Abstract
Soap quality is strongly influenced by the type and fatty acid composition of the lipid used during production. Palm kernel oil and tallow are locally available lipid sources with distinct physicochemical characteristics that may differently affect important soap properties, including foaming, hardness, moisture content, and cleansing performance. However, direct comparison of soaps produced from these two raw materials under similar processing and analytical conditions remains limited. This study evaluated and compared the physicochemical properties of soaps produced from palm kernel oil and tallow using sodium hydroxide as the saponifying agent. The study was carried out to determine the influence of different lipid sources on soap quality and to assess their suitability as locally available raw materials for soap production. Soap samples were prepared separately from palm kernel oil and tallow under controlled conditions using the cold-process method and analysed for pH, moisture content, total fatty matter (TFM), free caustic alkali, foam height, foam stability, hardness, lathering ability, and cleansing efficiency. The results showed that the type of lipid significantly influenced the characteristics of the produced soaps. Palm kernel oil soap exhibited higher foam height (14.52 cm), foam stability (89.74%), lathering ability (9.3), and cleansing efficiency (94.61%) than tallow soap. Conversely, tallow soap showed greater hardness (4.58 kg cm⁻²) and lower moisture content (8.91%), indicating improved durability and reduced dissolution during use. Palm kernel oil soap recorded a pH of 9.68 ± 0.04, foam height of 14.52 ± 0.41 cm, foam stability of 89.74 ± 1.20%, total fatty matter of 79.45 ± 0.52%, lathering score of 9.3 ± 0.2, and cleansing efficiency of 94.61 ± 1.05%. Tallow soap recorded a pH of 9.42 ± 0.05 and showed greater hardness (4.58 ± 0.15 kg cm⁻²) and lower moisture content (8.91 ± 0.28%) than palm kernel oil soap. Both soap samples recorded acceptable pH values and low free caustic alkali content, suggesting effective saponification and suitability for domestic applications. The findings indicate that palm kernel oil is more suitable for producing soaps with strong foaming and cleansing properties, whereas tallow is advantageous for producing harder and longer-lasting soap products. A combination of both raw materials may provide a balanced formulation with improved functional properties.