ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT AZOJETE December 2022. Vol. 18(4):707-720 Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2644, Electronic ISSN: 2545-5818 www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 707 ORIGINAL RESEARCH ARTICLE MOISTURE AND TEMPERATURE INFLUENCE ON THERMAL PROPERTIES OF WINGED BEAN (Psophocarpus tetragonolobus) SEED ACCESSIONS K. O. Oriola1, J. B. Hussein2*, M. O. Oke3 and R. D. Isiaka1 1Departement Agricultural Engineering, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria 2Department of Food Science and Technology, Modibbo Adama University, Yola, Adamawa State, Nigeria 3Department of Food Engineering, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria. *Corresponding author’s email address: jbhussein01@mau.edu.ng 1.0 Introduction Winged bean (Psophocarpus tetragonolobus (L.) seeds are tropical crops listed as under- exploited legumes, notwithstanding their high yield potential and nutritional value compared with soybean (Vatanparast et al., 2016; Adegboyega et al., 2019). Winged bean is a crop with several uses; it can be grown as a pulse, root, and tuber crop. Every part of the plant contains distinct nutritional constituents. The leaves and pods are rich sources of vitamins, minerals, and fibre; the seeds are high in protein, while the tubers are rich sources of carbohydrates (Wong et al., 2015; Vatanparast et al., 2016; Adegboyega et al., 2019). The winged bean seed contains high dietary protein due to its amino-acid contents, considerable protein bioavailability, and low anti-nutritional factors (Wan Mohtar et al., 2014). Depending on the accessions and agro-climatic conditions, the seeds have a high range of crude protein (28.43-36.6%), crude fat (13.87-19.01%), ash (4.55-4.98), and carbohydrate (18.43-37.82), as reported by Adegboyega et al. (2019). The seeds also contained a high proportion of phosphorus, calcium, magnesium, zinc, sodium, and copper (Lepcha et al., 2017). Because ARTICLE INFORMATION ABSTRACT The thermal properties of three winged bean seed accessions (Entry 4 Tropical Psophocarpus tetragonolobus (TPT) 6, Entry II Tropical Psophocarpus tetragonolobus (TPT) 30, and Entry 12 Tropical Psophocarpus tetragonolobus (TPT) 32) at 5, 10, 15, 20, and 25% moisture contents and 30, 40, and 50 ᵒC temperatures were determined with the KD2 Pro Thermal Analyzer. The results showed that the thermal properties of the seed accessions were moisture-temperature dependent. Entry II TPT 30 had the highest specific heat capacity (1.37-2.59 kJ.kg-1K-1), while Entry 4 TPT 6 had the highest thermal conductivity (0.17-0.60 W.m-1K-1) and thermal diffusivity (0.19-0.77 x 10-7 m2.s-1) as the temperature and moisture increased. A second-order polynomial model described the relationship between the moisture, temperature, and the three thermal properties studied. Respective high correlation coefficients (R2 ≥ 0.9126, 0.9872, and 0.9801 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32 accessions, respectively) indicated their ability to simulate these parameters within the moisture-temperature domain studied. The winged bean seeds' thermal properties will be used to guide design decisions for the creation of agricultural machinery, thermal processes, and equipment required for storage, drying, heating, and cooling. © 2022 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved. Submitted 31 January, 2022 Revised 22 June, 2022 Accepted 24 June, 2022 Keywords: thermal conductivity thermal diffusivity specific heat capacity moisture content winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):707-720 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 708 most parts of the plant are edible at all stages of its life cycle, coupled with its exceptional nutritional quality, it was taken as a promising candidate for food and nutrient security in protein-deficient areas of the world (Lepcha et al., 2017). Notwithstanding the great potential of winged bean seeds, prolonged cooking times significantly limit their utilization. Sambudi and Buckle (1991) reported that the seeds are the essential part; unfortunately, they are the least used product because they are difficult to cook and require a long cooking time for their tenderization. Some winged bean seed accessions have harsh seed coats, making water absorption difficult, while most of them have differing degrees of impermeability to water (Sambudi and Buckle, 1991). Ojo and Ade- Omowaye (2015) also reported certain anti-nutritional compounds such as enzyme inhibitors, hemagglutinins, cyanogens, phytic acid, apart from prolonging cooking time. Oligosaccharides, saponins, and tannins are other factors preventing the efficient utilization of leguminous crops. Thus, the need for intensive heat for cooking wing bean seeds and cracking processes. The thermal properties are essential in various handling and processing operations involving heat and mass transfer (Oriola et al., 2021). Therefore, studying the thermal properties of wing bean seeds is imperative especially for those accessions that have proved promising. Knowledge of the thermal properties of food and agricultural products is essential for quantifying some unit operations like cooling, heating, drying, pasteurization during post- harvest handling and storage processes and designing processing systems. Thermal properties of agricultural products commonly determined are specific heat, thermal conductivity, and thermal diffusivity. The property needed in the estimation of the amount of energy required to change the temperature of a given mass of product by 1oC is called specific heat, while thermal conductivity and thermal diffusivity are involved in the assessment of the rate of heat transfer for efficient process and equipment design (Yang et al., 2002; Mahapatra et al., 2013). The measure of the ability of a material to conduct heat through it is known as its thermal conductivity. In contrast, the material’s inertia, that is, the ability of a material to conduct heat relative to the heat stored per unit volume, is thermal diffusivity. Thermal conductivities are used for modelling thermal processes such as chilling, freezing, and drying, as such models allow for process optimization to improve quality and efficiency (Carson, 2017). On the other hand, the thermal diffusivity explains the heating rate (the heat penetration and temperature distribution) of grains stored in steel silos, mainly in the grain layers closest to the metal sheet, where convective currents of air are responsible for the migration of moisture and heat (Pohndorf et al., 2017). These thermal properties are important parameters to know in designing equipment or its part and, in a computer simulation, to analyze, optimize, and control the temperature during the elaboration, storage, transportation, and commercialization of foods. Research results have shown that the thermal properties of food and agricultural materials are temperature and moisture dependent (Oriola et al., 2016; Oriola et al., 2021). Also, there is much research on the thermal properties of nuts or seeds such as pumpkin seeds (Kocabiyik et al., 2009), peanut pods (Bitra et al., 2010), Roselle seeds (Bamgboye and Adejumo, 2010), baobab fruits (Adekunle et al., 2013), cowpea flour (Mahapatra et al., 2013), red lentil seeds (Gharibzahedi et al., 2013), cooked locust bean (Oriola et al., 2016), Bambara groundnuts file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng Oriola et al: Moisture and Temperature Influence on Thermal Properties of Winged Bean (Psophocarpus tetragonolobus) Seed Accessions. AZOJETE, 18(4):707-720. ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 709 (Abioye et al., 2016), soybean (Pohndorf et al., 2017), and jack bean seeds (Adeyanju et al., 2019; Oriola et al., 2020). Literature search revealed that research on moisture content and temperature effects on the specific heat, thermal conductivity, and diffusivity of winged bean seeds are sparse. The aim of this study was to investigate how temperature and moisture content affected the thermal characteristics of three accessions of winged bean seeds. 2. Materials and Methods 2.1. Samples collection Mature winged bean seed (Entry 4 Tropical Psophocarpus tetragonolobus (TPT) 6, Entry II Tropical Psophocarpus tetragonolobus (TPT) 30, and Entry 12 Tropical Psophocarpus tetragonolobus (TPT) 32) accessions were obtained from the Genetic Resources Unit of the International Institute of Tropical Agriculture (IITA) Ibadan, Oyo State, Nigeria. The seeds were manually winnowed to remove all the extraneous materials. These have been identified among the ten most promising winged bean seed accessions by the IITA. 2.2. Determination of moisture content The initial moisture content of the winged bean seed accession was determined as described by AOAC (2010) and adopted by Oriola et al. (2016). Five (5 g) of the sample was weighted with a digital electronic weighing scale (GF-6000AND, Japan) of 0.01 g accuracy. The sample was then dry in an electric oven (DHG9101.ISA, UK) at 103 ᵒC for 48 hours. After drying, the per cent moisture content in the sample was determined using the expression in Equation 1. 𝑀𝐶𝑤𝑏 = 𝑊𝑚 𝑊𝑤 × 100 (1) Where; MCwb = winged bean seed moisture content (% wet basis) Wm = weight of moisture (g) Ww = weight of the wet sample (g) The winged bean seed (100 g each) were also conditioned to five different moisture contents of 5, 10, 15, 20, and 25 % (wet basis) after determining the initial moisture content using an OAHM 60 digital moisture analyzer (MD7822 Model) as described by AOAC (2010) and adopted by Oriola et al. (2016). Next, the moisture content of each sample was increased or decreased to the required moisture contents by using either Equation 1 or 2 as appropriate. After that, the samples were poured into polyethene bags, sealed tightly, and conditioned in a refrigerator for 24 h to equilibrate the moisture contents. 𝑄 = 𝑊𝑖 (𝑋𝑓−𝑋𝑖) 100−𝑋𝑓 (2) Where: Q = Mass of water added Wi = Mass of winged bean seed Xf = Final moisture content of the winged bean seed Xi = Initial moisture content of the winged bean seed http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):707-720 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 710 2.3. Determination of thermal properties The Decagon KD2 Pro thermal analyzer that employs the transient line heat source method was used to determine the specific heat capacity (Cp), thermal conductivity (k), and thermal diffusivity (α) simultaneously, as described by Oriola (2014) and Oriola et al. (2016). The sample holder was loaded with a known quantity of the already conditioned winged bean seeds, and the SH-1 probe gang was selected and inserted through the lid of the sample holder. The reading time of 2 minutes was set for computing the thermal properties determined at an average room temperature of 30ᵒC at each moisture level. The reading displayed on the screen was taken and recorded at an error value of 0.001. After that, the needle of the SH-1 probe of the thermal analyzer rested for 15 minutes to equilibrate to the surrounding temperature before the next experiment as recommended by the manufacturer. The experiments were replicated five times at each moisture level. A thermostatic water bath (DK-2000-ISL) was used to raise the temperature of the samples to 40 and 50ᵒC, respectively, before the above experimental procedures were then repeated at these temperatures for each winged bean seed accessions. 2.4. Statistical Analysis The data collected were analyzed with SPSS® version 20 (Statistical Package for Social Sciences, USA). The Duncan’s Multiple Range Test was used to determine the significant difference between the means, and the differences were significant at p< 0.05. Microsoft Excel spreadsheet software version 2013 was used to do all the experimental calculations. Regression analyses of the experimental data were analyzed with the Stat-Ease Design Expert 11.1.2.0 software. 3. Results and Discussion 3.1. Specific heat capacity (Cp) of the three winged bean seed accessions Results of the specific heat capacity of the winged bean seed accessions were presented in Table 1. In these seeds moisture ranged, the Cp values were observed to increase steadily with an increase in moisture content of the samples for each of the three winged bean accessions, irrespective of temperature. This increase in the Cp with increasing moisture content could be due to the high specific heat of water compared to the dry material, making the water occupy the void spaces faster at lower moisture contents. The Cp values were lower than those reported for pumpkin seeds (2.53 to 3.13 kJ.kg-1K-1) by Kocabiyik et al. (2009) and peanut pod (2.1 to 3.3 kJ.kg-1K-1) by Bitra et al. (2010). However, they were slightly higher than cooked locust bean seeds (1.38 to 1.94 kJ.kg-1K-1) and jack bean seeds (1.38 to 1.89 kJ.kg-1K-1) reported by Oriola et al. (2016) and Adeyanju et al. (2019), respectively. The high Cp values obtained for the three winged bean seed accessions translates to winged bean seed requiring thousands of Joules to increase or lower the heat energy by 1 ᵒC. Table 1: Specific heat capacities of three winged bean seed accessions Temperature (oC) Moisture Contents (%) Entry 4 TPT 6 (kJ/kgK) Entry II TPT 30 (kJ/kgK) Entry 12 TPT 32 (kJ/kgK) file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng Oriola et al: Moisture and Temperature Influence on Thermal Properties of Winged Bean (Psophocarpus tetragonolobus) Seed Accessions. AZOJETE, 18(4):707-720. ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 711 5 1.44 ± 0.16c 1.72 ± 0.03bcde 1.67 ± 0.07cde 10 1.65 ± 0.10bc 1.93 ± 0.18bc 1.84 ± 0.10c 30 15 1.73 ± 0.16bc 2.09 ± 0.05b 2.26 ± 0.22b 20 2.40 ± 0.17a 2.48 ± 0.14a 2.37 ± 0.11ab 25 2.42 ± 0.03a 2.59 ± 0.13a 2.63 ± 0.07a 5 1.53 ± 0.01c 1.36 ± 0.03e 1.47 ± 0.12e 10 1.64 ± 0.10bc 1.61 ± 0.11cde 1.49 ± 0.10de 40 15 1.76 ± 0.10bc 1.67 ± 0.13bcde 1.60 ± 0.03cde 20 2.52 ± 0.17a 1.95 ± 0.13bc 1.63 ± 0.13cde 25 2.53 ± 0.15a 2.08 ± 0.21b 1.82 ± 0.07cd 5 1.38 ± 0.02c 1.37 ± 0.28e 1.34 ± 0.09e 10 1.42 ± 0.16c 1.46 ± 0.10de 1.54 ± 0.03cde 50 15 1.52 ± 0.13c 1.55 ± 0.04cde 1.59 ± 0.03cde 20 1.52 ± 0.18c 1.72 ± 0.06bcde 1.62 ± 0.03cde 25 2.00 ± 0.18b 1.88 ± 0.14bcd 1.66 ± 0.16cde Means within the same column at each temperature with different superscripts are significantly different (p<0.05) Figure 1 represents the surface plot showing the interactions between the temperature, moisture, and Cp of the winged bean seed accessions. As observed from the plots, the Cp increased linearly as the moisture content increased at a low temperature of 30 oC for the three accessions. The linearly increasing trend in Cp with moisture content correlates with work done by other researchers for other agricultural products such as; Bart-Plange et al. (2012) for cashew kernel, Mahapatra et al. (2013) for cowpea, Isa et al. (2014) for melon seeds, Abioye et al. (2016) for Bambara groundnut, Oriola et al. (2016) for cooked locust bean seeds and Matouk et al. (2018) for faba bean seeds. At a lower temperature (30 ᵒC), the percentage increases of the Cp with moisture increase were higher than those at higher temperatures (50 ᵒC) for the three accessions. This suggests that low heat energy would be needed to change the temperature of the bean seed accessions during heating processes. However, other studies have reported decreasing trends with moisture content, such as; Bamgboye and Adejumo (2010) for roselle seeds and Adeyanju et al. (2019) for jack bean seeds. This shows that the food materials to be processed would determine the type of heat processing it needs to be subjected to. Thus, these results of Cp could help analyze the heat energy required for each stage of the processing and optimization of winged bean seeds. This will, in turn, reduce the heating duration to the barest minimum, which could help in nutrients retention and energy savings. http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):707-720 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 712 Figure 1: Effects of moisture and temperature on specific heat capacities of winged bean seed accessions Several regression equations were fitted to determine the model that best describes the relationship between temperature, moisture content, and Cp of the studied winged bean seed accessions. Second-order polynomial models gave the highest coefficient of determination (R2) value of 0.9126, 0.9877, and 0.9886 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32, respectively (Table 2). This implies that these 2nd order polynomial equations obtained could best fit the relationships between temperature, moisture, and the Cp of the winged bean seed accessions studied. The model F-values of 10.43, 60.04, and 64.92 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32, respectively (Table 3), implied that the models were significant. The analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the Cp of the Entry II TPT 30 and Entry 12 TPT 32 accessions. However, effects of combined temperature and moisture content were not significant (p > 0.05) with the Cp of the Entry 4 TPT 6 accession. Table 2: Polynomial regression model equations for three winged bean seed accessions Accessions Equations R2 𝐶𝑝 = 1.930 − 0.221𝑥1 + 0.576𝑥2 − 0.137𝑥1𝑥2 − 0.256𝑥1 2 + 0.126𝑥2 2 − 0.171𝑥1 2𝑥2 + 0.081𝑥1𝑥2 2 + 0.016𝑥1 2𝑥2 2 0.9126 Entry 4 TPT 6 𝑘 = 0.330 + 0.136𝑥1 + 0.068𝑥2 + 0.040𝑥1𝑥2 + 0.010𝑥1 2 + 0.011𝑥2 2 + 0.008𝑥1 2𝑥2 + 0.011𝑥1𝑥2 2 0.9862 𝛼 = 0.572 + 0.073𝑥1 − 0.226𝑥2 − 0.125𝑥1𝑥2 − 0.047𝑥1 2 − 0.044𝑥2 2 + 0.255𝑥1 2𝑥2 + 0.036𝑥1𝑥2 2 0.9567 𝐶𝑝 = 1.740 − 0.297𝑥1 + 0.356𝑥2 − 0.101𝑥1𝑥2 + 0.124𝑥1 2 − 0.006𝑥2 2 + 0.001𝑥1 2𝑥2 + 0.027𝑥1𝑥2 2 + 0.041𝑥1 2𝑥2 2 0.9877 Entry II TPT 30 𝑘 = 0.409 + 0.131𝑥1 + 0.152𝑥2 + 0.007𝑥1𝑥2 − 0.095𝑥1 2 + 0.022𝑥2 2 − 0.097𝑥1 2𝑥2 + 0.007𝑥1𝑥2 2 0.9872 𝛼 = 0.369 + 0.133𝑥1 − 0.164𝑥2 + 0.004𝑥1𝑥2 − 0.049𝑥1 2 + 0.074𝑥2 2 + 0.098𝑥1 2𝑥2 − 0.011𝑥1𝑥2 2 − 0.9880 file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng Oriola et al: Moisture and Temperature Influence on Thermal Properties of Winged Bean (Psophocarpus tetragonolobus) Seed Accessions. AZOJETE, 18(4):707-720. ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 713 0.049𝑥1 2𝑥2 2 𝐶𝑝 = 1.560 − 0.287𝑥1 + 0.168𝑥2 − 0.173𝑥1𝑥2 + 0.321𝑥1 2 + 0.074𝑥2 2 + 0.149𝑥1 2𝑥2 − 0.030𝑥1𝑥2 2 − 0.141𝑥1 2𝑥2 2 0.9886 Entry 12 TPT 32 𝑘 = 0.395 + 0.110𝑥1 + 0.154𝑥2 + 0.014𝑥1𝑥2 − 0.079𝑥1 2 + 0.007𝑥2 2 − 0.078𝑥1 2𝑥2 − 0.006𝑥1𝑥2 2 0.9801 𝛼 = 0.322 + 0.227𝑥1 + 0.054𝑥2 + 0.085𝑥1𝑥2 + 0.101𝑥1 2 + 0.009𝑥2 2 + 0.107𝑥1 2𝑥2 + 0.024𝑥1𝑥2 2 + 0.027𝑥1 2𝑥2 2 0.9959 Where; x1 = Temperature x2 = Moisture content Table 3: Analysis of variance for effect of temperature and moisture content on the specific heat capacities of three winged bean seed accessions 3.2. Thermal conductivity (κ) of three winged bean seed accessions Results of the thermal conductivity of the three winged bean seed accessions at different moisture contents and temperatures are as presented in Table 4. Like the Cp, the κ of the three winged bean seed accessions were observed to increase with an increase in the moisture content irrespective of the samples temperature. But, unlike the Cp, the κ was observed to increase with the temperature for the three seed accessions. The values of thermal conductivities obtained in this study were slightly higher than 0.11 to 0.28 W.m-1K-1 reported for borage seeds (Yang et al., 2002), 0.113 to 0.135 W.m-1K-1 for pumpkin seeds (Kocabiyik et al., 2009), and 0.19 to 0.24 W.m-1K-1 for red lentil seeds (Gharibzahedi et al., 2013). However, it falls within the same ranged of 0.57 to 0.61 W.m-1K-1 for egusi melon (Isa et al., 2014), 0.25 to 0.31 W.m-1K-1 for Bambara groundnut (Abioye et al., 2016), and 0.21 to 0.41 W.m-1K-1 for jack bean seeds (Oriola et al., 2020) within the same moisture contents studied. These values obtained are also within the range of 0.02 to 0.62 W.m-1K-1 for unfrozen food products, as Carson (2017) reported. The high value of the thermal http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):693-706 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 714 conductivity obtained for these winged bean seed accessions indicated better heat conductors. Table 4: Thermal conductivities of three winged bean seed accessions Temperature (oC) Moisture Contents (%) Entry 4 TPT 6 (W/mK) Entry II TPT 30 (W/mK) Entry 12 TPT 32 (W/mK) 5 0.17 ± 0.02g 0.14 ± 0.04h 0.15 ± 0.02i 10 0.18 ± 0.02fg 0.17 ± 0.02gh 0.18 ± 0.05hi 30 15 0.21 ± 0.02fg 0.19 ± 0.04gh 0.21 ± 0.10ghi 20 0.22 ± 0.04efg 0.21 ± 0.04fgh 0.25 ± 0.02fgh 25 0.24 ± 0.03def 0.24 ± 0.02fg 0.27 ± 0.05efg 5 0.28 ± 0.03cde 0.28 ± 0.04f 0.26 ± 0.11efgh 10 0.29 ± 0.05cd 0.36 ± 0.04e 0.33 ± 0.07def 40 15 0.32 ± 0.02c 0.39 ± 0.03de 0.34 ± 0.02de 20 0.39 ± 0.02b 0.46 ± 0.05bcd 0.50 ± 0.04ab 25 0.40 ± 0.02b 0.61 ± 0.06a 0.56 ± 0.07a 5 0.39 ± 0.05b 0.41 ± 0.03de 0.33 ± 0.08def 10 0.42 ± 0.04b 0.42 ± 0.03de 0.38 ± 0.02cd 50 15 0.45 ± 0.04b 0.44 ± 0.02cd 0.44 ± 0.04bc 20 0.58 ± 0.06a 0.51 ± 0.03bc 0.47 ± 0.06b 25 0.60 ± 0.02a 0.52 ± 0.04b 0.51 ± 0.07ab Means within the same column at each temperature with different superscripts are significantly different (p<0.05) Figure 2 represents the surface plot showing the interactions between the temperature, moisture, and the thermal conductivity of the winged bean seed accessions. The thermal conductivity of the winged bean seed accessions increased with moisture contents in a linear (reduced cubic) positive relationship following a second-order polynomial equation. The increase in the thermal conductivity with moisture content in linear relationship obtained in this study agreed with other researchers such as Singh and Goswami (2000) for cumin seed, Yang et al. (2002) for borage seeds, Aviara et al. (2008) for shea nut kernel, Kurozawa et al. (2008) for cashew nut and apple, Kocabiyik et al. (2009) for pumpkin seeds and Gharibzahedi et al. (2013) for red lentil seeds. However, a nonlinear relationship was reported by Oriola (2014) for cassava roots and Oriola et al. (2020) for jack bean seeds. file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng Oriola et al: Moisture and Temperature Influence on Thermal Properties of Winged Bean (Psophocarpus tetragonolobus) Seed Accessions. AZOJETE, 18(4):693-706. ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 715 These differences in the thermal conductivity may be attributed to the variation in seed size, porosity of sample bulk, and seed chemical compositions of each seed accession (for example, oil and protein contents) (Gharibzahedi et al., 2010). Figure 2: Effects of moisture and temperature on thermal conductivities of winged bean seed accessions A polynomial function that best described the effects of temperature and moisture content on the thermal conductivity of the three winged bean accessions was investigated. Second- order polynomial models give the best fit resulting in an R2 value of 0.9862, 0.9872, and 0.9801 was obtained for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32 accessions, respectively (Table 2). This implies that these 2nd order polynomial equations best fit the relationships between temperature, moisture, and the κ of the winged bean seed accessions studied. The model F-values of 71.53, 77.08, and 49.30 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32, respectively (Table 5), implied that the models were significant. The analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the κ of the Entry 4 TPT 6 accession. However, the effects of combined temperature and moisture content were not significant (p > 0.05) with the κ of the Entry II TPT 30 and Entry 12 TPT 32 accessions. Table 5: Analysis of variance for effect of temperature and moisture content on the thermal conductivity of three winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):693-706 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 716 3.3. Thermal diffusivity of three winged bean seed accessions Results of the thermal diffusivity of the three winged bean seed accessions at different moisture contents and temperatures are as presented in Table 6. The Entry 4 TPT 6 accession was observed to have the highest thermal diffusivity values while Entry 12 TPT 32 and Entry II TPT 30 accessions followed, respectively, as the temperature and moisture increased. These values obtained are less than 1.0 and agreed with the thermal diffusivity values published for some other foods in the literature, such as; Cumin seeds by Singh and Goswami (2000), pumpkin seed by Kocabiyik et al. (2009), peanut pod and kernel by Bitra et al. (2010), doum palm fruits by Aremu and Fadele (2010), soybean grains by Pohndorf et al. (2017), and jack bean seeds by Oriola et al. (2020). Table 6: Thermal diffusivities of three winged bean seed accessions Temperatur e (oC) Moisture Contents (%) Entry 4 TPT 6 (m2/s) x 10-7 Entry II TPT 30 (m2/s) x 10-7 Entry 12 TPT 32 (m2/s) x 10-7 5 0.19 ± 0.01c 0.31 ± 0.02def 0.13 ± 0.04g 10 0.41 ± 0.11abc 0.20 ± 0.08fg 0.16 ± 0.06g 30 15 0.45 ± 0.17abc 0.19 ± 0.04fg 0.21 ± 0.02fg 20 0.46 ± 0.16abc 0.19 ± 0.01fg 0.22 ± 0.02fg 25 0.55 ± 0.10abc 0.14 ± 0.01g 0.29 ± 0.02ef 5 0.77 ± 0.07a 0.61 ± 0.04a 0.28 ± 0.05ef 10 0.66 ± 0.12ab 0.46 ± 0.06bc 0.29 ± 0.02ef 40 15 0.53 ± 0.07abc 0.38 ± 0.03cde 0.32 ± 0.03ef 20 0.51 ± 0.17abc 0.30 ± 0.02def 0.36 ± 0.06de 25 0.28 ± 0.09bc 0.28 ± 0.03ef 0.38 ± 0.04de 5 0.68 ± 0.16ab 0.52 ± 0.05ab 0.45 ± 0.03d 10 0.65 ± 0.10ab 0.51 ± 0.05ab 0.58 ± 0.04c 50 15 0.61 ± 0.10ab 0.44 ± 0.03bc 0.62 ± 0.02c 20 0.53 ± 0.14abc 0.42 ± 0.06bcd 0.79 ± 0.04b 25 0.50 ± 0.15abc 0.41 ± 0.05bcd 0.96 ± 0.05a Means within the same column at each temperature with different superscripts are significantly different (p<0.05) Figure 3 represents the surface plot showing the interactions between the three winged bean seed accessions‘ temperature, moisture, and thermal diffusivity. It was observed that the thermal diffusivity of samples of the Entry 4 TPT 6 and Entry 12 TPT 32 generally increased with an increase in moisture content at 30ᵒC while those of Entry II TPT 30 declined with an increase in moisture at the same temperature. Also, at temperatures of 40 and 50ᵒC, the diffusivity of the seed of Entry 4 TPT 6 generally decreased with increased moisture content. The thermal diffusivity of the seeds of the Entry II TPT 30 generally reduced with an increase in moisture content irrespective of the sample temperature. However, seeds of the Entry 12 TPT 32 were observed to increase with both increases in file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng Oriola et al: Moisture and Temperature Influence on Thermal Properties of Winged Bean (Psophocarpus tetragonolobus) Seed Accessions. AZOJETE, 18(4):693-706. ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 717 temperature and moisture. Abioye et al. (2016) reported an increase in the thermal diffusivity with a rise in Bambara groundnut moisture content. In contrast, Adekunle et al. (2013) reported increased in thermal diffusivity with temperature increase for baobab fruit pulp powder. Figure 3: Effects of moisture and temperature dependent on thermal diffusivities of winged bean seed accessions A polynomial function that shows the simultaneously dependent temperature and moisture content on the thermal diffusivities was investigated to correlate experimental data. The best fit resulting in an R2 value of 0.9567, 0.9880, and 0.9959 was obtained for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32 accessions, respectively (Table 2). This implies that these 2nd order polynomial equations obtained could best fit the relationships between temperature, moisture, and the thermal diffusivity of the winged bean seed accessions studied. The model F-values of 22.10, 61.87, and 182.61 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32, respectively (Table 7), implied that the models are significant. The analysis of variance p-values less than 0.05 indicated that the temperature, moisture contents and the combined temperature and moisture content were significant with the thermal diffusivity of the Entry 4 TPT 6 and Entry 12 TPT 32 accessions. However, the effects of combined temperature and moisture content were not significant (p > 0.05) with the thermal diffusivity of the Entry II TPT 30 accession. Table 7: Analysis of variance for effect of temperature and moisture content on the thermal diffusivity of three winged bean seed accessions http://www.azojete.com.ng/ mailto:jbhussein01@mau.edu.ng Arid Zone Journal of Engineering, Technology and Environment, December, 2022; Vol. 18(4):693-706 ISSN 1596-2644; e-ISSN 2545-5818; www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 718 4. Conclusions The influence of moisture and temperature on the thermal properties of winged bean seed accessions revealed that: i. The Cp and thermal conductivity generally increased with increased moisture content for the three winged bean seed accessions. In contrast, the thermal diffusivity decreased with increased moisture content at elevated temperatures (40 and 50 ᵒC). ii. Second-order polynomial models best described the relationship between the studied thermal properties and the temperature and moisture content. The regression equations (R2 ≥ 0.9126, 0.9872, and 0.9801 for Entry 4 TPT 6, Entry II TPT 30, and Entry 12 TPT 32 accessions, respectively) obtained in this study provide a reasonable estimate simulating the thermal properties of the winged bean seeds within the moisture-temperature range studied. iii. The analysis of variance (ANOVA) showed that moisture and temperature have a significant (p < 0.05) effect on the thermal properties of the winged bean seeds. iv. These thermal properties of the winged bean seeds examined will help design considerations for the fabrication of agricultural machines, thermal processes, and equipment needed for storage, drying, heating, and cooling. v. The recommended use of the winged bean seeds' thermal qualities will enable the development of agricultural machinery, thermal systems, and apparatus for heating, cooling, drying, and storing. References Abioye, AO., Adekunle, AA. and Agbasi-Ebere, V. 2016. 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ISSN 1596-2644; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: jbhussein01@mau.edu.ng 719 Adeyanju, JA., Adekunle, AA., Abioye, AO., Ogunlakin, GO., Olajire, AS. and Fashina, OZ. 2019. Determination of moisture-dependent physical and thermal properties of jack bean (Canavalia ensiformis) related to design of processing machines. Nigerian Food Journal, 37(1), 106-116. AOAC. 2010. Official Methods of Analysis of Association of Official Analytical Chemists (18th ed.). Washington D.C Aremu, AK. and Fadele, OK. 2010. Moisture dependence thermal properties of doum palm fruit (Hyphaene thebaica). Journal of Emerging Trends in Engineering and Applied Sciences, 1(2): 199–204. Aviara, NA., Haque, MA. and Ogunjimi, LAO. 2008. Thermal properties of guna seeds. International Agrophysics, 22: 291-297. Bamgboye, AI. and Adejumo, O.I. 2010. Thermal properties of roselle seed. International Agrophysics, 24: 85-87. Bart-Plange, A., Addo, A., Kumi, F. and Piegu, AK. 2012. 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Yang, W., Sokhansanj, S., Tang, J. and Winter, P. 2002. Determination of thermal conductivity, specific heat, and thermal diffusivity of borage seeds. Biosystems Engineering, 82(2):169-176. file:///C:/user/Downloads/azojete143/www.azojete.com.ng mailto:jbhussein01@mau.edu.ng