Browsing by Author "Raji, A. O."

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Design and Construction of a Lyophilizer system using locally available material
(Nigerian Society of Engineers, 2017) Bello, R. O.; Raji, A. O.; Oyefeso, B. O.
A lyophilizer system was designed and constructed with a galvanized metal sheet to reduce the cost and to make it available to local and poor food processors. It consists of 330.2 mm x 508 mm x 457.2 mm rectangular shaped chamber with the inner and outer layer reinforced with a hollow mild steel square pipe of 17 x 1.7 mm to prevent implosion of the lyophilizer during dehydration phase. The system was designed based on the specific heat capacity of Pears, Tomatoes and Carrot with values of 3.62 kJ/kg C, 3.98 kJ/kg C and 3.79 k/kg C respectively. The results showed that dry-bulb temperature of 28°C at initial stage and 1°C after drying while the dew point temperature of 20.8°C at initial stage and -6.1°C after drying were recorded. The result obtained also shows that the temperatures (dry-bulb and dew point) and relative humidity of the lyophilized product is lower as compared to the imported ones. A total of 6hours was used for freeze drying with 1/10 reduction in weight of the lyophililized product when weighed.
Effect of moisture content and loading orientation on elasticity of cocoyam cormel during transit and storage
(International Commission of Agricultural and Biosystems Engineering (CIGR), 2017) Raji, A. O.; Oyefeso, B. O.
Cocoyam (Xanthosoma sagittifolium) is one of the major staple food items in Nigeria. The crop is recently gaining attention and there is urgent need to intensify research efforts towards fully exploiting its promising potentials. Information on the elastic properties of the cocoyam cormels are necessary for understanding their behaviour under loading and in the design of equipment for proper handling of the cormels during processing and storage. This study investigated the effects of moisture content and orientation of loading on the elasticity of cocoyam cormels. White-fleshed and pink-fleshed varieties of the X. sagittifolium cormels were used for this study. The elastic properties of the cormels along the three mutually-perpendicular axes were determined. Deformation at rupture, modulus of elasticity (MOE), degree of elasticity (DOE) after first and third cycles along the longitudinal, cross-sectional and transversal directions ranged from 5.14 and 11.64 mm, 3.03 and 11.70 N mm-2, 0.51 and 0.73 mm, 0.45 and 0.70 mm, respectively. The degrees of elasticity of the cormels decreased with the increasing number of loading and unloading cycles thereby, limiting the stack height of cocoyam cormels in transit and storage to reduce mechanical damage and subsequent postharvest losses. The study provides the information which can serve as guidelines in ensuring proper handling of cocoyam cormels in transit and storage.
Effect of moisture content and loading orientation on selected mechanical properties of cocoyam cormel
(Nigerian Institution of Agricultural Engineers (NIAE), 2020) Oyefeso, B. O.; Raji, A. O.
Cocoyam, Xanthosoma sagittifolium, is a major staple food in many African countries including Nigeria. The crop has been under-utilized and there is need for more research input to fully exploit it. There is dearth of information especially in terms of the mechanical properties among other important engineering properties which are significant in designing equipment for handling and processing the cormels. This study therefore, investigated the effect of moisture content and orientation of loading on some mechanical properties of the cocoyam cormels. White- and pink-fleshed varieties of the X. Sagittifolium cormels were used for this study. Selected mechanical properties namely rupture force, compressive strength, stiffness and toughness of the cormels along the three mutually-perpendicular axes were determined at four moisture content levels using Universal Testing Machine (UTM). The rupture force, compressive strength, stiffness and toughness of the cocoyam cormels along the longitudinal, cross-sectional and transverse directions ranged between 361.40 and 1,093.60N, 0.53 and 2.51 Nmm-2, 3.03 and 11.70 Nmm-2 and 0.62 and 5.37 Nm respectively. The study further confirmed the moisture-dependence and anisotropic nature of cocoyam cormel as a biological material.
Effect of thickness and pre-treatment on drying kinetics of cocoyam
(International Commission of Agricultural and Biosystems Engineering (CIGR), 2020) Oyefeso, B. O.; Raji, A. O.
Cocoyam (Xanthosoma sagittifolium) corms and cormels are among the staple foods in Nigeria. The cormels are processed into cocoyam flour and utilized for various purposes. Drying is an essential unit operation in the conversion of the cormels into cocoyam flour and the knowledge of the effect of drying variables on the drying characteristics of the cormels is necessary for analysis, optimization and control of the drying process. This study therefore, investigated the drying kinetics of cocoyam cormels as influenced by slice thickness and pre-drying treatment. White-fleshed (NXs. 001) and pink-fleshed (NXs. 002) cocoyam cormels were used for this study. Drying kinetics of the pre-treated cormels (blanched by soaking in hot water at 100oC for 5 minutes) and fresh cormel slices of 2, 3 and 4 mm thicknesses were examined at 60oC. Drying of the cocoyam slices was predominantly in the falling rate period which indicated that moisture removal occurred mainly by diffusion. Drying of thin pre-treated slices of cocoyam cormels is recommended to obtain the faster moisture removal and subsequently, a reduction in the drying period.
Effect of thickness and pre-treatment on drying kinetics of cocoyam
(International Commission of Agricultural and Biosystems Engineering (CIGR), 2020) Oyefeso, B. O.; Raji, A. O.
Cocoyam (Xanthosoma sagittifolium) corms and cormels are among the staple foods in Nigeria. The cormels are processed into cocoyam flour and utilized for various purposes. Drying is an essential unit operation in the conversion of the cormels into cocoyam flour and the knowledge of the effect of drying variables on the drying characteristics of the cormels is necessary for analysis, optimization and control of the drying process. This study therefore, investigated the drying kinetics of cocoyam cormels as influenced by slice thickness and pre-drying treatment. White-fleshed (NXs. 001) and pink-fleshed (NXs. 002) cocoyam cormels were used for this study. Drying kinetics of the pre-treated cormels (blanched by soaking in hot water at 100oC for 5 minutes) and fresh cormel slices of 2, 3 and 4 mm thicknesses were examined at 60oC. Drying of the cocoyam slices was predominantly in the falling rate period which indicated that moisture removal occurred mainly by diffusion. Drying of thin pre-treated slices of cocoyam cormels is recommended to obtain the faster moisture removal and subsequently, a reduction in the drying period.
Effects of particle size, stem component and genotype on absorbency of kenaf (hibiscus cannabinus L.) grown in Nigeria for oil spill clean-up
(Scientific Research Publishing Inc., 2016) Balogun, M. O.; Raji, A. O.
The efficacies of different products made from different parts of the stem of different varieties of kenaf grown in Nigeria as oil absorbents were tested. Particle sizes, genotypes and whether mixed or sole stem core or bast differed among the treatments. The fibre component sank in water, and so was not buoyant; the core was partially buoyant while the mixed fibre and core was completely buoyant. Sorption capacity was the highest in the ground whole stem (8.16 g oil/g sorbent), which also retained (6.31 g oil/g sorbent) the highest quantity of oil. Sorption and retention of oil were the lowest in the fibre (1.66 and 0.69 g oil/g sorbent, respectively). After the first use, only the ground stem can be used to re-absorb up to 1.97 g oil/g sorbent of used sorbent. A mixture of genotypes was more absorbent than a single genotype. The implications of these findings in absorbency research are discussed.
Estimating Mass and Volume of Nigerian Grown Sweet and Irish Potato Tubers using their Geometrical Attributes
(Adeleke University, 2018) Oyefeso, B. O.; Raji, A. O.
Sweet and Irish potato are tuber crops which have been domesticated and cultivated in different parts of the world including Nigeria. They are often prepared in various ways for food. A good knowledge of the physical properties of these tuber crops will enhance proper design of post-harvest processing machines and handling equipment with high level of performance. Also, functional relationships established between the various physical properties of these crops could assist in ensuring proper handling and more efficient and economical processing. This study was therefore, aimed at developing mathematical models for predicting the mass and volume of sweet and Irish potato tubers using some of their geometrical attributes. The research was conducted on fresh sweet and Irish potato tubers which were sorted into four fractions based on their individual mass. The physical characteristics measured include the mass, volume, linear dimensions (length, width and thickness) and the projected areas taken along the three mutually-perpendicular axes. The models were divided into three classifications namely: single and multiple variable regression models based on linear dimensions; single and multiple variable regression models based on the projected areas; single variable regression models based on mass or volume. Mass and volume models based on the projected areas and the volume were the best models for both crops. The highest coefficient of determination (R2) for sweet potato was obtained for mass model based on the projected area along the longitudinal plane (R2 = 0.981) while mass model expressed on the basis of the multiple regression of the three linear dimensions performed best (R2 = 0.968) for Irish potato. This study provided useful information that can help in the design of systems for handling and processing of sweet and Irish potato tubers.
Evaluation of three methods for estimating leaf area index of cowpea (Vigna unguiculata)
(Kuwait University, Faculty of Engineering and Petroleum, 2011-03) Ewemoje, T. A.; Raji, A. O.
Leaf Area Index (LAI) is a concept that cuts across agricultural sciences and agricultural engineering with an encapsulating feature in environmental engineering. It is one of the most difficult to quantify properly owing to large spatial and temporal variability. This paper discusses briefly LAI and the use of three methods which are non-destructive in determination of its value for cowpea, namely: the empirical formulae, the graphical and the image processing methods. Cowpea seeds were planted and samples were marked for determination of LAI by the three methods. The results showed that image processing as a more accurate and promising method compared to the other two
Features extraction in agricultural products using computer image processing
(Nigerian Society of Engineers, 2016) Raji, A. O.; Oyefeso, B. O.
The study was based on the application of image processing and machine vision technology in the extraction of some features of interest in agricultural products. It involved the development of an algorithm that used some computer programs written in the FORmular TRANslation (FORTRAN 95) programming language to carry out tests on some input data images. The input data images were obtained by digitizing the original images of some Amaranthus vegetables, cowpea seedlings and some food samples on which some fungi were found to be growing as captured by a digital camera. The results of this study carried out on the images showed that the algorithm was able to extract both the boundary of the leaves and the crop position by discriminating between the crop and the uncovered soil surface as well as the growth of the fungi on the food samples. The extracted images as produced by the programs compared favourably well with the original images as captured by the digital camera. This visual comparison showed that the approach is very promising in developing automated sorting and quality inspection techniques which can be applied to some agricultural and food products.
Hydrological responses to climate and land use changes: the paradox of regional and local climate effect in the Pra River Basin of Ghana
(Elsevier Ltd., 2020) Bessah, E.; Raji, A. O.; Taiwo, O. J.; Agodzo, S. K.; Ololade, O. O.; Strapasson, A.
Study Region: Pra River Basin, Ghana. Study Focus: The study modelled the changes in water yield using regional, sub-regional and local climate conditions from modelling outputs at spatial resolutions of 44 km, 12 km and 0.002 km respectively to drive the Integrated Valuation of Ecosystem Services and Trade-offs model at three time periods of land use land cover (LULC). Changes in historical water yield (simulated for 1986, 2002 & 2018 LULC using the mean climatic parameters from 1981-2010) and future scenario (simulated for 2018 LULC using the mean climatic parameters from 2020-2049) for annual, seasonal and monthly periods were assessed. New Hydrological Insights for the Region: The results show that future annual water yield could change by -46%, -48%, +44% and -35% under the regional, sub-regional, local and ensemble mean of the climate scenarios respectively. Seasonal water yield from the ensemble mean of the future climate scenario was projected to decrease between 2-16 mm, with a mean decrease of 33.39% during the December–February season. There was no directional effect of spatial resolution on water yield. The future period could be impacted by both drought and flood. We recommend that re/afforestation should be encouraged to improve infiltration and reduce deforestation which was 2.27% per annum in the assessed period to prevent flood causing runoffs, while irrigation technology will help to improve resilience to drought.
The impact of varying spatial resolution of climate models on future rainfall simulations in the Pra River Basin (Ghana)
(IWA Publishing, 2020) Bessah, E.; Raji, A. O.; Taiwo, O. J.; Agodzo, S. K.; Ololade, O. O.
This work compares future projections of rainfall over the Pra River Basin (Ghana) using data from five climate models for the period 2020–2049, as referenced to the control period 1981–2010. Bias-correction methods were applied where necessary and models’ performances were evaluated with Nash–Sutcliffe Efficiency, root-mean-square error and coefficient of determination. Standardised Anomaly Index (SAI) was used to determine variability. The onset and cessation dates and length of the rainy season were determined by modifying the Walter–Olaniran method. The ensemble means of the models projected a 1.77% decrease in rainfall. The SAI showed that there would be drier than normal years with the likelihood of drought occurrence in 2021, 2023, 2031 and 2036. The findings showed that high-resolution models ( 25 km) were more capable of simulating rainfall at the basin scale than mid-resolution models (26–150 km) and projected a 20.13% increase. Therefore, the rainfall amount is expected to increase in the future. However, the projected increase in the length of the dry season by the ensemble of the models suggested that alternative sources of water would be necessary to supplement rainfed crop production for food security.
Moisture-dependent thermal properties of Cocoyam cormels
(Faculty of Engineering, University of Maiduguri, Nigeria, 2019) Oyefeso, B. O.; Raji, A. O.
"Cocoyam (Xanthosoma sagittifolium) has served as a cheap carbohydrate source for many people in the developing countries with prospects in the production of animal feed, lager beer, and its starch as binding agent in drug formulation. Drying is an important unit operation in cocoyam processing and there appears to be lack of information on the thermal properties which are significant in designing heat treatment systems such as dryers for the cormels. This study therefore, investigated some thermal properties of X. sagittifolium cormels as affected by moisture content. Thermal properties namely thermal conductivity, diffusivity and specific heat of white- and pink-fleshed cocoyam cormels were investigated at moisture contents within the ranges of 130 to 395% and 85 to 200% (dry basis), respectively. The selected thermal properties of the cormels were determined with the aid of a thermal properties analyser which has a dual needle probe and uses transient line heat source method. Thermal conductivity, diffusivity and specific heat were within the ranges of 0.454 to 0.562 Wm-1K-1, 1.62×10-7 to 2.32×10-7 m2s-1, 1.836to 4.029 kJkg-1K-1, respectively for white-fleshed cocoyam and 0.489 to 0.601 Wm-1K-1, 1.79×10-7 to 2.65×10-7 m2s-1, 1.615 to 2.991 kJkg-1K-1, respectively for pink-fleshed cormels. Analysis of variance showed that there were significant differences between the measured properties at different moisture content levels. Regression models were established between the investigated thermal properties and moisture content.
Physical characterisation and development of mass and volume models for tannia (Xanthosoma sagittifolium) cormels
(International Commission of Agricultural and Biosystems Engineering (CIGR), 2024) Oyefeso, B. O.; Raji, A. O.
Physical properties of agricultural products are important for proper mechanization of their processing and handling operations. Models established based on these physical properties can also take a role in the automation systems and ensure efficient processing. This study determined some physical characteristics of tannia cormel and developed mathematical models for estimating its mass and volume using its geometrical attributes. Linear dimensions were within the range of 20.87-168.30 mm while the projected areas were within the range of 4.63-207.72 cm2. Average mass, volume and density were within the ranges of 7.40-256.80 g, 7.00-215.00 cm3 and 947.37-1565.45 kg m-3, respectively. Average sphericity, aspect ratio, shape index, eccentricity and elongation ratio were 0.73, 0.60, 1.84, 0.76 and 1.81, respectively. The results showed that tannia cormels are closer to being prolate spheroid in shape with relatively high sphericity. The mass and volume of tacca cormel can be reliably predicted using its projected areas and volume (for mass modelling only). The most suitable of all the models was obtained for mass model with respect to volume (R2 = 0.976). Data provided in this study are useful in the development of postharvest handling and processing systems for tannia cormels.
Prediction of mass and volume of Tacca Involucrata tubers using physical characteristics
(Faculty of Engineering, University of Maiduguri, Nigeria, 2021) Raji, A. O.; Oyefeso, B. O.
Knowledge of physical properties of crops is necessary for the development of processing machines. Relationships between the various physical properties of crops could also be useful in ensuring proper handling and more efficient design of processing machineries. This study was therefore, aimed at developing mathematical models for predicting the mass and volume of Tacca involucrata tubers using some physical characteristics of the crop. Physical characteristics of Tacca tubers at average moisture content of 73.3% (wet basis) namely axial dimensions, Arithmetic Mean Diameter (AMD), Geometric Mean Diameter (GMD), projected areas along the three mutuallyperpendicular axes, criterion area (Ac), mass and volume were determined. Out of 240 samples used in the study, data from 120 samples were used for development of the prediction models while the remaining were used for validation of the developed models. Data analysis tool in Microsoft Excel (2013 version) was used to carry out regression analysis and develop the predictive models. Statistical parameters namely correlation coefficient, coefficient of determination, root mean square error and mean bias error were used to determine the goodness of fit of the predictive models. The mass and volume models were divided into three classifications namely: single and multiple variable regression models based on axial dimensions; single and multiple variable regression models based on the projected areas; single variable regression model based on volume (for mass prediction only). Average length, width, thickness, AMD and GMD of the tubers were 71.88, 57.22, 46.71, 58.60 and 57.57 mm respectively while average criterion area, longitudinal, cross-sectional and transversal projected areas were 2614.24, 2580.61, 2097.04 and 3165.07 mm2 respectively. Average mass and volume of the tubers were 129.30 g and 111.55 cm3 respectively. All the developed models performed well in predicting the mass and volume of Tacca tubers (R2 ≥ 0. 905) except for those based on the axial dimensions as single independent variables (R2 ≤ 0.890). The predicted mass and volume of Tacca tubers were not significantly different (p ≤ 0.05) from the experimentally observed values for all the classifications considered. Mass and volume modelling based on a single variable of any of the projected areas was the most convenient modelling for Tacca tubers since it involves the use of a single image capturing device and the whole measurement could therefore, be automated. The developed models would be useful for automated sorting and packaging of Tacca tubers.
Suitable model for thin layer drying kinetics of white and pink-fleshed tannia (Xanthosoma Sagittifolium) cormels
(LAUTECH, 2020) Oyefeso, B. O.; Raji, A. O.
Drying is an essential unit operation in the conversion of fresh tannia (Xanthosoma sagittifolium) cormels into flour with the attendant benefits of improved shelf life and better storability. Information on the drying kinetics of the cormels will foster a good understanding of its behaviour during drying. Rate of moisture loss during the process can also be described by appropriate models. This study therefore, investigated the thin layer drying kinetics of two cultivars of tannia cormels at different temperature levels and determined the most suitable model for its prediction. White and pink-fleshed cormel slices of 3mm thickness were dried at 60, 70 and 80oC temperature levels. Data obtained from the drying experiments were fitted into ten selected models namely Newton, Page, modified Page, Logarithmic, Henderson and Pabis, Midilli, Verma, Two term, Thompson, and Wang and Singh models. The highest and the lowest drying rates were obtained at 80 and 60oC respectively. Page and modified Page models were the most suitable models for describing the drying behaviour of both tannia cultivars with highest R2 in excess of 0.9941 and lowest error estimates (RMSE ≤ 0.0251; X2 ≤ 0.0008; MBE ≤ 0. 0060). The drying took place predominantly in the falling rate period which indicated that moisture removal from tannia cormels occurred mainly by diffusion mechanism.
Variable resolution modeling of near future mean temperature changes in the dry sub-humid region of Ghana
(Springer, 2018-05) Bessah, E.; Raji, A. O.; Taiwo, O. J.; Agodzo, S. K.; Ololade, O. O.
The study used two models from Rossby Centre Regional Atmospheric Model (RCA4) and two from Weather Research and Forecasting Model (WRF) plus the Statistical Downscaling Model—Decision Centric (SDSM-DC) at 44 km, 12 km and 2 m resolution respectively to project the impact of climate change on mean temperature in the Pra River Basin for the period 2020–2049. Results showed that the minimum temperature increased (+ 1.47 °C) faster than the increase (+ 1.11 °C) in maximum temperature for observed period 1981–2010. An evaluation of the performance of the models with time-series based metrics showed that SDSM-DC and RCA4 are better for projecting mean temperature in the study area compared to WRF despite its resolution. Analysis of variance (p < 0.05) indicated significant difference between the projected mean temperature of the five models but there was no significant difference between SDSM-DC and RCA4 models. Correlation between models was highest at R = 0.727 between SDSM-DC and RCA4. The years 2041, 2042 and 2047 were projected as hottest by minimum two different models. The mean temperature change was projected at + 1.36, + 1.42 and + 1.12 °C by SDSM-DC, RCA4 and WRF respectively. The ensemble of projection depicted same trend of February—April as the high mean temperature and July—September as the lowest as was for the observed period. However, January is projected to have the highest change in mean temperature of + 1.51 °C. The maximum temperature for observed period was found to be the mean temperature in the period 2020–2049. Future study will focus on the impact of projected temperature change on ecosystem services delivery in the region.