ResumoAs características da adsorção de umidade de amostras de gengibre secas foram estudadas para se determinar o efeito das condições de armazenamento com o propósito de se prever a vida de prateleira ou validade, a seleção de materiais apropriados para empacotamento, avaliar a bondade de ajuste dos modelos de sorção e determinar a termodinâmica da adsorção de umidade para aplicação em secagem. Houve um efeito significativo (p ≤ 0,05) da atividade de água, da temperatura e do pré-tratamento sobre o teor de umidade de equilíbrio higroscópico das amostras de gengibre secas. Sob atividade de água constante (a w ), o teor de umidade de equilíbrio higroscópico (CEM) diminuiu com o aumento da temperatura. O teor de umidade de equilíbrio higroscópico de todas as amostras aumentou com o aumento da atividade de água, sob temperatura constante. A umidade de sorção das amostras de gengibre com casca foi maior do que a das amostras de gengibre sem casca enquanto que a das amostras de gengibre não escaldo com e sem casca foi maior do que a das amostras de gengibre escaldado com e sem casca. A equação de Henderson permite previsões mais exatas das isotermas com o menor valor de média quadrática percentual (%RMS) e, portanto, descreve melhor os dados de adsorção dos modelos de Guggenheim Anderson De-Boer (GAB), Oswin e Halsey, nesta ordem. A umidade de monocamada, em geral, diminuiu com a temperatura em todas as amostras. O calor isostérico diminuiu quando o teor de umidade se aproximou do valor assimptótico ou o calor latente de vaporização da água pura (∆H st = 0), enquanto que a entropia de sorção aumentou com o teor de umidade. Palavras-chave: modelos de sorção; termodinâmica; atividade de água; amostras de gengibre. AbstractThe moisture adsorption characteristics of dried ginger slices was studied to determine the effect of storage conditions on moisture adsorption for the purpose of shelf life prediction, selection of appropriate packaging materials, evaluate the goodness-of-fit of sorption models, and determine the thermodynamics of moisture adsorption for application in drying. There was a highly significant effect (p ≤ 0.05) of water activity (a w ), temperature, and pre-treatment on the equilibrium moisture content (EMC) of the dried ginger slices. At constant a w , the EMC decreased as temperature increased. The EMC of all samples increased as the a w increased at constant temperature. The sorbed moisture of the unpeeled ginger slices was higher than the peeled while those of unblanched samples were higher than the blanched. Henderson equation allows more accurate predictions about the isotherms with the lowest %RMS, and therefore, it describes best the adsorption data followed by GAB, Oswin, and Halsey models in that order. The monolayer moisture generally decreased with temperature for all samples. The isosteric heat decreased with moisture content approaching the asymptotic value or the latent heat of vaporization of pure water (∆H st = 0) while the entropy of sorption was observed to increase with moisture con...

The choice of agro waste for the production of briquettes for domestic and industrial cottage utilization depends on the residues’ physical and fuel characteristics. This study investigate the physical and fuel characteristics for both the residues and blends of rice hull, groundnut shell and corncob. The residues were subjected to size reduction process and variance analysis was used to establish the influence of each sample blends.  Different samples of briquettes were produced by blending rice hull (R), groundnut shell (G) and corncob(C) with different ratios of R:G:C respectively using cassava starch as a binder. The residue’ dimensions and densifications of the sample briquettes were determined using standard methods.The results revealed the following ranges of values; For the compressed residues, density (0.075 - 0.099Kg/m3), volume (0.001 - 0.002m3), height (1.0357 - 1.0343m). For the relaxed residues, density (0.049 - 0.210Kg/m3), volume (0.0001 -0.0002m3), height (1.0357 - 1.0343m). The residual density of rice hull, groundnut shell and corncob are 104, 105, and 103 (Kg/m3) respectively. The densification; compressed density (461.22 - 627.24 Kg/m3), relaxed density (285.47 - 393.63 Kg/m3), density ratio (0.56 - 0.66), relaxation ratio (1.52 - 1.79), and compaction ratio (1.46 to 2.01). Blend formulations affected the combustion characteristics of the briquettes, with low moisture briquettes possessing higher calorific values. The briquette formulation containing ratio 50:20:30 of rice hull: groundnut shell: corncob respectively had more positive attributes of biomass fuel such as lower relaxation ratio and high compaction ratio than the control and other formulated briquettes in this study. Generally, significant (p<0.05) differences existed between the samples in almost all the parameters.Keywords: Briquettes, Corn comb, Densification, Fuel Characterization, Groundnut shell, Rice hull.

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Gelatinized white yam cubes, having a moisture content of 196% dry basis were dried in a convective dryer under different conditions of air temperature (40, 50, 60 and 70°C) and relative humidity (20 - 50%). There was no constant rate period throughout the entire drying period as drying took place entirely during a falling rate period. The effect of temperature was more pronounced than that of relative humidity. The drying data were fitted to five thin-layer drying models. The goodness of fit of the models were evaluated by comparing the percent mean relative deviation modulus (E%), RMSE, χ2 and R2 between their observed and predicted moisture ratio. The Binomial approximation of Fick's diffusion equation gave the best fit to the drying data as the highest values of R2 and the lowest values of χ2 and RMSE were consistently obtained with the Binomial model equation.

Physical and frictional properties were determined for shelled (i.e. hulled) seeds of egusi melon (Citrullus lanatus Thunb) at moisture content levels of 11.04, 15.7, 21.03 and 24.78 % dry basis. The physical properties investigated were true density, bulk density and the angle of repose; while the frictional properties were the coefficient of static friction and the coefficient of internal friction.  Densities were determined using the volume displacement method, while the bulk porosity was calculated as a function of the true and bulk densities. The angle of repose was measured using the cylinder method. The coefficient of static friction of melon seeds on the surfaces of plywood, galvanized iron and glass was determined by sliding a cell filled with the seeds on a tilting table overlaid with the test material surfaces. The coefficient and internal angle of friction were determined by means of a shear test apparatus. Within the range of moisture investigated, the true density of shelled melon seeds decreased from 1,264 to 1,239 kg/m3 while its bulk density increased from 668 to 681 kg/m3. The porosity decreased from 47.19 to 45.36 % while the angle of repose increased from 31.0 to 34.9°. The coefficient of friction of shelled melon seeds on the surfaces of glass, galvanised iron and plywood  increased from 0.329 to 0.475, 0.364 to 0.476 and 0.408 to 0.559 respectively. The coefficient and angle of internal friction increased from 0.638 to 0.668 and 32.52 to 33.74°, respectively. These findings are valuable data for efficient design of machines for processing, handling and storage of hulled seeds of egusi melon.