Effects of processing on amino acids composition of Leucaena leucocephala (Lam De Wit) leaf meal

Abstract

The high cost of animal protein sources has made it necessary to evaluate the use of alternative plant protein sources especially unconventional plant proteins. Leucaena leucocephala (white lead tree) is a leguminous plant, the leaves of which have the potential of being used as a plant protein source. Leucaena leaf has been analysed to have a crude protein value of 15.2-34.3%. The plant leaves were collected from the forage section of the College of Agriculture and Animal Sciences (CAAS) Mando, Kaduna. The first group of the leaves was divided into three and sun-dried for 24 hours, 48 hours and 72 hours respectively. The second group was further divided into three subgroups which were soaked in water for 24 hours, 48 hours and 72 hours then sun-dried. The two groups of the leaves were ground into leaf powder. The effects of sun-drying and soaking on amino acid composition of L. leucocephala leaves was investigated. The amino acid analysis was done by ion-exchange chromatography (IEC) using the Technicon Sequential Multisample Amino Acid Analyser (TSM) Technicon Instruments Corporation, New York. The essential amino acids detected in L. leucocephala leaf were arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine. Alanine, cysteine, tyrosine, aspartic acid, glutamic acid, glycine, serine and proline were the non-essential amino acids detected. Sun-drying and soaking led to significant (P≤0.05) losses in the concentration of all the amino acids in the leaf samples (Sundried for 24 hours - SD1, Sundried for 48 hours - SD2, Sundried for 72 hours - SD3, soaked in water for 24 hours – SW1, soaked in water for 48 hours - SW2, soaked in water for 72 hours - SW3) when compared with the raw leaf samples (SU). Soaking caused higher reduction in the amino acid levels when compared to sun-drying in the test leaf meals which was significant at P≤0.05. The amino acid scores revealed that lysine and methionine were the limiting amino acids in L. leucocephala leaves relative to WHO/FAO/UNU standard for preschool aged children. Therefore, processed L. leucocephala leaves should be supplemented with other feed ingredients rich in these amino acids for animal feed production.

Keywords: Leucaena leucocephala leaf, sun-drying, soaking, amino acid composition.