and 10% of CLPC in WF. The CLPC was obtained by grinding the fresh leaves with NaOH 0.1 N, followed by filtration, precipitation of the protein in the “juice” by natural fermentation, homogenization of the precipitate and dehydration by spray-dryer. The composition of CLPC was determined (protein 36.36%, fibers 3.79%, lipids 12.26%, ashes 8.59% and carbohydrates 39%). The amino acid level showed a good profile, except for methionine which was limiting. A biological assay was carried out with rats to determine the protein quality of the mixture of CLPC and WF by Net Protein Ratio and its digestibility. Although the chemical score of WF has been improved by the addition of CLPC, the mixture remained limiting in lysine. There was no significant difference in the weight gain of the rats fed with wheat flour diets with or without the addition of CLPC, being all below the values obtained for casein diet. The Net Protein Ratio values were 2.03, 1.98, 2.15 and 4.61 for diets containing zero, 5 and 10% of CLPC and casein, respectively. There was a significant decrease on the digestibility of he diet with increasing addition of CLPC to WF, from 99.6% for the diet without addition to 96.6 % for the diet with 5% and 90.1% for the diet with 10% of CLPC, in relation to the casein diet. It was concluded that although the amino acid profile and the chemical score had suggested an improvement on protein quality of WF with 5 or 10% of CLPC, this was not observed on the biological assay. This can be due to the presence of antinutritional factors or to a low solubility of the protein, which could reduce the digestibility of CLPC.