EFFECT OF POPPING ON THE NUTRIENT, ANTI- NUTRIENT AND THE STARCH DIGESTIBILITY OF DIFFERENT VARIETIES OFMAIZE (Zea mays)

Abstract

Popped and un-popped grains of four varieties of maize namely Africana popcorn, (A1 and A2), T.Z.E COM5 (B1 and B2), BR9928 DMR- SR-Y (C1 and C2), and DMR-ESR-Y (D1 and D2) were analyzed for their proximate composition, energy, mineral content, functional properties, anti- nutrients, anti-oxidant properties, amino acid profile, vitamins, functional groups using fourier transformed infra red spectroscopy (FTIR) as well as the in-vitro starch digestibility using α amylase enzyme. The samples were later used to formulate eight (8) different fish diets and the physical characteristics of the fish diets determined. The un-popped Africana popcorn had the highest moisture content 10.90±0.08g/100g while the lowest 1.04±0.00g/100g was in popped DMR-ESR-Y. Highest value of crude protein (CP) 12.01±0.01g/100g was in popped DMR-ESR-Y while un-popped BR9928 DMR-SR-Y had the lowest value 0.81±0.01g/100g. Crude fibre (CF) was highest in popped Africana popcorn 6.26±0.01g/100g and the lowest value 2.42±0.01g/100g was in un-popped T.Z.E COM 5. Ethyl extract (EE) ranged from 3.42±0.00g/100g in popped BR9928 DMR-SR-Y to 10.27±0.03g/100g in un-popped Africana popcorn. Total ash ranged from 2.42±0.01g/100g in un-popped T.Z.E COM 5 to 6.15±0.02g/100g in popped DMR-ESR-Y. Nitrogen free extract (NFE) was highest (81.55±0.17g/100g in popped BR9928 DMR- SR-Y and lowest value (73.18±2.10g/100g) was found in un-popped Africana popcorn. The gross energy ranged from 304.68±0.05Kcal/100g in popped T.Z.E COM 5 to 432.16±0.02Kcal/100g in un-popped DMR-ESR-Y. Of all the minerals analyzed, Na, K,Mg,Ca and P were the most abundant while Pb was below detection level in all the samples. Popping increased mineral content in Africana popcorn except in Fe but variation was found in all the other samples. There were significant difference (P˂0.05) in all the parameters determined under functional properties most especially water absorption capacity (WAC) oil absorption capacity (OAC) and foaming capacity (FC). All the samples analyzed showed increase in protein solubility at the higher pH range (pH 8-12). Results on anti-nutrients showed that phytates, phytic acids, oxalates, tannins and phenolic compounds were drastically reduced after popping. Similarly, anti-oxidant properties namely 1,1-diphenyl-2 picrilhydrazy(DPPH), free radical ferric reducing anti-oxidant property (FRAP) and Fe2+ chelating assay were drastically reduced after popping. The essential and non-essential amino acids of the samples were highly reduced after popping, most especially methionine, glycine, tyrexine, valine, protine, phenylamine, argine and iso-leucine in all the samples analyzed except glutamic acid in Africana popcorn which had 81.11mg/g in un-popped and 90.56mg/g in popped sample. Data on vitamins (A, B1,B2,B3,D and E) content showed reduction in all the samples after popping with exception in vitamin A content in un-popped T.Z.E COM 5 (142.52mg/g) and popped (215.65mg/g). The same trend were observed in BR9928 DMR-SR-Y un-popped (1.00mg/g) and popped (1.15mg/g) and DMR-ESR-Y un-popped (0.90mg/g) and popped (1.16mg/g). FTIR analysis showed that OH stretch, CH, C=C, C-C, C-O and C-N stretch were common to all samples analyzed except the presence of C-H bend in un-popped Africana popcorn and disappearance of C-N stretch in popped BR9928 DMR-SR-Y and DMR-ESR-Y and a presence of C=O stretch. The result on invitro starch digestibility revealed that high level of glucose was produced after digestion of the starch with α amylase enzyme. The results on the physical characteristics of all the diets showed that there were no significant difference (p˃0.05) except in DMR-ESR-Y which had the highest floatability time of 1.87sec and 1.86sec for poped and un-popped respectively. Generally, the statistical analysis showed that popping had effect on most of the parameters analyzed.