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Afzelia Africana seeds were subjected to quasi-static parallel plate compression test, using Monsanto Tensometer. The loading orientations were horizontal, vertical and edge-to-edge loading positions at four different moisture content levels of 10.6%, 12.8%, 15.2% and 18.4% wet basis (wb). Slight variations were observed in the means of the physical characteristics at varying moisture content in the range of 10.6% to 18.4%. Loading position was shown to have significant effect on all the mechanical properties studied. The rupture force increased with increase in moisture content in horizontal and vertical loading but did not show consistent trend in variation when loaded on the edges. This value was 155.68N for vertical loading, 139.27 N for horizontal loading and 81.0 N for edge-to-edge loading. Hardness ranged from 6.97 to 6.92 N/mm for horizontal loading, 6.92 to 6.67N/mm for edge-loading and 6.99 to 6.93N/mm for vertical loading respectively in the moisture content range of 10.6 to 18.4% for all cases. Rupture energy varied from 104 to 416.33 N-mm on horizontal loading, 59.96to 241.82 on edge-loading and 190.125 to 419.171 Nmm on vertical loading respectively for the same range of moisture content. Toughness varied from 43.758 to 8.865 N-m/mm, 23.563 to 5.370 and 44.667 to 16.349 N-m/mm for horizontal loading, edge-edge orientation, and vertical loading respectively, for moisture content range of 10.6 to 18.4%.Modulusof Elasticity dropped from 35.657 to 28.133 N/mm2 for horizontal loading, from 51.443 to 14.59 for edge-to-edge loading and 38.087 to 41.04 N/mm2for vertical loading in the range of moisture content of 10.6 to 18.4% respectively. The data generated in this study can be applied when estimating the energy and force needed for shelling the seeds and in making useful suggestions on the loading condition that will demand the least energy for the operation and shelling. The physical properties are also useful in process design and analysis.  http://dx.doi.org/10.4314/njt.v36i3.42

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Investigation of microwave drying of sweet potato slices was conducted at microwave oven power settings of 90, 100, 120 Watts and slice thicknesses of 3mm, 4mm and 6mm using Fourier models and response surface methods. The slice samples dried from initial moisture content of 70.71𝒈𝒘𝒂𝒕𝒆𝒓/𝒈𝒅𝒓𝒚 𝒎𝒂𝒕𝒕𝒆𝒓 to 12.7𝒈𝒘𝒂𝒕𝒆𝒓/𝒈𝒅𝒓𝒚 𝒎𝒂𝒕𝒕𝒆𝒓 final (equilibrium) moisture content in the microwave oven. Fourier models adequately fitted the drying data with the following values of the fit parameters: MBE= 0.00002943 to 0.000645, R² = 0.9987 to 1, RMSE = 0.00384 to 0.01692. Effective moisture diffusion coefficient (𝑫𝒆) of the samples ranged from 𝟏.𝟎𝟖𝟐𝟐 × 𝟏𝟎−𝟑m2/s to 𝟖.𝟑𝟖𝟏𝟐 × 𝟏𝟎−𝟑 m2/s. Analysis of Variance (ANOVA) was used to analyze the effect of drying conditions on the samples parameters at 95% ( p<0.05). The results showed that slice thickness and microwave power have significant effects on the ash and fiber contents of the dried potato samples. At the microwave power of 90 W and slice thickness of 4 mm the values of Fiber and Ash retained in the dried sweet potato samples were optimal at 4.30% and 2.50% respectively, after drying for 390 minutes to an average moisture content of 14.2 gH2O/gdm. Optimized equations for predicting the percent ash and fiber contents at combined factors of microwave power and slice thickness were developed using Response Surface Methodology (RSM) at 95% confidence bound. The coefficients of determination (R2) for the models are 0.7333 and 0.9655 for fiber and ash respectively. These are indications that the models can be used to predict the two food components of microwave dried potato slices. Keywords: RSM, Fourier Model, Microwave, Sweet Potato, Ash, Fiber

Bioethanol production from cellulosic materials is important in mitigating the concomitant displacement and exploitation of primary food crops for biofuel production and reducing carbon emissions which exacerbate climate change. The problem of reduced yield in the production and availability of yeast locally poses a barrier to market adoption and penetration of bioethanol. The study examined the effect of particle size and different yeast strains on the yield of bioethanol from waste sawdust that was sourced from a local timber processing centre. The samples of yeast were prepared from baker’s yeast (Saccharomyces cerevisiae) and palm wine yeast (Saccharomyces chevalieri). The sawdust was reduced to 212 μm, 300 μm, and 500 μm particle sizes. The samples of each particle size were pretreated and hydrolyzed with H2SO4 and fermented with S. cerevisiae or S. chevalieri yeast. The results obtained show that the weight, pH, density, viscosity, flash point, and heating value of the produced bioethanol ranged between 221.67 and 322.64 g, 6.2 and 6.6, 0.821 and 0.878 g/mL, 1.073 and 1.193, 14 and 16°C, and 20.5 and 23.1 MJ/kg, respectively, while the alcohol content of each of the samples was 69%. Furthermore, the bioethanol yield from Saccharomyces cerevisiae yeast was 213.9 mL, 193.2 mL, and 186.3 mL, for the 212 μm, 300 μm, and 500 μm particles, while for Saccharomyces chevalieri yeast, the yield was 289.8 mL, 255.3 mL, and 220.8 mL for the 212 μm, 300 μm, and 500 μm, respectively. An ANOVA on the effect of particle size on ethanol yield shows a significant difference at 5% level of significance. The study demonstrated that the use of locally produced yeast and increasing the surface area of sawdust increase bioethanol yield. Hence, it was concluded that better yeast strain use and biomass particle size reduction to a level that allows the optimal surface area for the reaction improve the yield of bioethanol. The study outcome can help in ameliorating the continued dependence on fossil fuels and the food security problems arising from displacing or utilizing food for fuel and could also encourage commercial-scale cellulosic ethanol production from waste.