Effect of a typical rural processing method on the proximate composition and amino acid profile of bush mango seeds (<i>Irvingia gabonensis</i>)

Abstract

Various researchers have confirmed the view that forest and wood lands, among other natural boundaries in West Africa supply a massive amount of protein and carbohydrates to the citizens; however industrialization and urbanization has  threaten many of the food species from these ecosystems. For instance Itugha known to be highly prized and delicious indigenous food is getting extinct and the possibility of it’s origin and composition being lost in antiquity is high, more so data on nutrient composition of processed lrvingia products is limited. Samples of Itugha were prepared as it is obtained in the local setting. These and fresh seeds from the same source of fruits were subjected to proximate analysis and amino acid profile determination. The synergistic effect of pounding and fermentation (two rural processing methods) on proximate composition and amino acid profile of Irvingia gabonensis seeds were evaluated. Proximate analysis differed significantly (p > 0.05) between the processed product and fresh Irvingia seeds in crude protein, fat, ash and dietary fiber contents. Protein value was 19.4+ 0.4% dry matter (DM) for the product, 7.6 + 0.8 of (DM) for fresh seed of var gabonensis, Crude fat 66.60+ 0.80% DM seed and 58.00+ 1.0% product; ash 9.50+ 0.30% DM seed and 11.60 + 0.6% DM product. Dietary fibre was 18.20+ 1.80% DM seed and 12.30+2.00% DM product. Percent sucrose in starch was 2.10 + 3.50% DM seed and 9.60+ 3.10% DM product. There were significant losses in fat, dietary fibre, moisture and carbohydrate due to processing. High moisture level in seed 5.20 +0.6% DM  compared with product 2.10+ 0.8% DM is indicative of the presence of appreciable quantity of trapped water in the matrices of fresh Irvingia seeds which was favourable for fermentation. Amino acid profile showed significant differences (p < 0.05) in their levels in the seeds and the product. All the essential amino acids (EAA) were quantified with Leucine recording the highest value. In all, eighteen amino acids were quantified in both the fresh seed and processed product. They are Leucine 8.30+ 0.11g/16g Nitrogen (N) product and 7.60 + 0.12g/16gN seed, isoleucine 3.20+ 0.04g/16gN seed and 4.50+ 0.1g/16gN product; threonine 2.20+ 0.30g/16gN seed and 3.10+ 0.1g/16gN product, glutamic acid 13.40+  0.11g/16gN seed and 15.20 + 0.10g/16gN product. These recorded increases. Serine 3.10+ 0.04g/16gN seed and 2.80+ 0.01g/16gN product was the only amino acid that recorded a decrease in level due to processing. Other amino acids were methionine, tryptophan, valine, phenylalanine, histidine, aspartic acid, cystine, proline, glycerine, alanine, tyrosine, lysine and arginine. Processing method resulted in slightly higher levels of essential nutrients in the product than the seeds. Further investigation to determine the micoflora involved in the fermentation is recommended. It would also be necessary to isolate and identify the food  enzymes in the endosperm of Irvingia gabonensis. It has been observed that  nutrient dense plant foodstuff are facing extinction due to urbanization and  increased patronage of fast foods, as such, there  is need to increase available information on their nutritive potentials to encourage utilization.

Keywords: Pounding, Fermentation, Amino acids, Proximate, Irvingia .