J.C. Igbeka

Some physical properties of groundnut kernels

Some of the physical properties of groundnut kernels (Arachis hypogea, also known as peanut or earthnut) were determined and their use for the design of storage, handling, and processing equipment is discussed briefly. At a moisture content of 4.6% d.b., the average length, width and thickness of groundnut kernels were 8.54, 3.55 and 6.93 mm respectively. The geometric mean diameter, sphericity and density were 8.37 mm, 0.76 and 1.01 g/cm3 respectively while the static coefficient of friction varied from 0.47 on galvanized steel to 0.57 on plywood with grain perpendicular to direction of motion. The angle of repose for emptying was 17°.

Osmotic Dehydration of Tropical Fruits and Vegetables

Because of the microstructural complexity of plant tissue, osmotic dehydration cannot simply be explained as a pure osmotic process in which cell membranes act as a semipermeable barrier allowing water to pass through. Instead, osmotic dehydration is considered a process in which many simultaneous mechanisms, acting at different levels, are responsible for mass transport. Different compositional and structural profiles are induced in fruits and vegetables, depending on process variables and the tissue microstructure. Compositional-structural profiles that are developed with gas-liquid exchanges in the tissue during osmotic process have a significant impact on physical (optical), textural and chemical properties (e.g., flavour profile) of the final product, which is in part influenced by the differences in the number of cells that are altered and unaltered during the treatment. This review focuses on changes in the physical, chemical, and cellular structure of fruits and vegetables, some technologies commonly applied to increase mass transfer during osmotic dehydration (OD), potentials and industrial applications of OD, and the challenges of osmo-drying technology.

Some Physical Properties of Two African Yam Bean (Sphenostylis stenocarpa) Accessions and their Interrelations with Moisture Content

The study was undertaken with the objective of determining the size and shape, density, porosity, weight, and volume of two African yam bean accessions (TSs 137 and TSs 138) at four moisture content levels of 4, 8, 12, and 16% wet basis which are useful in the design of harvesting, processing, handling, and storage equipment. The axial dimensions, equivalent diameter, individual grain weight, and volume were found to increase as moisture content increased between 4 and 16% w.b. for the two accessions. With increase in moisture content there was a decrease from 42.67 to 40.96% for porosity, 0.76 to 0.741g/cm3 for bulk density, and 1.326 to 1.255 g/cm3 for true density for TSs 137 while for TSs 138, the decrease was from 45.05 to 43.84%, 0.731 to 0.711 g/cm3, and 1.33 to 1.266 g/cm3, respectively. Sphericity increased between 4 and 8% MC and then decreased between 8 to 16% MC for the two accessions. The effect of moisture content was highly significant on these properties (p < 0.05) and the accessions found not to be statistically different only in terms of sphericity. The frequency distributions for size and shape measurement parameters generally approximated those of the normal distribution. The shape of African yam bean can be described as prolate sphere.

Flow properties of African yam bean (Sphenostylis stenocarpa) as affected by accession and moisture content

Flow properties such as normal stress, shear stress, and initial shear stress, and hopper flow characteristics of two yam bean accessions (TSs 137 and TSs 138) were studied at four moisture content levels (4%, 8%, 12%, and 16 % wet basis) to provide data for the design of handling and storage equipment. Two experimental designs were used: Randomized complete block design (RCBD) with one observation per cell, and split plot in RCBD. The initial shear stress increased with moisture content from 1.31 to 2.91 g/cm2 for TSs 137, while it increased from 1.58 to 3.09 g/cm2 for TSs 138. The hopper side wall slope for the two accessions increased with moisture content from 60.21³ to 64.06³. The hopper opening size required increased with moisture content and more than doubled at the highest value of moisture content studied, while the coefficient of mobility decreased with moisture content from 0.33 to 0.24. The accessions were found not to be statistically different in terms of shear stress, coefficient of mobility, and side wall slope, but were statistically different in terms of normal stress, initial shear stress, and hopper opening dimensions. The methods of calculation of coefficient of mobility were observed not to be statistically different, and the effect of normal loads and type of hopper opening was highly significant. There was also a highly significant effect of moisture content on all the flow properties (p < 0.05).

Mathematical Modelling of Thin Layer Dried Cashew Kernels

ABSTRACT In this paper mathematical models describing thin layer drying of cashew kernels in a batch dryer were presented. The range of drying air temperature was 70 – 110°C. The initial moisture content of the cashew kernels was 9.29% (d.b.) and the final moisture content was in the range of 3.5 to 4.6% dry-basis. Seven different thin layer mathematical drying models were compared according to their coefficients of determination (R2) mean square error (MSE) and mean relative deviation modulus (P) to estimate drying curves. The effects of the drying air temperature and time on the drying model constants and coefficients were predicted by multiple regression analysis using linear and non-linear type models. The results have shown that among the models, the Page model was found to be the best for describing the drying behaviour of cashew kernels with R2, MSE and P values of 0.9830, 0.00311 and 5.046 respectively.

EFFECT OF MOISTURE CONTENT AND POWER INPUT ON THERMAL CONDUCTIVITY OF AFRICAN YAM BEAN (SPHENOSTYLIS STENOCARPA)

Thermal conductivity of two African yam bean accessions (TSs 137 and TSs 138) was determined at four moisture content levels (4%, 8%, 12%, and 16% wet basis) and four power input (rate of heating) levels (0.900, 2.025, 3.600, and 5.625 watts) to provide information for processing, storage, and utilization. The experimental design used was split plot in randomized complete block design (RCBD). The line heat source method was used for measurement of thermal conductivity. Thermal conductivity increased with increase in moisture content for the two accessions at all power input (rate of heating) levels. For all accessions, moisture contents, and power input levels, thermal conductivity values ranged from 0.2097 to 0.3065 w/m ³C. There was a highly significant statistical difference (p < 0.05) in the thermal conductivity values of the two accessions. The effect of moisture content and power input on thermal conductivity was highly significant (p < 0.05), indicating that time and temperature of exposure to heat is critical in processing and storage of African yam bean.

Selected Moisture Dependent Friction Properties of Two African Yam Bean (Sphenostylis stenocarpa) Accessions

Friction properties such as angle of repose, coefficient and angle of internal friction, and coefficient of friction on material surfaces of two African yam bean accessions (TSs 137 and TSs 138) at moisture content levels of 4, 8, 12 and 16% wet basis (w.b.) were determined for use in the design of planting, processing, handling, and storage equipment. For this study, 2 U 4 factorial in Complete Randomized Design (CRD) and Split Plot in Randomized Complete Block Design (RCBD) were employed. The angle of repose was measured using the cylinder method. The coefficient of friction was measured by the force required to slide a cell filled with African yam bean on the material surface. Coefficient and angle of internal friction were determined by providing a grain bed instead of material surface. The angle of repose and coefficient and angle of internal friction showed an increase with an increase in moisture content. The angle of repose increased from 17.47 to 26.07. for TSs 137 and 15.71 to 35.38. for TSs 138. The coefficient and angle of internal friction for the two accessions ranged from 0.59 to 0.78 and 30.41 to 38.11., respectively. The coefficient of friction on material surfaces ranged from 0.30 to 0.60 for all accessions, material surfaces, and moisture contents. The effect of material surface on coefficient of friction and moisture content on all friction properties was highly significant (p < 0.05). The two accessions were statistically different (p < 0.05) with respect to angle of repose and not statistically different with respect to coefficient of friction on material surfaces and coefficient and angle of internal friction.

Predicting Selected Quality Attributes in Parboiled Rice

Models were developed to predict the quality of parboiled rice. The quality attributes investigated were translucency, broken grain, deformed grain, and color. The parboiling parameters used were soaking temperature, equilibration time, soaking time, moisture content after soaking, steaming time, moisture content after steaming, drying temperature, moisture content after drying, and tempering treatments.

Modeling for Drying of Thin Layer of Native Cassava Starch in Tray Dryer

Ndubisi A. Aviara*, Joseph C. Igbeka Department of Agricultural and Environmental Resources Engineering, University of Maiduguri, Maiduguri, Nigeria Department of Agricultural and Environmental Engineering, University of Ibadan, Ibadan, Nigeria Received: June 27th, 2016; Revised: August 31st, 2016; Accepted: October 12nd, 2016 Purpose: The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of 40-60°C. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between 40-55°C. Drying at 60°C occurred only in the falling rate phase. The critical moisture content was observed in the 40-55°C range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to 60°C. The modified Hii et al. model produced randomized residual plots, the highest R2, and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between 40-55°C. The constant drying rate phase occurred without any period of induction over a temperature range of 40-55°C prior to the falling rate period, while drying at 60°C took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

Performance evaluation of a roaster for groundnut and palm kernel nut

No Abstract. Journal of Applied Science, Engineering and Technology Vol. 1(1) 2001: 67-70