Abstract
Attiéké, made from biofortified (yellow) cassava genotypes, requires a new cooking method to minimize carotenoid degradation during processing. Thus, this research is aimed at designing and building a more efficient steamer to produce high-quality attiéké from biofortified cassava roots. Using three improved biofortified cassava genotypes (IBA141092, IBA070593, and IBA011368) obtained from IITA research farms, attiéké samples were produced using traditional and developed steamers. The results show that the developed steamer outperformed the traditional steamer; it was 1.5 times faster, used less fuel (2.6 times less), and had higher true carotenoid retention. The developed steamer genotype IBA070593 had the highest true retention of 90.4 percent, while the traditional steamer genotype IBA0141092 had the lowest carotenoid retention of 61.9 percent and the highest in the developed steamer (62.4 percent). When compared to the traditional steamer, the developed steamer had better cooking performance and a more extraordinary ability to retain carotenoids. Thus, the developed steamer is recommended for attiéké processors due to its improved cooking performance, and using this steamer to produce attiéké from biofortified cassava will help to alleviate vitamin A deficiency among attiéké consumers.
1. Introduction
When cassava is dried to a powdery extract called tapioca, it can be made into various products, including garri, which is fried and granular, and attiéké, which is steam-cooked. Attiéké is a traditional dish from Côte d’Ivoire. Three ethnic groups (Adjoukrou, Alladjan, and Ebrie) prepared massive amounts of attiéké for supply to Abidjan [1]. Attiéké preparation is becoming more popular in other parts of Côte d’Ivoire, as well as other countries in West Africa [2–4] and Europe. There is no recent data on attiéké consumption. However, Aboua et al. [5] estimated attiéké consumption to be between 28 000 and 34 000 tons per year, the equivalent of 40 000-50 000 tons of fresh cassava by small-scale channels, resulting in changes in production from family to commercial type [6, 7]. Gelatinization of granulated starch is a significant change that occurs during the steaming process and affects the texture and color of foods, particularly attiéké, from start to finish. A nonbiofortified cassava root without vitamin A has always been used to make attiéké. In collaboration with national partners, the International Institute of Tropical Agriculture (IITA) addressed the significant public health problem of vitamin A deficiency (VAD) by developing biofortified cassava genotypes with the biointroduction of carotenoids in the roots in the form of β-carotene [8]. On the other hand, using high heat during the processing of biofortified roots has been shown in studies to degrade and reduce the quality and quantity of carotenoids in cassava-based products [9]. As a result, attiéké made with biofortified (yellow) cassava genotypes will require a new cooking method to prevent vitamin degrading or reduction during processing. This study looks into steaming, a very gentle cooking method to prevent vitamin loss during cooking. The healthiest cooking method is steaming. It is also environmentally friendly [10]. Fang and Chinnan [11] developed a kinetics model for cowpea starch gelatinization and discovered that water diffusion and time during steaming influence starch gelatinization. The same is true for cassava starch gelatinization. Stapley and Landman et al. [12] simulated whole wheat grain steaming. They discovered that the best conditions for steaming are when heat is efficiently conducted away from the grains through contact with the metal cooker’s walls rather than contact with other grains alone.
Furthermore, researchers have worked to improve the production and storage of attiéké, as well as its nutritional value and sensory properties [4, 13, 14]. Several types of research on steaming are being considered, including how to improve its properties and the effects on the quality/preference of attiéké production in Côte d’Ivoire. The consumption of attiéké is becoming more popular. The traditional method of processing attiéké must be upgraded to meet the increased demand. The traditional steaming method has three fundamental flaws: it is time-consuming, it is labor-intensive, and the product’s quality attributes vary greatly [15]. Little research has been done into developing a pilot steam cooker to test carotenoid retention in yellow (biofortified) cassava products. The production of attiéké from biofortified cassava will benefit consumers’ health. Studies have shown processing to degrade and reduce the quality of carotenoids in cassava-based products [16, 17]. This investigation is aimed at creating a steam cooker for maximum carotenoid retention in biofortified cassava products like attiéké.
Creating an energy-efficient, cost-effective, and simple steaming facility would help reduce the labor associated with the traditional cooking of high-quality attiéké. This paper is aimed at designing and testing a steamer powered by a renewable energy source using locally available materials. The goal is to optimize the steam cooker for biofortified cassava roots by improving conventional steam cookers found in Côte d’Ivoire (Figure 1).
(a)
(b)
2. Materials and Method
2.1. Design of the Steam Cooker and Dimension Calculations
An interactive field trip was taken to processing centers in Côte d’Ivoire to understand the processing techniques and streaming methods better. The data gathered during the trip was compared to what was available in the literature. Based on the observations made during the trip, a cylindrical design was chosen for the new steamer (Figure 2). The steam cooker was designed and built in this manner. Figures 3 and 4 show the steamer’s dimensions and an exploded view.
The cooking time of the steamer, production cost, material availability, and carotenoid retention in attiéké were all studied.
The steamer’s design analysis was carried out based on the necessary parameters for functionality, the strength of the materials, and the careful selection of the various components. Each compartment of the steam cooker was measured with the actual calculations based on the following assumptions: the cooking, water, and heating chambers are cylindrical. The shape was assumed to be cylindrical as most cooking utensils are of that kind of shape to make it easy to handle. The diameter was assumed to be around 30 cm to 80 cm for easy handling by both human hands. The total height of the cooker was to take care of the reach of the average human body for handling and watching/observing inside. Other assumptions were as follows: (i)Unlike traditional cookers, the cooker should be able to steamed-cook the attiéké quickly(ii)The cooker should be made with readily available materials(iii)The cooker should be able to retain carotenoids in attiéké better than the traditional cookers(iv)The cost of the cooker should be affordable to the processors
All these were used as guides during the calculations.
2.1.1. Steamer Volumes
The pot shape and volume of the cooking pot, water pot, and heating chamber were among the assumptions. The volume was calculated using the shape volume formula as shown below:
where is the radius of the component (diameter/2) and h is the height of each component, respectively. In cases where the component must be filled to two-thirds, only adjustments were made. Measurement of each compartment makes up the steam cooker.
Thus, (a)The total volume of the steam basket (cooking pot)
Assuming we leave of the total volume of the steam basket as a free space for swelling of the mash during steam cooking to form the attiéké
The volume of the mash steam basket can accommodate is 27 771.5 cm3. (b)The total volume of water in the chamber (steam generation chamber)where is the radius of the water can () and is the height of the water.
The volume does not depend only on the volume of the attiéké mash but also (and more importantly) on the quantity of energy (heat) to be transferred from the steam to the attiéké to achieve complete cooking. (c)The total volume of the charcoal/briquette combustion chamber(d)The total volume of ash can
2.1.2. Heat Requirement
The amount of heat required to accomplish the cooking operation of attiéké was calculated by using Equations (7)–(12): The amount of water that is present in a material affects its thermal properties because these properties are functions of moisture content [18]. (a)Energy required for cooking 1 kg of mash to produce attiékéwhere is the amount of energy required (kJ). is the mass of mash (kg). is the specific heat capacity of mash (kJ/kg °C). is the initial temperature of mash before steam cooking (°C). is the final temperature of attiéké to be attained (°C).
We assumed that the amount of water in a material affects its thermal properties because these properties are functions of moisture content [18]. However, the specific heat capacity of the mash was based on the report by Alain et al. [19], who studied the physical properties of cassava mash and came about with the specific heat capacity of cassava mash before and after cooking. (b)Energy required for evaporating water to generate steam (vaporization of water)where is the amount of energy required (kJ). is the mass of water (kg). is the latent heat of vaporization of water (kJ/kg °C). (c)Energy required for heating the water to boiling pointwhere is the amount of energy required (kJ). is the mass of mash (kg). is the specific heat capacity of water (4.187 kJ/kg °C). is the initial temperature of water (°C). is the final temperature of water (°C). (d)Energy required for heating up the water can
where is the amount of energy required (kJ). is the mass of water (kg). is the specific heat capacity of stainless steel (0.510 kJ/kg °C). is the initial temperature of water (°C). is the final temperature of water (°C).
The total energy required to accomplish the cooking operation of attiéké
Assuming the loss is 1/3 of the required energy for cooking.
Loss , and the cooking time has to be limited to 1 hour maximum.
Therefore, the total design energy required for cooking 1 kg of attiéké
Steam consists of latent heat.
Hence, taking the average energy required to cook 1 kg of .
Assuming the maximum temperature achieved to be 150°C and average temperature =145°C, then pressure =415.68 kpa and enthalpy of steam for :
2.1.3. Calculation of the Thickness of Each Compartment’s Cylindrical Wall That Makes Up the Steam Cooker: The Upper Container and the Cooking Pot (Steam Basket)
The cylindrical wall was subjected to the internal pressure of the steam and the weight of attiéké. The internal pressure acting on the long sides of the cylinder would give rise to circumferential stress in the wall of the cylinder. Thus, the circumferential stress was estimated using the equation below: where is the tensile stress, is the pressure, and is the thickness.
The average tensile stress for stainless steel is 63.3 MPa [20]. The diameter of the cooking pot was calculated to be 0.25 m. The steam enters the cylinder at a pressure of 50 psi.
Therefore, the thickness of the cylindrical wall to tolerate the pressure of the steam was calculated as follows:
Therefore, the minimum thickness required m.
Table 1 shows the data on the steamer dimensions (steamer cooker cover, steam basket, etc.) obtained from the abovementioned calculations.
2.2. Material Selection for Steamer Fabrication
The following materials were used for the fabrication of the steamer: (a)Stainless steel plate: the stainless steel plate (review SS 316) is for constructing chambers directly from the food. It is one of the preferred sterile surfaces for preparing foods and is exceptionally simple to clean. Its gripping surface has no pores or splits to harbor soil or microscopic organisms. It is exceptionally alluring and requires minimal care since it does not rust easily. It will not affect the flavor because it does not respond to acidic foods during food preparation or cooking [21](b)Mild steel plate: a mild steel plate was used for the charcoal and ash cans, the chimney pipe, and the metal cap, while a angle iron was used for the stand, consisting of four legs, each 40 cm long(c)Fasteners: they were used to couple the components together(d)Mild steel and stainless electrodes: they were used during the welding process. Bolts and nuts had a threading diameter of 10 mm. A bellow was constructed to aid the combustion of the charcoal/briquette through a blast of air(e)Nonpolar solvent: the purpose of the solvent is to wash and clean the metal parts, which have been covered with oil and dust/debris and later washed with soap and pressurized steam(f)Iron wire brush: this was used to brush off the dust from metal surfaces (especially the metal frame) and prepare the surfaces for painting(g)Paint: Silver paint was used to coat, protect, and add lustre to the metal framework of the steam cooker(h)Brush: a brush was used to apply paint to the steam cooker’s surface
2.3. Evaluation of the Developed Steamer
The evaluation of the steamer for attiéké production was carried out at the Postharvest Engineering Unit of Facility Management Services (FMS) at IITA, Ibadan, Nigeria.
2.3.1. Source of Genetic Material
The cassava yellow-fleshed roots used in this study were three genotypes (IBA-011368 (sample 1), IBA-141092 (sample 2), and IBA-070593 (sample 3)) each of age 12 months. They were obtained from the Cassava Breeding Unit of the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria.
2.3.2. Other Materials
All chemicals and reagents used are of analytical grade.
The following devices, apparatus, and equipment were used for carrying out all tests necessary in the steamer. (i) Thermocouples and digital thermometers were used to measure the temperature of the combustion chamber (hot gas). (ii) Weighing balance is used to measure all weights required. (iii) Thermometer is used to measure the temperature of the water. A digital dry bulb thermometer was used. (iv) Flexible metal rule was used to measure the metal plate for fabrication and dimension of the components of the steamer. (v) Stopwatch was used to measure the time required for boiling water, attiéké steaming, and charcoal combustion.
The three genotypes were processed to produce attiéké using the constructed steamer and a traditional steamer using the method described by Alfred et al. [22].
The improved steamer (Figure 2) was evaluated for water boiling and steaming, and the results recorded were used to compute the universally accepted indices of steamer performance as shown in Equations (16) and (17):
The equation above can be expressed as where is the firepower, is the time elapsed in minutes, and is the mass of wood burnt.
The specific fuel consumption (SC) for a steamer given by Krist-Spit and Sluimer [23] is the ratio of the total quantity of charcoal used in the cooking process to the amount of water used. For a steamer, the percentage of heat utilized may be defined as the percentage of heat released by the fire absorbed by the water in the water, as shown in Equation (18). where is the percent heat utilized; is the initial mass of water; is the initial temperature of water; is the final temperature of water; is the final mass of water; is the mass of fuel burnt.
Specific heat of kJ/kg and latent heat of vaporization of water at atmospheric kJ/kg. The moisture content of the wood was 7.0%, while that of charcoal, the by-product of the combustion of wood, was 4.1%. The calorific value of fuelwood was determined as 18 400 kJ/kg, and that of charcoal was 27 600 kJ/kg.
2.4. Carotenoid Analysis Using High-Performance Liquid Chromatography (HPLC)
The carotenoid analysis was carried out using the method described by Maziya-Dixon et al. [24]. The HPLC system (Water Corporation, Milford, MA) comprised a C30 YMC carotenoid guard column ( mm, 3 μL), binary pump (Waters 626), autosampler (Waters 717), and photodiode array detector (Waters 2996). The mobile phase consisted of methanol (980 mL) with chloroform (20 mL), a flow rate of 2.0 mL/min, and an injection volume of 75 mL. The samples were examined at a wavelength of 450 nm. The total carotenoid content (TCC) was calculated using Equation (19). where is the absorbance, is the total extract volume, is the sample weight, and is the carotene extinction coefficient in petroleum ether.
The carotene content was calculated using Equation (20). where is the carotenoid peak area, is the standard concentration, is the standard area, is the total extract volume, and is the sample weight.
The methods and formula of Murphy et al. [25] and Rodriguez-Amaya [17] were used for the true retention (TR) estimation.
2.5. Calculation of True and Apparent Retention of Total Carotenoids in Cooked Attiéké
The true and apparent retentions of total carotenoids for attiéké produced by the improved and traditional cookers were calculated using Equations (21) and (22), respectively. (i)True retention(ii)Apparent retention
2.6. Product Yield
Equation (23) was used to calculate the product yield (PY), which is the percentage mass of the product that remains after each stage and is based on the initial mass of unpeeled roots (100 percent).
2.7. Statistical Analysis
Analysis of variance was performed on all generated data (ANOVA). Duncan’s multiple range test was used to separate means at a 5% probability level using a computer software package IBM SPSS Statistics for Windows, Version 20.0.
3. Results and Discussions
3.1. Steaming Efficiency of Traditional and Developed Steamers
Table 2 shows the data on fuel consumption, water usage, and cooking time for the traditional and pilot steamers. The maximum temperature inside the chamber before steam production was 102°C, with boiling water at 100°C. The steaming time difference between the developed steamer and the traditional steamer was 15, 13, and 17 minutes for samples 1, 2, and 3, respectively. However, the differences in the total cooking time taken by the developed and traditional steamers for samples 1, 2, and 3 were 35, 30, and 32 minutes, respectively, using each of its most appropriate energy source, which is wood for the traditional cooker and charcoal for the improved cooker. Thus, the developed steamer was able to cook attiéké more quickly (an average of 1.5 times faster). The fuel consumption rates of the three genotypes of roots used varied. Although the aim was not to compare wood to charcoal, it is worth noting that the study showed that the developed steamer consumed 3.3 kg of charcoal to cook attiéké for 1 h 10 min in sample 1 (Genotype 1BA-011368), while the traditional steamer consumed 6.3 kg of wood to cook attiéké for 1 hour and 45 minutes. When comparing the steamers’ fuel consumption and cooking time duration, there were differences of 3.0 kg and 35 minutes, respectively, for sample 1.
Moreover, these differences were 3.8 kg and 30 minutes for sample 2 (IBA-141092) and 4.0 kg and 32 minutes for sample 3 (IBA-070593). It could be concluded that the developed steamer consumed less of its fuel (charcoal) and cooked faster than the traditional steamer that was also using its best-suited fuel (wood) for attiéké preparation from yellow-fleshed cassava. The time-saving findings and, to some extent, the energy savings could translate to an excellent processing cost reduction for the attiéké processors with better working conditions.
Table 3 shows the performance evaluation of the improved and the traditional cookers. The improved steam cooker’s fuel firepower (fp) ranged from 31 to 41 MW, while the traditional steam cooker’s ranged from 43 to 63 MW. The improved steam cooker had a specific fuel consumption (SC) of 0.12 kg/kWh, while the traditional steam cooker had a specific fuel consumption (SC) of 0.24 kg/kW. The pilot steam cooker’s heat (PHU) ranged from 12 to 13 percent (or 12 percent-13 percent thermal efficiency), whereas the traditional steam cooker’s from 6 to 8 percent. The tests yielded a 13 percent efficiency. The improved steam cooker outperformed the traditional steam cooker by about 8%; this steamer could steam-cook attiéké in a shorter time (about 1.5 times faster), with the highest percentage of heat utilization standing at 2.6 times less fuel. We consider this steamer a prototype, and we hope to improve the improved cooker further by taking care of the materials and some dispositions (like lagging the heating chamber that was not incorporated if included, which would have decreased the heat loss on the improved cooker).
3.2. Carotenoid Content and Retention in Cooked Attiéké
The total carotenoid and β-carotene contents of fresh raw roots of the three biofortified cassava genotypes are shown in Figure 5. The highest total carotenoid and trans-β-carotene levels are found in genotype IBA-141092 (sample 2), followed by genotype IBA-070593 (sample 3). However, the levels of the cis-isomers (9-cis and 13-cis) appear the same in all three genotypes studied. The values of carotenoids obtained for these genotypes agree with what Maziya-Dixon et al. [16] obtained in the yellow-fleshed cassava genotypes grown in the same location.
However, Figure 6 also compares the total carotenoid and β-carotene contents of attiéké samples steam-cooked by the two steamers. The total carotenoids and total β-carotene contents of the cooked attiéké samples from the developed (pilot) steamer were consistently higher than that of the traditional steamer. However, considering the isomers of β-carotene, it was observed that the trans-β-carotene contents of attiéké samples from the developed steamer are higher than that of the traditional steamer across the genotypes. Nevertheless, the 9-cis and 13-cis-isomers look similar. We can conclude that the steaming process significantly impacted the trans-isomers more than the cis-isomers.
Figure 7 shows the true and apparent retention of carotenoids in attiéké produced from three selected cassava genotypes by the traditional and pilot steamers. Generally, the pilot steamer’s apparent and true retention values are higher for all three genotypes than the traditional steamer’s. Sample 3 (genotype IBA-070593) of the developed steamer had the highest carotenoid retention value, followed by sample 1 (IBA-011368). Moreover, sample 3 showed the highest carotenoid retention using the traditional steamer. The genotype IBA-070593 is a good cassava variety for producing attiéké from yellow-fleshed cassava. However, a sensory test on this sample is required to determine the most acceptable attiéké samples. Higher retention may not always be associated with acceptable sensory quality. More testing with different traditional steamers and evaluating the developed steamers with attiéké processors are recommended to determine the likelihood of acceptance of this good steamer.
3.3. Steamer Production Cost Analysis
Table 4 shows the estimated cost of materials for the developed steamer. It is an excellent idea to give the estimated cost of the developed steamer as it has been found in this study that it is more effective than the traditional method. The cost of the machine includes the cost of the materials brought to the engineering workshop and the accompanying accessories and labor. The total cost of the equipment is approximately US$630 (Table 2). The affordability of the developed steamer may be part of our future work to lower the cost below the current one, but we believe it will be affordable for small- and medium-scale attiéké processors for mass production.
4. Conclusion
A renewable energy steam cooker was built at the IITA in Ibadan, Nigeria. Its performance and carotene retention were compared to a traditional steamer using three different biofortified yellow cassava root genotypes. The study found that the constructed steamer took less time (1.5 times faster) to bring water to the boiling point and consumed less fuel (2.6 times less) than the traditional steamer while using 1.7 times less water and taking 2.6 times less time to cook the same batch. The traditional steamer retained 12.95% true β-carotene. The study also revealed that the newly built steamer outperforms traditional steamers regarding β-carotene retention and efficiency. The developed steamer is cost-effective as the price per unit is $630. We recommend that this newly constructed pilot steam cooker be evaluated and optimized, preferably in the country of attiéké itself, with professional processors, and that it be compared with the best steamers locally available. Based on the findings, some changes can be made, and the optimized steamer can be replicated at least ten times for scaling across countries. The developed steamer will be affordable and may be recommended for small- and medium-scale attiéké processors when mass-produced.
Data Availability
The data supporting the results reported in this paper are available on request from the corresponding author (e-mail: [email protected].
Disclosure
This study was presented as a poster presentation at the International Association of Research Scholars and Fellows’s (IARSAF) 22nd Annual Symposium at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this article.
Acknowledgments
This study was carried out as part of the CGIAR Research Program on Roots, Tubers, and Bananas (RTB) and was funded by the CGIAR Trust Fund contributors (https://www.cgiar.org/funders). The authors acknowledge Mr. Adesokan Michael of the IITA Food and Nutrition Sciences Laboratory, Mr. Braimoh Bamidele of IITA Facilities Management Services, and the entire attiéké processors who participated in the scoping study, preceding design, and fabrication of attiéké steamer. This study was supported with funds from the CGIAR Research Program on Roots, Tubers, and Bananas (RTB). The genetic materials were provided by HarvestPlus. The APC was paid by the NextGen Project.