Abstract-

Socio-economic relevance of fermented food in developing countries is evident. However, the production of this category of food is still achieved under primitive conditions. Ogi a fermented product from maize, sorghum or millet is usually transformed into gruel or porridge when heated. About a quarter of Nigeria population is said to consume Ogi on a weekly bases. This coupled with increasing industrialization and urbanisation in the country may however dictate the need for large-scale production of Ogi. The proposal for industrialisation of this process will lead to a deliberate and calculated combination of chemical or mechanical steps to aid the manufacture of this product. However, the growth of small-scale or large industries for this product may be confronted with some limiting factors prevalent in most third world countries. Ogi production have some similarities in unit operations when compared with corn starch production, therefore the same technologies may be adopted with appropriate modification in the production of Ogi and this will provide employment to a number of people. This review is with a view to establish the need to mechanise the process and as well as point out the technological and economical implication.

This study was undertaken to investigate the drying characteristics of red and white varieties of onion (Allium cepa) in a convective dryer. The drying characteristics of onion slices were examined at air temperatures of 50˚C, 60˚C and 70˚C and sample thicknesses of 2 mm. During the drying experiments, air velocity was held stable at 0.9 m/s. The effects of air temperature on the drying characteristics and quality parameters such as vitamins C and D, macro minerals (Mg, Na, P, Ca and K), non-enzymatic browning and thiolsulphinate of the dried onion slices were determined. For each of the plots of the drying curves from the mechanical drying tests, there was an absence of or just a very brief appearance of a constant rate period because onions are hygroscopic and hygroscopic foods tending to quickly enter the falling rate period; drying time decreased considerably with increased temperature. The time required to reduce the moisture content to any given value was dependent on the drying conditions, being the longest at an air temperature of 50˚C, 0.9 m/s and the shortest at an air temperature of 70˚C and air velocity of 0.9 m/s. The loss of vitamin C, which is a thermo-sensitive compound, was the least at an air temperature of 50˚C.

The effect of moisture content on some physical and mechanical properties of two varieties of tigernuts (Cyperus esculentus) was investigated. These properties include: geometric dimensions, linear dimensions, 1000 tuber weight, bulk density, tuber size, sphericity, angle of repose, porosity, coefficient of static friction and compressive strength. The moisture content levels used were 20, 25, 30, 35 and 40% wet basis (wb), and the two tigernut varieties used were yellow and brown types. The linear dimension, geometric diameter, sphericity, 1000-tuber weight, bulk density and angle of repose in both varieties increased with increasing moisture content. The average length, width and thickness of the yellow variety increases more than the brown variety at the determined moisture contents. True density of the yellow variety increased while the brown variety decreased with increase in moisture content. The porosity of the yellow variety reduces with increase in moisture content from 45.95 at 20% mc to 42.4 at 40% mc, while the brown variety decreased from 42.72 at 20% mc to 30.77 at 40% moisture content. The yellow variety had bigger size tubers than the brown variety and this has serious implications in packing, handling and transportation issues.

The effect of some extrusion factors on soybean crud residue-based floating fish feed was investigated. Extrusion was conducted at 20%, 25%, and 30% moisture content level, die size of 2 mm, 4 mm and 6 mm, and screw speed of 150 rpm, 200 rpm, and 250 rpm. Pearson square method of fish feed formulation was used to attain a 35% protein content of catfish feed protein requirement. Optimized value of extrusion factors moisture content, die size, and screw speed were 30%, 6 mm, and 150 rpm respectively and the optimized result of responses, expansion rate (ER) floatation rate (FR) sinking velocity (SV) specific mechanical energy (SME) swelling capacity (SC) water absorption index (WAI) water solubility index (WSI) hydration capacity (HC) and hydration index (HI) are 32.73%, 95.87%, 0.024 m s-1, 16.97 kJ kg-1, 1.73, 1.61, 2.76, 0.51, and 0.67 respectively. Feed moisture content and die size have the most significant effect on the physical and functional properties of the extrudate. Coefficient of determination R2 ranges from 0.65 to 0.96, lack of fit not-significant, desirability in optimization of 0.806, suggesting adequacy of research. Soybean crud residue base floating fish feed has been formed and evaluated with an outcome of high efficacy. This extruded producing model can be used for both domestic and industrial scales of catfish feed production.