PERFORMANCE EVALUATION AND PRODUCT CHARACTERIZATION OF MAIZE(ZEA MAYS L) FLOUR MILL

Abstract

Maize flour has a higher percentage of whole grains (4.5 percent) compared with wheat flour. The fibre content is also much higher, as in the amount of vitamin B. In some developing countries like Nigeria, a few commercial maize processing mills are in operation. Local production has to be geared up to meet the demand. This research work studied the performance of a locally fabricated dryer-cum-roaster and hammer mill and evaluates the chemical analysis of products obtained. Selected physical and mechanical properties of ART/98/SW5-OB-W, ART/98/SW1 and Swan 1 SR Y varieties of maize were determined. These include moisture content, tri-axial dimensions, effective diameter, sphericity, bulk and true densities, porosity, mass of a thousand (1000) seed, angle of repose and coefficients of static friction, dynamic friction and compressive strength. Maize samples were passed through the hopper into the roaster and exit after roasting, thereafter milled in the hammer mill and sieved. Each experiment was replicated five times for a chosen speed (6.6, 12.8, 19, 24 and 30 rpm), moisture content (20, 15.8 and 9.5% wet basis) and temperature (70, 100 and 150oC). Response Surface Methodology (RMS) in the design expert software version 8.0.7.1 was used to evaluate the effect of the factors on the evaluation parameters. The product classification of material was done using Ro-tap sieve shaker. Products obtained were analyzed chemically. Descriptive statistics of the mean and standard deviations of the parameters of engineering properties and nutritional compositions were estimated with Analysis of variance and Least Significant Difference. The mean values for length, width, thickness and effective diameter for ART/98/SW06- OB-W,ART/98/SW1 and Suwan-1-SR-Ywere 9.55 mm, 7.89 mm, 4.34 mm and 6.84 mm; 8.57 mm, 7.91 mm, 4.26 mm and 6.56 mm; and 9.99 mm, 7.97 mm, 4.60 mm and 7.13 mm respectively. Angle of repose reduces along with varieties from ART/98/SW06-OB-W vii (43.76o), ART/98/SW1 (43.07o) to Suwan-1-SR-Y (42.04o). There were significant differences in coefficient of friction on all the surfaces for the three varieties (p < 0.05). The maximum roasting capacity, roasting efficiency, conveyance efficiency and mechanical damage were 3.56 kg/h, 92.97%, 99.56% and 26.72% respectively. The response plots show that conveyor speed, moisture content and temperature had significant effects on all the evaluation parameters with high R2 (ranging from 0.74 to 0.89) for roasting efficiency and mechanical damage. The optimal predicted values for milling efficiency (82.60%, 91.24% and 92.46%) were obtained for ART/98/SW06-OB-W,ART/98/SW1 and Suwan-1-SR-Yvarieties respectively at a speed of 1700 rpm and moisture content 11.5% wet basis (standard errors 7.43, 4.86 and 3.02 at p < 0.05).The average particle size of comminuted mass maize product increased with machine speed and moisture content. The results of proximate analysis show that there were high significant differences (p < 0.05) among the mean values of the proximate and mineral compositions that were examined for all the varieties. The study had provided relevant data required for the design of processing equipment for the three varieties of maize. The evaluation parameters could be determined from the model equations developed. Among the three varieties of maize under investigation, Suwan-1-SR-Y gave the highest flour yield. From this study, products which are very useful in the production of aadun, dankwa and kokoro were obtained from maize