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

Paul Chidoka Chikezie,Odinakachi Stella Monago,Chiedozie Onyejiaka Ibegbulem,Ferdinand Nkem Mbagwu,Chibuike Udodi Nwachukwu

doi:10.1155/2016/1697458

Paul Chidoka Chikezie, Odinakachi Stella Monago + Show 3 more

Open Access

https://doi.org/10.1155/2016/1697458

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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 of Manihot esculenta Crantz and Dioscorea rotundata Poir. 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.

Highlights

L-α-Amino acids are the primary sources of nitrogen atom for biological systems
The concentrations of the various 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 (Table 1)
The findings of the present study did not qualify proteins from cassava and yam peels to be of good quality by virtue of their CPER indices

Summary

Introduction

L-α-Amino acids are the primary sources of nitrogen atom for biological systems. They are precursors for the biosynthesis of nitrogenous compounds such as haem, purines, urea, pyrimidines, hormones, neurotransmitters, biological active peptides, and proteins [1, 2]. Diets for human and livestock must contain adequate quantities of these nutritionally essential amino acids, whereas the remaining nutritionally nonessential amino acids are readily biosynthesized from metabolic pathways involving amphibolic intermediates [2]. Amino acids such as Leu, Ile, Trp, Lys, Phe, and Tyr are termed ketogenic because they are precursors for the synthesize ketone bodies, namely, acetone, acetoacetate, and βhydroxybutyrate, while Arg, Gln, His, Pro, Ile, Met, Thr, Val, Phe, Tyr, Asp, Asn, Ala, Cys, Gly, Ser, and Trp are termed glucogenic because they can be metabolized to glucose and glycogen. Ile, Trp, Tyr, and Phe are both ketogenic and glucogenic, whereas Lys and Leu are strictly ketogenic [4]

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