The Effect of Sucrose Concentration and Reaction Temperature on the Transparency and Physical Properties of Transparent Solid Soap Based on Virgin Coconut Oil and Secang Wood Extract (Caesalpinia Sappan L.)

Soap is a key cosmetic product for hygiene and bacterial control, and one important innovation is transparent solid soap with a clear, attractive appearance and moisturizing properties. This study investigates the effect of reaction temperature and sucrose concentration on the transparency and physical properties of transparent solid soap formulated from virgin coconut oil (VCO) and secang wood (Caesalpinia sappan L.) extract. VCO was used as the main oil phase due to its stable saturated fatty acids, while secang wood extract was added for its bioactive compounds, including brazilin and flavonoids with antioxidant, anti-inflammatory, and antimicrobial activities. The soap was prepared via saponification of VCO and NaOH with stearic acid, followed by the addition of sucrose solution, citric acid, glycerol, ethanol, and secang wood extract; varying temperatures and sucrose concentrations were applied. Optimal conditions were found at a reaction temperature of 70°C and a sucrose concentration of 70%, yielding soap with good color and transparency, moisture content of 15.2%, pH of 10.33, and foam stability of 89.41%. These properties meet or exceed relevant quality standards and demonstrate that proper control of sucrose level and processing temperature significantly improves the transparency and performance of VCO-based transparent soap enriched with secang wood extract.