This study involves development and multiobjective analysis of an integrated milling and sieving machine for Bambara flour production. This will improve hygiene and reduce excessive drudgery and food loss in this sector thereby aiding mass production of quality bambara flour at low cost. Its major components include: electric motor, flour and chaff discharging chutes, turbo-pneumatic sieve and hammer mill. Performance of this machine was empirically evaluated and quantified using response surface design and models at two levels of factors while desirability optimization and benefit cost methodologies constitute the optimization and investment analysis techniques applied in this investigation. Performance analysis results revealed Bambara grains’ moisture content, number and speed of cross beaters and paddles as these machine process/operational parameters (factors) with significant influence on its performance while throughput and extraction efficiency constitutes its functional performance indicators (responses). The cross beater and grains’ moisture content affect the particle size of the milled grain directly while sieving (extraction) of the grain food/starch granules (flour) from its fibre (chaff) depends on this particle size and paddle parameters. In addition, the multi-response performance simulation of this machine predicted 12.05%, 6, 4, 1610rpm and 1038rpm as the grain moisture content, number of cross beaters and paddles, cross beater and paddle speeds require for its optimal operation with over 98% accuracy. The machine performs with throughput and extraction efficiency of 117.8kg/h and 98.45% respectively at these optimal factor settings. Experimental evaluation revealed 41.15kg/h and 84.18% as the average throughput and extraction efficiency of semi-mechanized Bambara flour processing system. Thus, the novel Bambara nut milling-sieving machine for Bambara flour production reduced the food loss to chaff in this sector to 1.55% against 15.82% associated with the widely used semi-mechanized system. It also promotes hygiene in this sector because it eliminated human contact with the milled grain during sieving. The cost-benefit analysis of this machine showed that it is viable economically because of its positive capital recovery potentials. The machine’s payback period of 1.5years is far less than its useful life of 10years, while its 46.89% accounting rate of return outweighed Nigerian banks maximum fixed deposits return of 17% and prime lending rate of 29%. Therefore, general adoption of the integrated milling and sieving machine developed in this study is recommended for Bambara flour processing.
TABLE OF CONTENTS
Title page i
Table of Contents vi
List of Tables vii
List of Figures viii
List of Plates ix
CHAPTER 1: INTRODUCTION
1.1 Background of Study 1
1.2 Statement of Problem 3
1.3 Aim and Objectives of the Study 5
1.4 Scope of the Study 6
1. 5 Justification of the Study 6
CHAPTER 2: LITERATURE REVIEW
2.1 Overview of Bambara Processing Technologies 7
2.1.1 Traditional processing method 7
2.1.2 Mechanized Bambara flour processing systems 8
2.2 Mechanized Grain Flour Sieving Systems 18
2.3 Multiobjective Systems Optimization with Response Surface Methodology 21
2.4 Cost-Benefit Based Machinery Investment Analysis 28
CHAPTER 3: MATERIALS AND METHODS
3.1 Materials 31
3.2 Design Methodology and Analysis of Bambara Processing Machine 31
3.2.1 Description of Bambara flour processing machine 31
3.2.2 Design concept/considerations of Bambara processing machine 33
3.2.3 Design of Bambara flour processing machines sieving process 34
3.2.4 Design/selection of power transmission systems of the machine 38
3.2.5 Power rating/selection of the machines prime mover 41
3.3 Performance Analysis Procedure for Bambara Flour Processing Machine 42
3.3.1 Factors screening procedure 42
3.3.2 Multifactor-response evaluation and modeling procedure 43
3.3.3 Multi-objectives simulation and optimization procedure 46
3.3.4 Comparative analysis procedure for bambara flour processing machine 48
3.4 Cost-Benefit Analysis Procedure for Bambara Flour Processing Machine 49
CHAPTER 4: RESULTS AND DISCUSSION
4.1 Empirical Analysis of Bambara Flour Processing Machine 51
4.2 Performance Modelling of Bambara Flour Processing Machine 58
4.3 Multi-response Simulation and Optimization of the Machine 69
4.4 Comparative Analysis of the Machine with Semi-Mechanized Process 72
4.5 Economic Analysis of Bambara Flour Processing Machine 75
CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 80
5.1.1 Contributions to knowledge 81
5.2 Recommendations 82
LIST OF TABLES
3.1 Factorial design layout for evaluating main effects of the
Bambara flour processing machine 43
3.2 Response surface design layout for non-linear simulation of the
Bambara flour milling-sieving machine 45
4.1 Functional limit of grain moisture content and cross beaters 51
4.2 Multifactor evaluation of particle size of flour processed with this machine 52
4.3 Analysis of variance for the quadratic model of the flour particle size 55
4.4 Coded coefficient 55
4.5 Functional limit of particle size of flour and paddle 58
4.6 Multiobjective evaluation of Bambara flour processing machine 58
4.7 Coded coefficient of throughput and extraction efficiency 59
4.8 Fit statistics for main effect response models of Bambara processing machine62
4.9 Analysis of variance for the Bambara processing machine 62
4.10 Coded coefficients of throughput and extraction efficiency 63
4.11 Fit statistics for main effect quadratic response models of Bambara
processing machine 67
4.12 Analysis of variance for the quadratic model of the throughput
and extraction efficiency 68
4.13 Comparison of the experimental and fitted value of the response 69
4.14 Experimental analysis of semi-mechanization of Bambara processing 72
4.15 Experimental analysis of Bambara processing machine 73
4.16 Comparison of the experimental throughput and efficiency to the
Predicted throughput and efficiency 74
4.17 Salvage value of the Bambara flour processing machine 77
4.18 Analysis of nonrecurring and recurring annual costs and revenues
of integrated Bambara Processing Machine 77
4.19 Analysis of Present Value Costs and Benefits of
bambara nut milling and sieving machine 78
4.20 Net Cash Flow Analysis of Machine before tax 80
LIST OF FIGURES
1.1 Structure of the Bambara nut seed. 1
1.2 Operational sequence of bambara flour processing 2
2.1 Conventional bambara groundnut processing method 9
2.2 Microwave vacuum dryer 11
2.3 Bambara nut decorticating machine 12
2.4 Bambara nut decorticating machine 13
2.5 Hammer mill 16
3.1 Bambara flour processing machine 35
3.2 Machine Frame with dimensions 32
4.1 Main effect plot on factors of factors on milled bambara particles 53
4.2 Residual plot on bambara flour particle size 54
4.3 Experimental analysis of prediction accuracy of the bambara flour particle size function 54
4.4 Desirability simulation plot of the bambara flour particle size function 56
4.5 Main effect plots of throughput 60
4.6 Main effects plot for extraction efficiency 60
4.7 Residual plots of the throughput main effect 61
4.8 Residual plots of the extraction efficiency main effect 61
4.9 Residual plots of the quadratic model for throughput 66
4.10 Residual plots of the quadratic model for extraction efficiency 66
4.11 Confirmatory test for extraction efficiency 67
4.12 Optimization plot for the performance parameter model 72
LIST OF PLATES
2.1 Manual grinding machine with an auger 14
2.2 Single-stage burr mill 14
2.3 Continuous multi-stage grinder 15
2.4 Traditional sieving method 18
1.1 BACKGROUND OF STUDY
Bambara seed is a crop with a high potential for the attainment of food security and poverty alleviation in Nigeria and Africa at large, as it shows considerable drought resistance and potentially high nutritional qualities (Yusuf et al.,2008; Atoyebi et al., 2017). The bambara seed as shown in Fig 1.1 consist of edible endosperm, covered with thinner coat, housed in a pod.
Fig. 1.1: Structure of bambara seed
According to Orhevba et al. (2016) bambara seed is a completely balanced food because it is very rich in iron, protein, ash, fat, fibre, potassium, sodium, calcium, carbohydrate, oil and energy. Atoyebi et al. (2017) further showed that its protein content is of superlative best worth and has over plus lysine which complements cereals in the diet unlike other grains. Bambara seed according to Jagdev (2018) is rich in beneficial bacteria known also as probiotics, milk from bambara seed is used for therapeutic purposes in diarrhoea and irritable bowel syndrome. Thus it has diverse application in human diet such as pudding/porridge, relish, pastries, flour and food thickener. The operational sequence involved in bambara flour processing as shown in Fig.1.2 involves the following processes: washing, drying, decorticating, milling and sieving.
Fig 1.2: Operational sequence of bambara flour processing
Drying of bambara seed according to Yusuf et al. (2008) involves application of heat to reduce moisture content of the seed for effective decorticating and milling of the seed to flour. Decorticating involves the opening of the pods by either cracking it with a stone, stick to enhance milling operation.
The quest for mechanized bambara seed processing system cannot be over emphasized as a result of drudgery and unhygienic nature of the traditional/manual processing. Hence, the innovation of bambara pod decorticating machine which addressed decorticating of the pods was successfully developed and improved upon by Adedeji and Danladi (2016) and Eze, (2016). Successful milling was also achieved through petrol- powered hammer milling machine as developed by Adekomaya and Samuel, (2014). Ground bambara flour consist of some unwanted or coarse particles bounded together with the fine particles after milling operation which can be separated by sieving. This process is necessary to separate fine flour of ground bambara flour from the fibrous content of the seed and unwanted coarse flour resulting from insufficient milling operation. Sieving which involves separating the fine flour of the ground bambara seed from its fibrous content (chaff) is yet receiving adequate attention for mechanization. This is because bambara seed is hard and impermeable with strong binding property unlike other seeds such as soybean and cowpea (Juliet et al., 2017). As a result manual sieving is witnessed and generally adopted by processor in this sector as the only means of separating the fine bambara flour from its fibrous content. Since Hillock et al. (2011) revealed its high demand as a result of the unique content, unique taste, flavour and enhanced iron, calcium, phosphorous, magnesium, zinc and copper content also the level of these minerals were higher than those found in commonly consumed legumes. The unsuccessful mechanization of the bambara nut milling and sieving processes was also attributed to its negative ‘hard-to-cook’ trait by Mayes et al. (2019). Suqin et al. (2007) and Mubaiwa et al. (2017) showed high binding force between the bambara nut’s coat and cotyledon due to its phenolic compound content and lack of inherent crack in seed coat as the cause of this negative trait of bambara nut because they makes the nut impermeable to water, heat and chemical. Therefore, the need for a processing method/system that can tackle this trait effectively to enable continuous milling and sieving operation.in bambara flour production, thereby, positioning bambara groundnut adequately for mitigating future food and nutritional challenges in line with Khan et al. (2021).
1.2 STATEMENT OF PROBLEM
The multiple stage milling and lack of mechanization of the sieving process of bambara flour extraction from its seed remain a holdup for the processor because the seed contents of lipid and crude lipid similar with soybean seed resulting in difficulty in their seed coat separation from the cotyledon after milling. However, the seed coat of soybean according to Suqin et al. (2007) can be separated by soaking in water, roasting or by dipping in CHCL3 before milling. This is because soybean contains hydroxyl fatty acids and anatomical study also revealed that the only features consistently correlating with the seed permeability to water is inherent small cuticle cracks on the surface of the seed coat as stated by Suqin et al. (2007). This is not so with bambara seed coat. Bambara seed coat is impermeable to water, heat and chemical because it does not contain inherent cracks like the soybean seed (Suqin etal., 2007). In addition, Mubaiwa et al. (2017) showed that bambara seed contains phenolic compound such as lignin, tannin and hydroxycinnamic acid as well as phytase-phytate-pectin unlike other grains. This is therefore a justification for the high strength of binding force witnessed between the coat and the cotyledon of the seed.
Lignin which is contained in bambara seed according to Neeraj etal. (2017) serves as coatings, agricultural chemicals, micronutrients, natural binders, adhesives, resins and in the manufacturing of vanillin and textile dyes. Owing to its huge chemical structure, lignin can as well provide additional functionality such as filler, reinforcing agent, compatibilizer, stabilizer as well as fire retardant (Neeraj et al., 2017). Tannin acts as grout or extender to participate in the formation of adhesive bond and stiffness (Hussein et al., 2011). Also phytase- phytate-pectin when heated in the presence of liquid expands and turns into gel, making it a great thickener for jams and jelly (Savanna and Adda, 2019). Thus, these combined binding characteristics of bambara seed content, and its resistance to water and heat, increases the strength of the bond when subjected to destructive process like heating. As a result, manual sieving is predominant in this sector as the only method of separating chaff from the fineness flour. Further investigations on the manual sieving process reviewed that 30minutes to one hour is set aside to allow the temperature of the ground flour discharged from the mill which is over 600C to decrease to about 400C, beforehand stirring of the flour could be done. This is to prevent inflicting injury on the operator since the operator is the source of power (human hands). The human hands in manual sieving operation serve two purposes which include; compressing and shearing of the ground bambara flour against the sieve. This results in fine flour sipping through the sieve apertures to the receptacle while retaining the coarse unwanted particles which will be discarded after each batch of sieving. This compressing and shearing is done with about 50 moves per minutes in an anti-clockwise and corresponding clockwise rotational movement of the right and left hand followed by regular tapping on the sieving surface. This is done in order to overcome the binding force by physical process. Therefore the need to improve the milling section to eliminate multiple milling and mechanize the manual process of sieving by developing a system which harnesses the force of air generated from the milling system with the help of a rotational device at the sieving chamber to overcome the binding force of the bambara seed coat and the cotyledon through mechanized process.
1.3 AIM AND OBJECTIVES OF STUDY
The aim of this study is development and parametric analysis of bambara flour processing machine using response surface methodology. The specific objectives include.
1. Design of a pneumatic process based sieving machine for separating food starch granules of milled bambara grain from its fibrous seed coat chaff.
2. Development and integration of the sieving machine to an improved hammer mill for continuous milling and sieving operations in bambara flour production.
3. Empirical evaluation and modeling of this integrated milling and sieving machine’s performance using response surface methods.
4. Determination of its optimal operational parameters using response surface based desirability optimization methodology.
5. Evaluation of this integrated machine’s economic viability using cost-benefit methodologies.
1.4 SCOPE OF STUDY
This work covers design, development, performance characterization, modelling, optimization and investment analysis of an integrated milling and sieving machine for bambara flour production.
1.5 JUSTIFICATION OF STUDY
Development of the sieve and its integration with cross beater hammer mill to enable continuous milling-sieving process during bambara flour production is of interest and relief to both small and medium scale bambara flour processors. This is because it aids mass production of quality bambara flour at low cost thereby boosting income, food security and employment in this country. This innovation reduced flour lost to chaff and improved the processing hygiene through elimination of drudgery and human contact involved during loading/discharging of intermediate processed flour among the unit operations. Application of multifactor-response surface methodology simulation in this study enabled the establishment of optimal operational parameters of the single flow process bambara flour processing machine with small number of experimental runs. The cost benefit analysis of the machine provided adequate details of its economic/investment viability to guide and encourage prospective investors in this lucrative sector.
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