Deacidification of crude palm kernel oil (CPKO) remains a critical challenge in developing countries, where conventional chemical refining methods are energy-intensive and economically prohibitive for small-scale processors. This study investigated the optimization of CPKO deacidification using kolanut pod ash as an eco-friendly bio-adsorbent through Response Surface Methodology (RSM) with Central Composite Design. Three process variables were evaluated: reaction time (10 - 30 minutes), temperature (60？C - 70？C), and kolanut pod ash dosage (1% - 5% w/w). There was 91% free fatty acid (FFA) content reduction. A significant quadratic model (F-value = 3.82, p = 0.0242) with Adjusted R2 of 0.5718 was obtained. The influential factors were reaction time (p = 0.0111), kolanut pod ash dosage (p < 0.0001), time-temperature (p = 0.0431) and time-dosage (p = 0.0073). Quality parameters remained within acceptable ranges: iodine values (35.4 - 50.3 g I2/100g), acid values (7.18 - 51.02 mg KOH/g), and saponification values (250.67 - 290.12 mg KOH/g). This research demonstrates that kolanut pod ash can serve as an effective, low-cost, and green alternative to synthetic refining agents.
Sundram, K., Sambanthamurthi, R. and Tan, Y.A. (2003) Palm Fruit Chemistry and Nutrition. Asia Pacific Journal of Clinical Nutrition, 12, 355-362.
[3]
St-Onge, M. and Jones, P.J.H. (2002) Physiological Effects of Medium-Chain Triglycerides: Potential Agents in the Prevention of Obesity. TheJournalofNutrition, 132, 329-332. https://doi.org/10.1093/jn/132.3.329
[4]
Poku, K. (2002) Small-Scale Palm Oil Processing in Africa. FAO.
[5]
Japir, A.A., Salimon, J., Derawi, D., Bahadi, M., Al-Shuja’a, S. and Yusop, M.R. (2017) Physicochemical Characteristics of High Free Fatty Acid Crude Palm Oil. OCL, 24, D506. https://doi.org/10.1051/ocl/2017033
[6]
Berger, K.G. (2003) Palm Kernel Oil. In: Encyclopedia of Food Sciences and Nutrition, Elsevier, 4322-4324. https://doi.org/10.1016/b0-12-227055-x/01379-1
[7]
Mba, O.I., Dumont, M. and Ngadi, M. (2015) Palm Oil: Processing, Characterization and Utilization in the Food Industry—A Review. Food Bioscience, 10, 26-41. https://doi.org/10.1016/j.fbio.2015.01.003
[8]
Matth？us, B. (2007) Use of Palm Oil for Frying in Comparison with Other High‐stability Oils. EuropeanJournalofLipidScienceandTechnology, 109, 400-409. https://doi.org/10.1002/ejlt.200600294
[9]
Frega, N., Mozzon, M. and Lercker, G. (1999) Effects of Free Fatty Acids on Oxidative Stability of Vegetable Oil. Journal of the American Oil Chemists’ Society, 76, 325-329. https://doi.org/10.1007/s11746-999-0239-4.
[10]
Gharby, S., Asbbane, A., Nid Ahmed, M., Gagour, J., Hallouch, O., Oubannin, S., etal. (2025) Vegetable Oil Oxidation: Mechanisms, Impacts on Quality, and Approaches to Enhance Shelf Life. FoodChemistry: X, 28, Article 102541. https://doi.org/10.1016/j.fochx.2025.102541
[11]
Dos Santos, C.J., Santos, R.D., Cerqueira, K.S., Rodrigues, J.R.S. and Souza, R.R.D. (2024) Production of Free Fatty Acids by Enzymatic Hydrolysis of Residual Frying Oil Using Non-Commercial Lipases from Aspergillus Niger. AnaisdaAcademiaBrasileiradeCiências, 96, 1-11. https://doi.org/10.1590/0001-3765202420240781
[12]
Sonawane, A. and Waghmode, S. (2023) A Review on Vegetable Oil Refining: Process, Advances and Value Addition to Refining By-Products. In: Environmental Sciences, IntechOpen. https://doi.org/10.5772/intechopen.108752
[13]
Tan, B.A., Nair, A., Zakaria, M.I.S., Low, J.Y.S., Kua, S.F., Koo, K.L., et al. (2023) Free Fatty Acid Formation Points in Palm Oil Processing and the Impact on Oil Quality. Agriculture, 13, Article 957. https://doi.org/10.3390/agriculture13050957
[14]
Gharby, S. (2022) Refining Vegetable Oils: Chemical and Physical Refining. The Scientific World Journal, 2022, 1-10. https://doi.org/10.1155/2022/6627013
[15]
Ortega, J.M., Machado, G.D. and Cabral, V.F. (2026) Recent Advances in Deacidification Techniques for Edible Vegetable Oils: A Comprehensive Review. EuropeanJournalofLipidScienceandTechnology, 128, e70117. https://doi.org/10.1002/ejlt.70117
[16]
Jeevarathinam, G., Rahul, R., Deepa, J., Sharath Kumar, N., Neethu, C.S., Sarojini, G., et al. (2026) Deacidification of Vegetable Oils: Advanced Technologies, Mechanistic Insights, and Emerging Strategies. Food Chemistry, 499, Article 147325. https://doi.org/10.1016/j.foodchem.2025.147325
[17]
Shehu, S., Salleh, M.A. and Ahmad, A.A. (2021) Challenges Facing Palm Oil Industry in Nigeria. Asian People Journal, 4, 26-33. https://doi.org/10.37231/apj.2021.4.1.201
[18]
Gon？alves, J.O., Leones, A.R., de Farias, B.S., da Silva, M.D., Jaeschke, D.P., Fernandes, S.S., et al. (2025) A Comprehensive Review of Agricultural Residue-Derived Bioadsorbents for Emerging Contaminant Removal. Water, 17, Article 2141. https://doi.org/10.3390/w17142141
[19]
Venkatesan, K., Sundarababu, J. and Anandan, S.S. (2024) The Recent Developments of Green and Sustainable Chemistry in Multidimensional Way: Current Trends and Challenges. Green Chemistry Letters and Reviews, 17, 1-12.
[20]
Azimi, A., Azari, A., Rezakazemi, M. and Ansarpour, M. (2017) Removal of Heavy Metals from Industrial Wastewaters: A Review. ChemBioEng Reviews, 4, 37-59. https://doi.org/10.1002/cben.201600010
[21]
Bharathiraja, B., Jayamuthunagai, J., Sudharsanaa, T., Bharghavi, A., Praveenkumar, R., Chakravarthy, M., et al. (2017) Biobutanol—An Impending Biofuel for Future: A Review on Upstream and Downstream Processing Techniques. Renewable and Sustainable Energy Reviews, 68, 788-807. https://doi.org/10.1016/j.rser.2016.10.017
[22]
Karimi, A.M. and Yaghmaei, S. (2016) Biochemical Production of Bioenergy from Agricultural Crops and Residue in Iran. WasteManagement, 52, 375-394. https://doi.org/10.1016/j.wasman.2016.03.025
[23]
Alsulaili, A., Elsayed, K. and Refaie, A. (2024) Utilization of Agriculture Waste Materials as Sustainable Adsorbents for Heavy Metal Removal: A Comprehensive Review. Journal of Engineering Research, 12, 691-703. https://doi.org/10.1016/j.jer.2023.09.018
[24]
Adeoye, A.O., Quadri, R.O., Lawal, O.S. and Emojevu, E.O. (2024) Physicochemical Characterization, Valorization of Lignocellulosic Waste (Kola Nut Seed Shell) via Pyrolysis, and Ultrasonication of Its Crude Bio-Oil for Biofuel Production. Cleaner Waste Systems, 7, Article 100138. https://doi.org/10.1016/j.clwas.2024.100138
[25]
Temitope B, F. (2018) Conversion of Kola Nut Waste into Beneficial Products for Environmental Protection. Journal of Environmental Science and Technology, 11, 233-237. https://doi.org/10.3923/jest.2018.233.237
[26]
Gunst, R.F. (1996) Response Surface Methodology: Process and Product Optimization Using Designed Experiments. Technometrics, 38, 284-286. https://doi.org/10.1080/00401706.1996.10484509
[27]
Anderson, M.J. and Whitcomb, P.J. (2016) RSM Simplified: Optimizing Processes Using Response Surface Methods for Design of Experiments. 2nd Edition, Productivity Press. https://doi.org/10.1201/9781315382326
[28]
Shahzad, H.M.A., Asim, Z., Khan, S.J., Almomani, F., Mahmoud, K.A., Mustafa, M.R.U., et al. (2024) Thermochemical and Biochemical Conversion of Agricultural Waste for Bioenergy Production: An Updated Review. Discover Environment, 2, Article No. 134. https://doi.org/10.1007/s44274-024-00171-w
[29]
Estévez-Sánchez, K.H., Ramos-Morales, M., Ruiz-Espinosa, H., Cortés-Zavaleta, O., García-Alvarado, M.A., Ochoa-Velasco, C.E., et al. (2025) Effect of Particle Size Distribution on Mass Transfer during Solid-Fluid Extraction and Its Application to Coffee Brewing. Journal of Food Engineering, 394, Article 112511. https://doi.org/10.1016/j.jfoodeng.2025.112511
[30]
Box, G.E.P. and Draper, N.R. (2007) Response Surfaces, Mixtures, and Ridge Analyses. 2nd Edition, Wiley.
[31]
Montgomery, D.C. (2017) Design and Analysis of Experiments. 9th Edition, Wiley.
[32]
Payot, T., Chemaly, Z. and Fick, M. (1999) Lactic Acid Production by Bacillus Coagulans—Kinetic Studies and Optimization of Culture Medium for Batch and Continuous Fermentations. EnzymeandMicrobialTechnology, 24, 191-199. https://doi.org/10.1016/s0141-0229(98)00098-2
[33]
Othman, N.H., Latip, R.A., Noor, A.M., Lau, W.J., Goh, P.S. and Ismail, A.F. (2021) Simultaneous Degumming and Deacidification of Crude Palm Oil Using Mixed Matrix PVDF Membrane. IOP Conference Series: Materials Science and Engineering, 1195, Article 012030. https://doi.org/10.1088/1757-899x/1195/1/012030
[34]
AOAC (2010) Official Methods of Analysis of Association of Official Analytical Chemists. 18th Edition, AOAC.
[35]
Wang, Z., Ma, X., Zheng, C., Wang, W. and Liu, C. (2023) Effect of Adsorption Deacidification on the Quality of Peony Seed Oil. Foods, 12, Article 240. https://doi.org/10.3390/foods12020240
[36]
Murphy, O.P., Vashishtha, M., Palanisamy, P. and Kumar, K.V. (2023) A Review on the Adsorption Isotherms and Design Calculations for the Optimization of Adsorbent Mass and Contact Time. ACSOmega, 8, 17407-17430. https://doi.org/10.1021/acsomega.2c08155
[37]
Tsai, Y.H., Chiang, D., Li, Y.T., Perng, T.P., and Lee, S. (2023) Thermal Degradation of Vegetable Oils. Foods, 12, Article 1839. https://doi.org/10.3390/foods12091839
[38]
Okpe, A. (2022) A Comparative Study of Chemical Analysis of Locally Made and Refined Palm Kernel Oil. Science Open Preprints, 2022, 1-40. https://doi.org/10.14293/s2199-1006.1.sor-.pp8vwdq.v1
[39]
Tiefenbacher, K.F. (2017) Technology of Main Ingredients—Sweeteners and Lipids. In: WaferandWaffle, Elsevier, 123-225. https://doi.org/10.1016/b978-0-12-809438-9.00003-x
[40]
Olalere, O.A., Gan, C., Abdurahman, H.N., Ahmad, M.S., Zaid, A.Q. and Habeeb, O.A. (2020) Microstructural and Microchemical Characterization of Valorized Cola Nitida Pod Wastes. ChemicalDataCollections, 26, Article 100356. https://doi.org/10.1016/j.cdc.2020.100356
[41]
Jakobek, L. (2015) Interactions of Polyphenols with Carbohydrates, Lipids and Proteins. FoodChemistry, 175, 556-567. https://doi.org/10.1016/j.foodchem.2014.12.013
[42]
Likozar, B. and Levec, J. (2014) Effect of Process Conditions on Equilibrium, Reaction Kinetics and Mass Transfer for Triglyceride Transesterification to Biodiesel: Experimental and Modeling Based on Fatty Acid Composition. FuelProcessingTechnology, 122, 30-41. https://doi.org/10.1016/j.fuproc.2014.01.017
