A pinboard by
Daniel Onwude

I am a Lecturer and academic researcher. My research focuses on modelling and simulation of food.


Infrared-A modern tool for quality food and agricultural products

The Most Common Method of Food Preservation and Processing:

Drying of agricultural crops is a very important postharvest operation. However, drying is an energy-intensive process and it consumes more than 20% of the total energy of food processing industry in the world. In addition, the conventional drying methods could also significantly reduce the quality of final products. This attribute, together with the requirement of energy efficiency call for the development of novel drying methods for food and agricultural products.

The need for novel drying methods:

A number of novel thermal hybrid drying methods have recently been researched as potential alternatives to conventional drying techniques. Particularly, the combined infrared and hot-air drying method has been identified to be able to improve both energy efficiency and quality of dried agricultural crops. However, being a novel drying technique, studies on its application to the drying of industrial crops such as sweet potato are still limited. Particularly, the drying kinetics, drying conditions, and quality attributes during drying of sweet potato are not properly investigated. The most appropriate combination mode is yet to be known. There is also currently little information available on the shrinkage phenomenon during combined infrared and hot-air drying. The heat and mass transfer mechanism during different combination modes is also still not fully understood.

The Solution:

The potential of combined infrared and hot-air during sweet potato (Ipomoea batatas L.) drying considering the drying kinetics, specific energy consumption (SEC), colour and microstructural changes of sweet potato (Ipomoea batatas L.) has been studied. The combined computer vision (CV) and laser-light backscattering imaging was adopted to monitor the shrinkage and quality attributes. This study also examined the performance of different combined infrared (IR) and hot-air drying (HAD) strategies for sweet potato. Fundamental physics-based theoretical models based on Lambert’s equation of electromagnetics for single-phase and multiphase change during the combined IR and HAD of sweet potato were developed, using finite element methods in both COMSOL and MATLAB software. The results of this study indicated that performance of combined CV and backscattering imaging could be significantly affected by drying temperature and time. The relationship between dimensionless moisture content and shrinkage of sweet potato in terms of volume, surface area, perimeter and illuminated area was found to be linearly correlated. It was also demonstrated that the shrinkage of sweet potato based on CV and backscattered optical parameters varied with the product thickness, drying temperature and drying time. The combined IR and HAD resulted in 69.34 – 85.59% reduction in the SEC of HAD. Dried sweet potato slices using combined IR and HAD at 1100 W/m2 intensity showed the best colour attributes. This novel drying method was found to be more efficient compared to HAD alone and IR drying. The specific energy consumption during simultaneous IR and HAD, two-stage HAD+IR, two-stage IR+HAD, and intermittent IR and HAD varied between 27.47-103.56 kWh/kg, 26.61-49.30 kWh/kg, 17.10-18.99 kWh/kg, 27.67-41.44 kWh/kg, respectively. The effective moisture diffusivity and activation energy with and without shrinkage for all combined IR and HAD varied from 8.366 x 10-9 m2/s to 9.476 x 10-8 m2/s and 8.74 kJ/mol to 36.44 kJ/mol, respectively.


Microwave drying of germinated corn and its effect on phytochemical properties.

Abstract: Drying is a preservation method that removes or reduces the moisture content of a product. This process could affect the nutritional properties of agricultural crops. Therefore, this research seeks to investigate the effect of microwave drying power (100-700 W) on drying rate, effective diffusivity, antioxidant value of beta-carotene content (BCC), total flavonoid content (TFC), total phenolic content (TPC), and the antioxidant capacity of sprouted corn, which can be applied as a rich antioxidant source.With increasing microwave drying power from 100 to 700 W, the effective diffusivity (Deff ) was in the ranges of 1.50 × 10(-6) to 1.81 × 10(-5) m(2) s(-1) , BCC ranged from 614.20 ± 3.10 to 229.90 ± 1.00 µg BCE g(-1) dw and decreased gradually by 62.57 %. Meanwhile, TPC and TFC of samples dried at 300 W were the highest ones with amounts of 315.94 ± 0.69 mg GAE g(-1) dw and 190.16 ± 1.33 mg CAE g(-1) dw, respectively which were higher by 8.66 % and 98.97 % as compared to samples dried at 100 W. Similar development was found in antioxidant ability of germinated corn.Drying at microwave power of 300 W provided the highest nutritive and antioxidant values. The results of this study are useful in the selection of optimum drying conditions during microwave drying of germinated corn, as a baseline for other agricultural crops.

Pub.: 20 Nov '16, Pinned: 22 Apr '18

The Potential of Computer vision, Optical Backscattering Parameters and Artificial Neural Network Modelling in Monitoring the Shrinkage of Sweet Potato (Ipomoea Batatas L.) during Drying.

Abstract: Drying is a method used to preserve agricultural crops. During the drying of products with high moisture content, structural changes in shape, volume, area, density and porosity occur. This changes could affect the final quality of dried product and also the effective design of drying equipment. Therefore, this study investigated a novel approach in monitoring and predicting the shrinkage of sweet potato during drying. Drying experiments were conducted at temperatures of 50-70 °C and samples thicknesses of 2 - 6 mm. The volume and surface area obtained from camera vision, and the perimeter and illuminated area from backscattered optical images were analysed and used to evaluate the shrinkage of sweet potato during drying.The relationship between dimensionless moisture content and shrinkage of sweet potato in terms of volume, surface area, perimeter and illuminated area was found to be linearly correlated. The results also demonstrated that the shrinkage of sweet potato based on computer vision and backscattered optical parameters is affected by the product thickness, drying temperature and drying time. A multilayer perceptron (MLP) artificial neural network with input layer containing 3 cells, 2 hidden layers (18 neurons), and 5 cells for output layer, was used to develop a model that can monitor, control and predict the shrinkage parameters and moisture content of sweet potato slices under different drying conditions. The developed ANN model satisfactorily predicted the shrinkage and dimensionless moisture content of sweet potato with correlation coefficient greater than 0.95.Therefore, combined computer vision, laser light backscattering imaging and artificial neural network can be used as a non-destructive, rapid and easily adaptable technique for in-line monitoring, predicting and controlling the shrinkage and moisture changes of food and agricultural crops during drying.

Pub.: 02 Aug '17, Pinned: 16 Apr '18

Modelling the mid-infrared drying of sweet potato: kinetics, mass and heat transfer parameters, and energy consumption

Abstract: This study investigated the drying kinetics, mass and heat transfer characteristics of sweet potato slices (0.4–0.6 cm thickness) during drying based on mid-infrared experimental set-up (intensity of 1100–1400 W/m2). Thin layer drying models were used to evaluate the drying kinetics of sweet potato slices. Two analytical models (Fick’s diffusion model, and Dincer and Dost model) were used to study the mass transfer behaviour of sweet potato slices with and without shrinkage during mid-infrared drying. The heat transfer flux between the emitter and sweet potato slices was also investigated. Results demonstrated that an increase in infrared intensity from 1100 W/m2 to 1400 W/m2 resulted in increased in average radiation heat flux by 3.4 times and a 15% reduction in the overall drying time. The two-term exponential model was found to be the best in predicting the drying kinetics of sweet potato slices during mid-infrared drying. The specific heat consumption varied from 0.91–4.82 kWh/kg. The effective moisture diffusivity with and without shrinkage using the Fick’s diffusion model varied from 2.632 × 10−9 to 1.596 × 10−8 m2/s, and 1.24 × 10−8 to 2.4 × 10−8 m2/s using Dincer and Dost model, respectively. The obtained values of mass transfer coefficient, Biot number and activation energy varied from 5.99 × 10−6 to 1.17 × 10−5 m/s, 0.53 to 2.62, and 12.83 kJ/mol to 34.64 kJ/mol, respectively. The values obtained for Biot number implied the existence of simultaneous internal and external resistances. The findings further explained that mid-infrared intensity of 1100 W/m2 did not significantly affect the quality of sweet potato during drying, demonstrating a great potential of applying low intensity mid-infrared radiation in the drying of agricultural crops.

Pub.: 04 Apr '18, Pinned: 16 Apr '18

Recent advances of novel thermal combined hot air drying of agricultural crops

Abstract: Publication date: Available online 30 September 2016 Source:Trends in Food Science & Technology Author(s): Daniel I. Onwude, Norhashila Hashim, Guangnan Chen Background Developing an efficient drying system with combined novel thermal and conventional hot-air drying of agricultural crops has become potentially a viable substitute for conventional drying techniques. Due to the synergistic effect, the total energy and time required can be drastically reduced, and the final quality of agricultural crops preserved. The growing interest and research in recent years have already shown that novel thermal with hot-air drying technology can adequately be used in the drying of agricultural crops. Scope and Approach This review attempts to give a summary of recent advances in the research and applications of novel thermal combined hot-air drying technology for agricultural crops, with particular emphasis on the combination mode, process conditions, process-quality interaction, drying kinetics, energy demand and drying efficiency. Key Findings and Conclusions The combination of novel thermal with hot-air drying provides distinctive opportunities in the development of advanced agricultural crop drying technologies. The most significant advantages of using the above method were the reduction in the drying time and energy consumption as well as, an increase in the drying rate and overall efficiency. More so, the application of infrared and hot-air drying on agricultural crops is advantageous in obtaining dried products of better quality. In conclusion, the findings suggest that these technologies have great potentials. Therefore, more study, especially in their industrial and commercial application are indispensable.

Pub.: 04 Oct '16, Pinned: 16 Apr '18

Modeling the Thin‐Layer Drying of Fruits and Vegetables: A Review

Abstract: The drying of fruits and vegetables is a complex operation that demands much energy and time. In practice, the drying of fruits and vegetables increases product shelf‐life and reduces the bulk and weight of the product, thus simplifying transport. Occasionally, drying may lead to a great decrease in the volume of the product, leading to a decrease in storage space requirements. Studies have shown that dependence purely on experimental drying practices, without mathematical considerations of the drying kinetics, can significantly affect the efficiency of dryers, increase the cost of production, and reduce the quality of the dried product. Thus, the use of mathematical models in estimating the drying kinetics, the behavior, and the energy needed in the drying of agricultural and food products becomes indispensable. This paper presents a comprehensive review of modeling thin‐layer drying of fruits and vegetables with particular focus on thin‐layer theories, models, and applications since the year 2005. The thin‐layer drying behavior of fruits and vegetables is also highlighted. The most frequently used of the newly developed mathematical models for thin‐layer drying of fruits and vegetables in the last 10 years are shown. Subsequently, the equations and various conditions used in the estimation of the effective moisture diffusivity, shrinkage effects, and minimum energy requirement are displayed. The authors hope that this review will be of use for future research in terms of modeling, analysis, design, and the optimization of the drying process of fruits and vegetables.

Pub.: 04 Feb '16, Pinned: 16 Apr '18