Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 355 ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT ORIGINAL RESEARCH ARTICLE THIN LAYER DRYING KINETICS AND INFLUENCE OF DRYING TEMPERATURE ON THE PROXIMATE COMPOSITION OF TIGER-NUT MILK POWDER N. I. Nwagugu1* and W. I. Okonkwo2 1Projects Development Institute (PRODA) Emene Enugu, Nigeria, +2348066733762 2 Agricultural and Bioresources Engineering University of Nigeria Nsukka, Nigeria, *Corresponding author’s email: nnenwagugu@gmail.com ARTICLE INFORMATION ABSTRACT Milk derived from animal sources often contains anti-nutrient elements such as α-lactoglobulin, β-lactoglobulin, lactose and cholesterol, which can contribute to various health challenges. Plant-based milk alternatives, such as tiger-nut milk, offer a healthier option but often face limitations like short shelf life and high storage costs. This study aimed to investigate the drying kinetics and proximate composition of tiger-nut milk powder. Tiger-nut tubers were processed into milk from brown varieties and subsequently dried at 50, 60, and 70°C. Data obtained were fitted to five commonly applied drying mathematical models (Newton, Logarithmic, Page, Henderson and Pabis) to determine the one which predicted the drying kinetics of the milk more accurately. The dried powder was then analyzed for its proximate composition, including moisture content, crude fiber, carbohydrates, protein, lipids, ash, and pH using standardized procedures developed by Association of Official Analytical Chemists (AOAC). The best fit model for the drying kinetics analysis was determined using the coefficient of determination (R²), with the Page model having the highest R² values of 0.998-0.999. This analysis revealed that the Page model accurately describes the drying behavior, with both drying time and equilibrium moisture content decrease as the drying temperature increases. The results also indicated that tiger-nut milk powder contains a moderate protein content (7.12-7.26%), a high carbohydrate content (63.68- 64.17%), and relatively low levels of lipids (6.12-6.24%) and ash (1.42%). These findings suggest that tiger-nut milk powder has the potential to be a valuable plant-based food alternative. Future research should focus on determining its specific mineral composition, bioactive compounds, and potential health benefits. Received: 22nd September 2024 Revised: 2nd April 2025 Accepted: 4th April 2025 Keywords: Milk Drying temperature Drying kinetics Proximate composition Tiger-nut Milk powder Page model © 2025 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved. 1.0 Introduction Milk, an essential food for many people, is produced by mammals like cattle, sheep, goats, and buffalo and provides essential nutrients. Cow milk, which is the most consumed milk worldwide is reported by (Bouglé and Bouhallab, 2017) and (Paul et al., 2020) to provide essential nutrients including proteins (whey and casein protein), fat (palmitic acid, conjugated linoleic acids (CLA), α-linolenic acid (ALA), milk polar lipids (MPL), vitamins (vitamin A, vitamin B complex) and minerals (iron, calcium, magnesium, phosphorus) which have been described to have indispensable functions in the body’s growth (both adults and adolescences), metabolism and maintaining health or well-being. AZOJETE June 2025. Vol.21(2):355-366 Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818 https://doi.org/10.63958/AZOJETE/2025/21/02/004 www.azojete.com.ng http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com mailto:nnenwagugu@gmail.com http://www.azojete.com.ng/ Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 356 Milk is used daily in coffee, breakfast cereals and as an ingredient in cooking and baking (Sebastian and Davis, 2019). Unfortunately, milk from animal sources contain anti-nutrient elements such as α- lacto globulin and ß-lacto globulin which causes food allergies in infants (Ah-Leung et al., 2007), lactose and cholesterol which are associated with some health challenges such as dietary disorders, milk-protein allergy and/or lactose intolerance which have been reported to affect about 70 to 75 % of the human population due to genetically decreased lactase enzyme production (Heine et al., 2017; Sebastian and Davis, 2019) and dietary constraints such as vegan diet and milk allergy (Helsing, 2019; Osthoff et al., 2010). It is also not accessible by the poor owing to its high cost and scarcity. Animal milk consumption is also linked with the increase in low-density lipoprotein as it contains saturated fatty acid and cholesterol (Lordan et al., 2018). Owing to these and other problems associated with milk from animal sources, international organizations such as the WHO (World Health Organization), the FAO (Food and Agriculture Organization of the United Nations), and the IPCC (Intergovernmental Panel on Climate Change) urge a global shift to plant-based diets among which is plant base milk and reported by (2021) to be of high health benefits. Plant-based milk is milk that is extracted from legumes (soya, lupins, peanuts, among others), cereals (oats, rice, spelt, corn, etcetera) pseudo cereal (quinoa, amaranth, teff, etcetera) nuts (almonds, hazelnuts, coconut, macadamia nuts, pistachios) and/or seeds (hemp seeds, flax seeds, sesame seeds, sunflower seeds) (Romulo, 2022), diluted in water, and similar to animal milk in appearance, texture, and use. Such milk has been reported to have different nutritional composition and taste depending on the raw material, method of production, and type of fortification (Sebastian and Davis, 2019). Sebastian and Davis (Sebastian and Davis, 2019) stated that all the nutrients provided by cow’s milk can be obtained from suitable plant-based alternatives. Plant milk can also be obtained from other crops such as lupin, cashew, quinoa, flax, hemp, walnut, hazelnut, and tiger nut. Because of its numerous nutritional and health benefits as well as its ever-increasing market potential, plant-based milk has been referred to as white gold by the Guardian in a report on the unstoppable rise of alternative milk. Among the sources of plant-based milk, tiger nut is one of the commonly available and underutilized ones found in Nigeria (Adebayo-Oyetoro et al., 2019; Ayuba et al., 2020; Ogori et al., 2022). It contains an appreciable amount of healthy nutrients and has so many health benefits. Tiger-nut (Cyperus esculentus L.) is a root tuber that is a member of the family Cyperaceae found in the Eastern Hemisphere, including Southern Europe, Africa, and Madagascar, as well as the Middle East and Indian subcontinent (Adebayo-Oyetoro et al., 2019). It is also known as earth almonds or Zulu nuts (Okudu and Ogubuike, 2016). In Nigeria, it is called Ofio in Yoruba, Aya in Hausa, and Akiaawusa in Igbo (Bamishaiye and Bamishaiye, 2011). Three varieties namely black, brown, and yellow, are easily obtainable in the Country (Bamishaiye and Bamishaiye, 2011). Ayuba et al and Swati et al reported that the nuts help in the prevention and/or treatment of many diseases such as heart attacks, thrombosis, colon cancer and other cancers, obesity, diabetes, and gastrointestinal diseases. Tiger nuts are rich in protein, starch glucose, essential minerals such as phosphorus, potassium, vitamins E and C, fat, and sugar (Gambo and Da’u, 2014). They are also high in fiber, myristic, linolenic, and oleic acid which is heart-friendly and can help to prevent cardiac arrest (Adebayo-Oyetoro et al., 2019; Asante et al., 2014). (Ayuba et al., 2020) found that regular consumption of tiger nuts could reduce the frequency of illness, particularly in sickle cell patients.. The nuts also aid the internal body mechanisms and prevent both constipation and diarrhoea (Adebayo-Oyetoro et al., 2019; Bamishaiye and Bamishaiye, 2011). Tiger-nut is a very useful raw material in such industries as gastronomic, pharmaceutical/medicinal, confectionery, and the biofuel. It is applicable in the manufacture of many useful products including food additives, coffee substitutes, malt caramel, beverages, fermented foods, flour for baking and vegetable oil, and it can be eaten as a snack (Asante et al., 2014; Frank, 2015). A very nutritional beverage called “horchata de chufa” in Spain, “atadwe” in Ghana, and “kunun aya” in Northern Nigeria is produced from Tiger-nut by soaking, milling, sieving and sweetening with flavors and sugar is gaining acceptability. But the Tiger-nut liquid milk has very low shelf life and its storage is energy intensive as the milk has to be stored in a temperature range of 40 to 70 oC making the use of such milk expensive as a result of the increase in the cost of electricity which is the main source of energy for running refrigerators (Paul et al., 2020; Torna et al., 2020). Even in favorable storage conditions, the shelf life http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 357 of such milk is very short as (Abdulfatai et al., 2013) reported that the shelf life of beverage drinks from Tiger-nut tuber is 24 hours. To increase the shelf life of Tiger-nut milk, reduce the cost of storage, and for ease of storage and transportation, the milk needs to be converted into powdered form as reports show that the shelf life of powder milk is far longer than that of liquid milk, and there is no need for refrigeration (Pal et al., 2016). The process of converting liquid milk to powder is through drying which is achieved by reducing the moisture content of the milk to a level that prevents the growth and reproduction of spoilage-causing microorganisms and thus, minimizing many of the moisture-meditated deterioration reactions (Famurewa and Olumofin, 2015). Drying also lead to reduction in the bulkiness of the product thereby minimizing packaging, storage, and transportation costs and enabling storage of the product under ambient temperature to be achieved (Orishagbemi et al., 2000). But the drying process especially under high temperatures, does not only reduce the moisture content of the product but also affects some of its physical, proximate, and chemical compositions as well as its sensory properties. The drying process involves the movement of moisture from the core of the products to the outer surface and then to the surroundings. The rate of moisture removal from produce is dependent on factors such as the initial moisture content of the product, the drying temperature, and the velocity of the drying medium among others. Chukwuma and Ozoma, (2006) reported that the characteristics and behaviour of the drying material can be described and represented using mathematical models. These models are used in designing and analysing drying systems (Famurewa and Olumofin, 2015). Several drying models such as Empirical Models among which include (page, Henderson and Pabis, Newton, Logarithmic and Two-term Models among others) (Akpinar, 2006), Semi-Empirical Models (modify page and Midilli Models) (Bryś et al., 2021) and Theoretical Models (Diffusion-Based Models, Capillary Theory and Film Theory) (Erbay and Icier, 2010) were developed by many researchers which are suitable to explain the drying behaviours of different products. Therefore, this study is aimed at studying the drying kinetics of Tiger nut milk in a thin layer dryer, and investigating the effect of drying temperature on the proximate composition of milk powder. The study will therefore, provide the appropriate drying temperature for drying Tiger-nut milk to powder as well as the best-fit Empirical drying model for the drying process. 2. Materials and Methods 2.1 Materials Used The Materials used in this study include: Brown Tiger-nut, Weighing Balance (aeAdam model number AE7681116, 2000g ×0.01g), Blender (EuroSonic Model Number: ES-910, Capacity: 1.8 Litres), Digital thermometer (Custom model number: CT-220 measuring range: -50 to +200 oC, Resolution: 0.1 oC), Modular Cold Room (Riva Cold, Model: MCR1, Temperature Range -50C to 5 oC), Drying Pan ( Aluminum tray 25 by 40 cm by 3 cm deep), Hot Air Electric Oven (Genlab, Model OV/200/F/DIG- R38, 2 kW, temperature Range: 30 to 250 oC). 2.2 Sample Preparation Brown Tiger-nut (Cyperus esculent) was procured from a Tiger-nut whole seller in the central market Bauchi metropolis, Bauchi State. The Tiger nuts were then sieved using a 12 mm sieve to remove sand, impurities, and other materials and then washed several times with clean water, sun dried, and stored in air-tight polythene bags for use in producing the milk. The initial moisture content of the Tiger nut was determined to be 32.4% wet basis using oven drying method at 105 0C. 2.3 Milk Extraction and Drying The Tiger-nut milk was extracted following the procedure described by (Romulo, 2022) with some modifications. From the clean dried Tiger-nut, 450 g were soaked in twice its volume of water at 40 oC for 12 hours placed inside Genlab Hot Air oven (Model OV/200/F/DIG-R38) to maintain the temperature. The sample was then drained and washed in clean water. The moisture content of the sample was then determined using oven drying method at 105 0C to be 38.7%. The soaked Tiger-nut was then ground using the kitchen blender (EuroSonic Model Number: ES-910) at high speed of 9,645 rpm for 5 minutes and filtered through cheesecloth to obtain Tiger-nut milk. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 358 The quantity of water used in grinding the Tiger-nut and filtering the milk was twice the volume of the Tiger-nut after soaking. The liquid Tiger-nut milk was then pasteurized in a non-stick pan at 72 oC for 15 sec and stored in a refrigerator at 4 oC for 24 hrs before drying. The liquid milk was dried in a hot air oven (Genlab, Model OV/200/F/DIG-R38) using shallow drying trays at three different temperatures: 50, 60, and 70 oC. The milk samples were weighed hourly to determine weight loss following the method described by (Abano et al., 2021), which was used to study drying kinetics and drying time. The drying process continued until the milk was completely dry, as indicated by three consecutive weighs showing no change in weight. At the end of the drying process, the equilibrium moisture content (me) was determined using oven drying method at 105 0C for 24 hours. The dried milk was then blended to powder using a blender and stored for proximate analysis. The whole process of milk production and drying was replicated 3 times to reduce error in the results. 2.4 Drying Kinetics of the Tiger Nut Milk Data obtained from the drying tests as described in section 2.3 were used in analyzing the drying kinetics of the Tiger-nut milk powder thus: 2.4.1 Drying rate The rate of drying of the Tiger-nut milk was determined using the Equation 1 (Abano et al., 2021) DR = 𝑀𝑡+∆𝑡−𝑀𝑡 ∆t 1 where: DR is drying rate, g H2O/min, 𝑀𝑡+∆𝑡 𝑎𝑛𝑑 𝑀𝑡 are moisture contents, g H2O /g of dry solid at drying time t, ∆t is drying time, min The original moisture content of the milk, the moisture content during the drying process and the equilibrium moisture content were determined using Equation 2 and the data obtained were used to determine the moisture ratio. 𝑀𝑡 = 𝑊0−𝑊1 𝑊1 2 where: 𝑀𝑡 is Product moisture content at a specified time during the drying operation, g of water, 𝑊0 is the weight of the sample before drying, g, 𝑊1 is the weight of after dry, g The moisture ratio was calculated using Fick's diffusion equation (Equation 3), as presented by Eunice (Eunice, 2018). The equilibrium moisture content was achieved by continuous monitoring of weight change until no further changes occured. The calculated moisture ratios were then plotted against drying time to create a drying curve, from which regression equations for the drying of tiger-nut milk were developed 𝑀𝑅 = 𝑀𝑡−𝑀𝑒 𝑀𝑜−𝑀𝑒 3 where: 𝑀𝑡 is moisture content at time t, % dwb, 𝑀𝑒 is equilibrium moisture content, % dwb, 𝑀𝑜 is initial moisture content, % dwb. 2.4.2 Mathematical modeling of the drying process The data obtained from the computation of moisture ration 𝑀𝑅 at different drying periods were used to develop an empirical model based on the assumption that resistance to water movement to the surface of the sample was negligible and that the resistance to water evaporation was concentrated on the surface of the sample (Abano et al., 2021). This phenomenon is similar to Newton’s law of cooling. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 359 Five empirical drying models applicable to thin layer drying shown in the Equations 4 to 8 (Table 1) were used to study the drying behaviour of the Tiger-nut milk. The drying rate constant 𝑘, 𝑘𝑜 and 𝑘1 and drying coefficients a, b, 𝑐 and 𝑛 were determined using a nonlinear regression procedure on SPSS version 25 following the procedure described by Rasmussen et al 2021 and Yi et al, 2012 The goodness of the fit of each drying models was assessed using the coefficient of determination (R2) as shown in Equation 9 and the model with the highest R2 was selected to best describe the drying of the Tiger- nut milk. Table 1: Mathematical models fitted to the drying data Model Name Equation Reference Newton 𝑀𝑅 = exp(−𝑘𝑡) … 4 (Jahanbakhshi et al., 2020) Logarithmic 𝑀𝑅 = a exp(−𝑘𝑡) + 𝑐 … 5 (Coşkuner et al., 2002) Page 𝑀𝑅 = exp(−𝑘𝑡𝑛) … 6 (Eunice, 2018) Handerson and Pabis 𝑀𝑅 = aexp(−𝑘𝑡) … 7 (Aviara and Igbeka, 2016) Two term 𝑀𝑅 = aexp(−𝑘𝑜𝑡) + bexp(−𝑘1𝑡) … 8 (Famurewa and Olumofin, 2015) Where: 𝑡 is time (min), 𝑘, 𝑘𝑜 and 𝑘1 are drying rate constant (min-1) and a, 𝑐 and 𝑛 are drying coefficients. 𝑅2 = 1 − ∑(𝑀𝑅𝑝𝑟𝑒−𝑀𝑅𝑎𝑐𝑡) 2 ∑(𝑀𝑅𝑎𝑐𝑡−𝑀𝑅𝑎𝑐𝑡.𝑎𝑣𝑔) 2 9 Where: 𝑅2 is coefficient of determination, 𝑀𝑅𝑝𝑟𝑒 is predicted moisture ratio, 𝑀𝑅𝑎𝑐𝑡 is Experimental moisture ratio, 𝑀𝑅𝑎𝑐𝑡.𝑎𝑣𝑔 is the Average experimental moisture ratio 2.5 Validation of the Model To validate the predictive accuracy of the selected models, the predicted moisture ratios were plotted against the experimental drying time for each of the three drying temperatures. Additionally, a plot of predicted moisture ratio against observed moisture ratio was created, and the R² value of the linear trend line fitted to this plot was evaluated. A closer R² value to 1 indicates a better fit between the predicted and observed data. 2.6 Proximate Analysis The proximate composition of the dried Tiger-nut milk was determined using standard methods as follows: Crude protein content, mineral ash content, and crude fiber content were determined following the procedure given by the Association of Official Analytical Chemists (AOAC) (2000), crude fat content was determined using the Soxhlet method as reported by (Ndubuisi, 2009). Carbohydrate content of the milk was obtained by difference as reported by (Frank, 2015). The carbohydrate content was calculated by subtracting the sum of the protein, fat (lipid), fiber, and ash from the total dry matter. While the energy value of the milk was calculated by multiplying the mean values of the crude protein, fat, and carbohydrates by the At water factors of 4, 9 and 4 respectively (FAO, 2006) as reported by (Frank, 2015) and represented in Equation 10. The obtained energy values were converted to kilo- joule (KJ) using a conversion factor of 4.184 (approximately 4.2) to multiply the energy values given in Kcal (Ndubuisi, 2009). Energy Value = (4 × protien + 9 × fat + 4 × carbohydrate) ∗ 4.184 10 2.7 Statistical Analysis All the experiments were carried out in replications. The drying data and proximate analysis results were subjected to Analysis of variance (ANOVA) using SPSS version 23 to investigate the effect of drying temperature on the drying time and the various proximate composition of the milk. 3. Results and Discussions The effects of drying temperature on the drying kinetics and proximate composition of tiger-nut milk powder were investigated. The results are presented below: http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 360 3.1 Drying Kinetics Table 2 presents the results of modeling the drying behavior of tiger-nut milk at varying temperatures (50, 60, and 70°C) using five drying models: Newton, Logarithmic, Page, Henderson and Pabis, and Two-term. The table includes drying rate constants (k, k'), drying coefficients (a, b, c, n), and coefficient of determination (R²) values for thin-layer drying. All five models demonstrated a good fit for describing the thin-layer drying of tiger-nut milk, aligning with the findings of (Famurewa and Olumofin, 2015). A model with an R² value greater than 0.9 is generally considered to accurately represent the drying characteristics of a product. The R² values for all models in this study ranged from 0.936 to 0.999. The Newton model exhibited the least fit, with R² values between 0.936 and 0.945 for all three temperatures. The Henderson and Pabis model followed with R² values ranging from 0.857 to 0.962. The Page model demonstrated the best fit for all three temperatures, with R² values of 0.998 to 0.999. Figure 1 illustrates the relationship between moisture ratio and drying time for both experimental data and the Page model at 50, 60, and 70°C. The plots indicate that moisture reduction begins after the first hour of drying for all three temperatures, suggesting a falling rate period. Drying at 50°C required 22 hours to complete, likely due to the lower energy of water molecules at lower temperatures. In contrast, drying at 60 and 70°C took 20 and 15 hours, respectively, as the higher temperatures increased the energy of the water molecules. The equilibrium moisture contents of the milk were determined to be 8.23%, 6.95%, and 5.78% for drying at 50, 60, and 70°C, respectively. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 361 Table 2: Fitting of Thin Layer Drying of Tiger-nut Milk to Three Selected Drying Models Drying Temperature 0C Newton Model Logarithmic Model Page Model Handerson and Pabis Two-term k R2 A k C R2 K N R2 a k R2 a 𝑘𝑜 b 𝑘1 R2 50 0.115 0.936 1.394 0.077 -0.309 0.986 0.024 1.689 0.998 1.147 0.131 0.957 0.831 0.131 0.316 0.131 0.957 60 0.156 0.945 1.254 0.126 -0.158 0.982 0.040 1.679 0.999 1.141 0.175 0 .962 30.563 0.080 -29.469 0.077 0.984 70 0.124 0.938 1.288 0.153 -0.190 0.980 0.052 1.756 0.999 1.142 0.223 0.957 34.791 0 .096 -33.693 0.094 0 .982 k, 𝑘𝑜 and 𝑘1 are drying rate constants, a, b, c, and n are model constants and R2 is the Coefficient of determination. Figure 1: Experimental and Page Model Drying Curves for Tiger-nut milk dried at 50, 60 and 70 0C. -0.2 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 20 25 30 M o is tu re R at io Drying Time (hr) Exp @50 deg page @ 50 deg Exp @ 60 deg page @ 60 deg Exp @ 70 deg Page @ 70 Deg http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 362 3.2 Proximate Composition Results The analysis of variance (ANOVA) for the effect of drying temperature on the proximate composition of the tiger-nut milk power is presented in Table 3. The ANOVA indicates that drying temperature significantly influences all the determined proximate components. Among the proximate compositions, carbohydrate content was most affected by temperature, as evidenced by the highest F-value of 61600.522. Other proximate components significantly impacted by temperature included crude fibre (F-value = 29606.173), pH (F-value = 9408.129), energy (kcal) (F-value = 7192.206), moisture content (F-value = 3433.836), energy (kJ) (F-value = 2403.589), lipid content (F-value = 1444.895), ash content (F-value = 688.345), and crude protein content (F- value = 620.794). Table 3: ANOVA for the effect of Temperature on the Proximate Composition of Tiger-nut Milk Powder Source Dependent Variable Type III Sum of Squares df Mean Square F Sig. Drying Temperature (0C) Moisture Contain (%) 200.765 3 66.922 3433.836 <0.001 Ash (%) 18.379 3 6.126 688.345 <0.001 Crude Protein (%) 445.937 3 148.646 620.794 <0.001 Lipid (%) 343.500 3 114.500 1444.895 <0.001 Crude Fiber (%) 1382.608 3 460.869 29606.173 <0.001 pH 159.938 3 53.313 9408.129 <0.001 Carbohydrate (%) 36617.404 3 12205.801 61600.522 <0.001 Energy (kcal) 1038790.258 3 346263.419 7192.206 <0.001 Energy (kj) 17949558.582 3 5983186.194 2403.589 <0.001 Table 4 presents the mean proximate composition per 100 g of Tiger-nut milk powder for milk dried at 50, 60, and 70 oC with their respective standard deviations in parenthesis. The results indicated that drying temperature influences all the proximate elements. Table 4: Proximate Composition of Tiger-nut Milk Powder per 100 g Dried at Various Temperatures Drying Temperature (0C) Moisture Contain (%) Ash (%) Crude Protein (%) Lipid (%) Crude Fiber (%) pH Carbohydrate (%) Energy (kcal) Energy (kJ) 50 4.84 (0.15) 1.43 (0.1) 7.12 (0.3) 6.12 (0.29) 12.42 (0.11) 4.21 (0.06) 64.17 (.062) 340.24 (4.97) 1423.56 (29.08) 60 4.81 (0.18) 1.41 (0.09) 7.22 (0.65) 6.18 (0.33) 12.39 (0.15) 4.23 (0.08) 63.76 (0.3) 339.54 (8.05) 1420.64 (56.68) 70 4.51 (0.07) 1.42 (0.1) 7.26 (0.46) 6.24 (0.2) 12.36 (0.11) 4.2 (0.09) 63.68 (0.34) 339.92 (7.42) 1422.23 58.39) Values in the parenthesis are standard deviations of three replications The moisture content of the Tiger-nut milk powder dried at 50 oC was 4.84% and is slightly higher than that of the milk dried at 60 and 70 oC which was of 4.81 and 4.51%, respectively. The moisture content range (4.84 to 4.51%) of the Tiger-nut powder milk was close to 4.15 ± 0.03 % obtained by Aidoo et al. (2010) for skimmed milk powder, 4.32 % and 4.89 % for Soymilk powder and Okara (soy pulp), respectively, reported by Osthoff et al. (2010). The moisture content of the Tiger-nut milk powder was found to fall within the safe and ideal storage moisture content of powder milk reported by Osthoff et al. (2010) and recommended by Codex Alimentarius (Marie et al., 2004). The crude fiber content of the Tiger-nut milk powder was found also to be inversely affected by drying temperature to a lesser extent as the highest crude fiber content of 12.42% was found in milk dried at 50 oC which decreased to 12.39% for the milk dried at 60 oC while the least crude fiber content of 12.36% was obtained for milk dried at 70 oC. The fiber content of the Tiger-nut milk was found to be higher than 0.26%, and 2.58% found for skimmed milk powder, and dehydrated peanut-cowpea milk reported by Aidoo et al. (2010). The Tiger-nut powder milk was found to have an average carbohydrate content of 63.76% for milk dried at 60 oC with a minimum and maximum values of 63.68% for milk dried at 70 oC and 64.17% for milk dried at 50 http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. ISSN 1596-2490; e-ISSN2545-5818; www.azojete.com.ng Corresponding author’s email address: nnenwagugu@gmail.com 363 oC, respectively. Indicating that the milk contains large amount of energy. Closer carbohydrate content of 65.10% is reported for tiger-nut microencapsulation powder milk by Neto et al. (2019) but a far lower value of 2.21 and 10.73 % were reported by Ogori et al. (2022) and Abdulfatai et al. (2013) respectively for Tiger- nut milk. Protein is a vital component for living organisms, regulating body metabolism and serving as a storage form of carbon and nitrogen (Famurewa and Olumofin, 2015). The crude protein content of the tiger-nut milk powder in this study ranged from 7.12 to 7.26%. Drying temperature was found to influence protein content, with lower temperatures resulting in lower protein levels and higher temperatures yielding higher protein content. This finding suggests that drying conditions can be optimized to maximize protein retention in the final product. The protein content of the tiger-nut milk powder was comparable to the 7.69% reported by Frank (2015) for a similar product. However, it was lower than the 11-15% range for oat milk (Swati et al., 2016) and significantly lower than the 37.81% and 29.90% reported for soymilk powder and okara milk, respectively Osthoff et al. (2010). Additionally, the protein content was higher than the 4.43% reported for almond milk powder (Bueno, 2018) and exceeded the minimum recommended level of 2.2% for plant-based milk according to Drewnowski et al. (2021). While tiger-nut milk powder may not be as protein-rich as some other plant-based milk alternatives, its moderate protein content can contribute to a balanced diet. The influence of drying temperature on protein content provides opportunities for optimizing production processes to enhance the nutritional value of tiger-nut milk powder. The lipid content of tiger-nut milk was found to increase with an increase in drying temperature as the least lipid content of 6.12% was found in the milk dried at 50 oC followed by 6.18% in milk dried at 60 oC with the highest lipid content of 6.24% found in the milk dried at 70 oC. The lipid content of the tiger-nut powder milk was found to be lower than 23.70% obtained by Neto et al. (2019) for tiger-nut milk produced by microencapsulation process and 22.44% for soymilk powder obtained by Osthoff et al. (2010) but is within the range of 9.01% for okara milk obtained by Osthoff et al. (2010) and 5–9 % for oat milk reported by Swati et al. (2016). Tiger-nut milk powder offers a relatively low-lipid content compared to some other plant-based milk alternatives, making it a suitable option for individuals seeking to reduce their dietary fat intake The Ash content of the milk was found to remain around 1.42% which is below 3.16% for okara milk powder, 6.53, 7.5 and 8.11 % for soymilk powder, high milk protein powder and skimmed milk powder respectively reported by Osthoff et al. (2010), Marie et al. (2004) and Aidoo et al. (2010), respectively. The ash content of the tiger-nut milk powder was found to be within the same range as 2.43% obtained by Frank (2015) for tiger- nut milk powder and close to that of cow milk powder (5.72 %) reported by El- Sara (2009). The pH of the milk was found to be around the acidic range of 4.21 which is below 6.68 for soymilk powder (Osthoff et al., 2010), 6.73 for tiger-nut milk (Abdulfatai et al., 2013) and 6.70 to 7.03 for reconstituted tiger-nut milk (Neto et al., 2019). The pH of the tiger-nut milk was also lower than those of goat milk 6.80, cow milk 6.80 and camel milk 6.25 (El- Sara, 2009) but is higher than those of most fruit juices such as apple juice (3.61) and pineapple juice (3.67) (Abdulfatai et al., 2013). Generally, the acidic nature of the milk may aid in digestion. Some studies suggest that acidic beverages can contribute to digestive processes (Wang et al., 2017). The energy content of the milk calculated using the At water factors remained around 339.92 kcal (1422.23 kJ) per 100 g of the milk as the drying temperature increased. This energy is above 170–200 kcal minimum energy recommended by (Drewnowski et al., 2021) for plant-based milk indicating that the milk has high energy content. 4. Conclusion This study investigated the proximate composition and drying behaviour of tiger-nut milk powder, a promising plant-based milk alternative. Key findings include a balanced nutritional profile with a moderate protein content (7.12-7.26%), high carbohydrate content (63.68-64.17%), and relatively low lipid (6.12-6.24%) and ash (1.42%) levels. The Page model accurately represents the drying kinetics of tiger-nut milk powder, while drying time and equilibrium moisture content decreased with increasing temperature. These findings suggest that drying conditions can be optimized to improve the quality and efficiency of tiger-nut milk powder production. Tiger- nut milk powder offers a valuable addition to the plant-based food market. Its unique nutritional composition and potential health benefits warrant further research to explore specific mineral content, bioactive compounds, and their implications for consumer health. http://www.azojete.com.ng/ mailto:nnenwagugu@gmail.com Arid Zone Journal of Engineering, Technology and Environment, June 2025; Vol. 21(2): 355-366. 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