DETERMINATION OF REQUIRED HLB VALUE 417 In the c ase of CUFO and CUPO, required HLB was tested as 14.9 in this study, but several previous studies reported that required HLB of D-limonene, the main com- ponent in lemon oil, was 12.0 (2,27). However, depending on the geometrical struc- ture of surfactants used in emulsion production, there are cases in which the required HLB for D-limonene was 13.7 (28) and 15.0 (29). In addition, according to Lu et al. (30), the nanoemulsion containing 10% D-limonene showed a minimum particle size and the maximum encapsulation rate when the HLB value was 12, but it is con- sidered that this experiment needs to be expanded beyond HLB 12. The lowe st mean droplet size of HF emulsion (153.97 nm ± 4.23 nm) was obtained at an HLB value of 7.06 (Figure 14). From the turbidity experiment, the CUFO and CUPO emulsions had the minimum droplet size at the highest HLB value of 14.90. Therefore, the CUFO and CUPO needed additional experiments with polysorbate 20 (HLB = 16.70) to have the HLB value higher than 14.90. Figure 5. Appearance after 1 week storage of CJSO emulsions. Figure 6. Turbidity of liquid paraffi n emulsions in the HLB range from 3.70 to 14.90, which were measured by a UV-vis spectrophotometer after 1 week storage at room temperature (n = 3 ±SD).

JOURNAL OF COSMETIC SCIENCE 418 From the additional experiments, the CUFO emulsion had a minimum droplet size (173.73 nm ± 0.43 nm) when HLB = 14.90 in Figure 15A and 127.13 nm ± 95.45 nm for the HLB value of 14.75 in Figure 15B. The CUPO emulsion had a minimum droplet size at an HLB value of 15.35 (126.73 nm ± 0.76 nm) (Figure 15A) and an HLB value of 15.40 (106.27 nm ± 4.89 nm) (Figure 15B). To confi rm wh ether the additional experiments using polysorbate 20 showed the same tendency as the previous experiments, the experiments were conducted using Figure 8. Turbidities of CUFO and CUPO emulsions with (A) surfactant (polysorbate 60: polysorbate 20) HLB range 14.90–16.70, and (B) surfactant (sorbitan sesquioleate: polysorbate 20) HLB range 13.45–16.70, which were measured by a UV-vis spectrophotometer after 1 week storage at room tem- perature (n = 3 ±SD). Figure 7. Turbidities of CUFO, CUPO, HF, and CJSO emulsions in the HLB range from 3.70 to 14.90, which were measured by a UV-vis spectrophotometer after 1 week storage at room temperature (n = 3 ±SD).