Amino Acid Profiles, Total Nitrogen Contents, and Computed-Protein Efficiency Ratios of Manihot esculenta Root and Dioscorea rotundata Tuber Peels

Abstract

Tuberous roots of cassava and yam are major sources of dietary carbohydrate to human, alternative sources of energy in livestock feeds, and sources of starch in small-scale industries. Investigations on amino acid profiles, total nitrogen contents, and computed-protein efficiency ratios (C-PER) of tuberous root peels ofManihot esculentaCrantz andDioscorea rotundataPoir. were carried out. Amino acid analysis was carried out using ion-exchange chromatography methods. Total nitrogen content was measured using the micro-Kjeldahl methods. The C-PER was calculated using regression equation. The concentrations of amino acids detected in the cassava peels ranged from 0.54 to 6.54 g/100 g protein, whereas those of yam peels were between 0.37 and 6.25 g/100 g protein. The total amino acid concentration of the cassava peels was not significantly (p>0.05) higher than that of the yam peels. Essential amino acid scores showed that Phe + Tyr and Met + Cys were the most abundant and limiting amino acids, respectively, in cassava and yam peels. The percentage nitrogen content and C-PER of the cassava peels were significantly (p<0.05) higher than those of the yam peels. The cassava and yam peels were not sources of good quality proteins. Therefore, the use of cassava or yam peels as livestock feeds should be supplemented with other sources rich in good quality proteins.

Amino acid profile and scores of some selected traditional diets commonly consumed in northwest zone, Nigeria

“…The nutritional value of any protein is directly related to the amino acid composition. Dietary proteins in form of amino acids are needed for growth, metabolism, and body maintenance especially in the young individuals 1 . The amino acids contents of the prepared diets of the three states shows eighteen amino acids out of the common twenty amino acids found in proteins due to glutamine and asparagine which were respectively converted into glutamate and aspartate, hence the higher concentration of the later 1 .…”

“…This may be a reason that, in some of the state, especially Katsina state, where the most highly selected prepared diets (TMW SWKS and TMY SWKS) contain the higher EAA levels compared to moderately-and the least selected diets, since meat was used in preparing the kuka soup served with tuwo. The quality of the proteins can be determined in relation to the composition of a standard protein, which is recognized as the most relevant for the assessment of the protein quality in the nutrition of all population 1 . The Joint FAO/WHO/UNU Expert Consultation 12 has recommended that the composition of amino acids in local and regional diets should be taken into consideration to determine the chemical composition of diets and estimate of their protein quality.…”

“…The first limiting amino acids; lysine and SAA (Met + Cys) in the selected prepared diets play important role to human health. A reduced supply of lysine in the diet may lead to mental and physical retardation because it constitutes an essential precursor for the de novo synthesis of glutamate, the most significant neuron-transmitter in the mammalian central nervous system 1 . Methionine is the major donor of the methyl group to affect DNA and protein methylation in cells 14 .…”

“…Intakes of large amounts of amino acids can produce toxicities, in which plasma concentrations of the administered amino acid rise to very high levels. Elevated levels of amino acids and their products (e.g., ammonia, homocysteine, and asymmetric dimethylarginine) are risk factors for neurological disorders, oxidative stress, and cardiovascular disease 1 . Increased ammonia in the body is toxic and may lead to brain malfunction and coma.…”

“…The nutritional value of any protein is directly related to the amino acid composition. Dietary proteins in form of amino acids are needed for growth, metabolism, and maintenance of the body especially in young ones 1 . Differences in protein value of human diets are in protein quality, not quantity.…”