This study evaluated the effect of the hydrophilic-lipophilic balance (HLB) value gap in mixed surfactants, using polyethylene glycol (PEG)-free surfactants of the polyglyceryl (PG) type, on the emulsification characteristics and stability of MCT Oil-in-Water emulsions. A central composite design (CCD) was conducted, setting the mixed surfactant HLB value (9.5~11.5) and amount of surfactant (2~4 wt%) as independent variables. As a result of optimization, the combination with a large HLB value gap (ES-01) showed an HLB value of 10.37 and a surfactant amount of 3.47 wt%, ESI of 97.7%, MDS of 2.20 mm, and SPAN of 1.00. The combination with a small HLB value gap (ES-02) yielded optimal conditions at a mixed surfactant HLB value of 10.26 and a surfactant amount of 3.59 wt%, ESI of 97.4%, MDS of 3.10 mm, and SPAN of 0.90. Therefore, the combination of surfactants with a small HLB value gap formed a more uniform interfacial arrangement and was more stable than combinations with a large gap. Unlike previous studies that only discussed the influence of the average HLB value of surfactants, this study experimentally demonstrates that the HLB value gap in mixed surfactants directly serves as a design factor for emulsion stability, which is a distinguishing feature of this study.

본 연구는 polyethylene glycol(PEG)-free 계면활성제인 polyglyceryl(PG)계 계면활성제를 이용하여 혼합 계면활성제의 hydrophilic-lipophilic balance(HLB) value gap이 MCT Oil-in-Water 유화액의 유화 특성과 안정성에 미치는 영향을 평가하였다. 혼합 계면활성제 HLB value(9.5~11.5)와 계면활성제의 양(2~4 wt%)을 독립변수로 설정하여 중심합성계획법(central composite design, CCD)을 수행하였다. 최적화 결과, HLB value gap이 큰 조합(ES-01)은 HLB value 10.37, 계면활성제의 양 3.47 wt%에서 ESI 97.7%, MDS 2.20 mm, SPAN 1.00으로 나타났고, HLB value gap이 작은 조합(ES-02)은 혼합 계면활성제 HLB value 10.26, 계면활성제의 양 3.59 wt%에서 ESI 97.4%, MDS 3.10 mm, SPAN 0.90로 최적 조건이 도출되었다. 따라서 HLB value gap이 작은 계면활성제 조합이 큰 조합 대비 더 균일한 계면 배열을 형성하여 안정한 것으로 확인되었다. 이는 기존 연구에서 계면활성제의 평균 HLB value의 영향만 논의된 것과 달리, 혼합 계면활성제의 HLB value gap이 유화 안정성에 직접적인 설계 인자로 작용함을 실험적으로 제시한 점에서 차별성을 갖는다.

Keywords: oil-in-water emulsion, polyglyceryl ester, hydrophilic-lipophilic balance value, emulsion stability, central composite design