Sustainable valorization of animal tallow and Aloe abyssinica gel for bar soap formulation with physicochemical properties and quality assessment

This study investigates the sustainable production of bar soap using locally sourced Aloe abyssinica gel and animal tallow as primary ingredients. Animal tallow was rendered from local butcher waste and characterized, showing a saponification value of 181.78 mg/g NaOH, acid value of 17.32 mg/g NaOH, pH of 5.45, and specific gravity of 0.929 all within acceptable ranges for soap manufacturing. Fresh A. abyssinica gel was extracted from its leaves and characterized by exhibiting 99.23% moisture content, pH of 4.82, refractive index of 1.33, total dissolved solids of 3.350°Brix, and viscosity of 1.359 cP. Twelve soap formulations were prepared using the cold process method, incorporating varying concentrations of A. abyssinica gel (0–25%) with tallow (50–75%), supplemented with coconut oil (15%) and either olive oil or palm oil (10%). Physicochemical analysis revealed that formulations containing 15% A. abyssinica gel demonstrated optimal properties: pH values of 9.75–9.92, total fatty matter content of 73.33–76.8% (Grade I quality), enhanced foamability (4.8–7.3 cm), superior cleansing power, and reduced free caustic alkali (0.08–0.13%). Results confirm that combining A. abyssinica gel with animal tallow produces high-quality, skin-compatible soap while promoting waste valorization and sustainable manufacturing practices.