• 한국응용과학기술학회지
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• 제26권4호
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• pp.407-414
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• 2009

Water-in-Oil (W/O) emulsions are widely used in cosmetics. However, O/W (Oil-in-Water) emulsions are generally superior to W/O emulsions in terms of stability. In this study, we investigated the changes of viscosity, the size of emulsion droplets, and rheological properties of emulsions prepared using distearyldimonium chloride (DDC), magnesium aluminum silicate (MAS) and quaternium-18 hectorite (QH). In addition to the changes of the composition, we tested the condition of homogenization including rotation per minute of the mixer and the mixing time. The viscosity of emulsions with DDC and AMS were not changed with time and the stability of emulsions was stable during the storage time. However, the fluidity of emulsions were low due to the forming gel network in the emulsions. The gelling power of the emulsions with QH was rather weaker than that of the emulsions with DDC and MAS. The viscosity of emulsions with QH was gradually reduced and the phase separation of emulsions with high concentration of oil was observed throughout the storage time, however, the stability of emulsions with DDC, MAS and QH was excellent, the fluidity of emulsions was enhanced, and the viscosity of emulsions was sustained for a long time after setting of emulsions.

• Food Science and Biotechnology
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• 제18권2호
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• pp.299-306
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• 2009

The purpose of this study was to prepare stable water-in-corn oil (W/O) emulsion droplets coated by polyglycerol polyricinoleate (PGPR). W/O emulsions (20 wt% aqueous phase, 80 wt% oil phase containing 8 wt% PGPR) were produced by high pressure homogenization (Emulsions 1), however, appreciable amount of relatively large water droplets (d>$10{\mu}m$) were found. To facilitate droplet disruption, viscosity of each phase was adjusted: (i) increased the viscosity of aqueous phase by adding 0.1 wt% xanthan (Emulsions 2); (ii) decreased the viscosity of oil phase and aqueous phase by heating them separately at $50^{\circ}C$ for 1 hr immediately before emulsification (Emulsions 3). Homogenizing at the elevated temperature clearly led to a smaller water droplet size, whereas xanthan neither improved nor adversely affected on the microstructures of the emulsions. In addition, the Emulsions 3 had good stability to droplet aggregation under shearing stress, thermal processing, and long term storage.

• 대한화장품학회지
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• 제36권1호
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• pp.1-16
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• 2010

본 총설에서는 나노미터 크기의 고체 입자가 오일-물 계면에 흡착됨으로써 안정화된 에멀젼의 제조와 성질에 대하여 기술하였다. 이렇게 제조된 에멀젼을 Pickering 에멀젼이라 하며 이 에멀젼을 계면활성제로 안정화된 일반적인 에멀젼과 비교하였다. Pickering 에멀젼의 독특한 성질은 입자의 계면 흡착 에너지가 큰 점에 기인하며 일반 에멀젼과 주요한 차이점은 고체 입자가 비가역적으로 계면에 흡착한다는 사실이다. Pickering 에멀젼의 전상은 w/o (water-in-oil) 타입에서 o/w (oil-in-water)로 수상의 분율이 증가함에 따라 발생한다. 친수성의 입자는 o/w 에멀젼을 형성하는 경향을 보이고 친유성 입자는 w/o 에멀젼을 형성하는 경향을 보이며 이는 고체 입자의 오일-물 계면에서의 접촉각에 따른다. Pickering 에멀젼의 안정성은 많은 부분에서 일반적인 에멀젼과는 다른 거동을 보였다. 저자는 또한 Pickering 에멀젼의 화장품 응용 가능성에 대해서도 논의하였다.

• Korea-Australia Rheology Journal
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• 제15권3호
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• pp.125-130
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• 2003

The emulsion stability of cosmetic creams based on the water-in-oil (W/O) high internal phase emulsions (HIPEs) containing water, squalane oil and cetyl dimethicone copolyol was investigated with various compositional changes, such as electrolyte concentration, oil polarity and water phase volume fraction. The rheological consistency was mainly destroyed by the coalescence of the deformed water droplets. The slope change of complex modulus versus water phase volume fraction monitored in the linear viscoelastic region could be explained with the resistance to coalescence of the deformed interfacial film of water droplets in concentrated W/O emulsions: the greater the increase of complex modulus was, the more the coalescence occurred and the less consistent the emulsions were. Emulsion stability was dependent on the addition of electrolyte to the water phase. Increasing the electrolyte concentration increased the refractive index of the water phase, and thus decreased the refractive index difference between oil and water phases. This decreased the attractive force between water droplets, which resulted in reducing the coalescence of droplets and increasing the stability of emulsions. Increasing the oil polarity tended to increase emulsion consistency, but did not show clear difference in cream hardness among the emulsions.

• Food Science and Biotechnology
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• 제16권6호
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• pp.999-1005
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• 2007

An oil-in-water (O/W) emulsion [20 wt% com oil, 0.5-6.0 wt% fish gelatin (FG), pH 3.0] was produced by high pressure homogenization, and the influence of pH, protein concentration, and homogenization condition on the formation of FG-stabilized emulsions was assessed by measuring particle size distribution, electrical charge, creaming stability, microstructure, and free FG concentration in the emulsions. Optical microscopy indicated that there were some large droplets ($d>10\;{\mu}m$) in all FG-emulsions, nevertheless, the amount of large droplets tended to decrease with increasing FG concentration. More than 90% of FG was present free in the continuous phase of the emulsions. To facilitate droplet disruption and prevent droplet coalescence within the homogenizer, homogenization time was adjusted in O/W emulsions stabilized by 2.0 or 4.0 wt% FG. However, the increase in the number of pass rather promoted droplet coalescence. This study has shown that the FG may have some limited use as a protein emulsifier in O/W emulsions.

• 한국가시화정보학회지
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• 제20권3호
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• pp.10-18
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• 2022

We present an experimental investigation on emulsions created during the impact process between a surfactant-laden droplet and an oil layer on water. By varying the surfactant concentration and the viscosity of oil layer, we created emulsions and visualized them using multi-dimensional high-speed imaging. Our analysis shows that the emulsions are more likely to be unstable and decay within a minute if the impacting droplet contains more surfactant. We also found that there are three mechanisms of generation of emulsions depending on the concentration of surfactant and the viscosity of oil layer; the jet pinch-off, cavity pinch-off, and tearing of oil layer. Jet and cavity pinch-off turned out to be dominant mechanisms for high oil viscosities, while tearing of oil layer is dominant for low oil viscosities. Our result is potentially useful in designing optimal dispersant properties for offshore oil contamination.

• Food Science and Biotechnology
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• 제18권3호
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• pp.610-617
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• 2009

The stability of corn oil-in-water emulsions coated by milk proteins, sodium caseinate (CAS), or whey protein concentrate (WPC), was compared under the environmental stress of pH change. Emulsions were prepared at 0.1 of protein:oil because the majority of droplets were relatively small ($d_{32}=0.34$ and $0.35\;{\mu}m$, $d_{43}=0.65$ and $0.37\;{\mu}m$ for CAS- and WPC-emulsions, respectively) and there was no evidence of depletion flocculation. As the pH of the emulsions was gradually dropped from 7 to 3, there was no significant difference in the electrical charges of the emulsion droplets between the 2 types of emulsions. However, laser diffraction measurements, microscopy measurements, and creaming stability test indicated that WPC-emulsions were more stable to droplet aggregation than CAS-emulsions under the same circumstance of pH change. It implies that factors other than electrostatic repulsion should contribute to the different magnitude of response to pH change.

• Food Science and Biotechnology
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• 제17권1호
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• pp.8-14
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• 2008

The influence of salt concentration on the stability of sodium caseinate (CAS)-stabilized emulsions (20 wt% corn oil, 3.2 wt% CAS, 5 mM imidazole/acetate buffer, pH 7) was examined. In the absence of salt, laser diffraction measurements and optical microscopy measurements indicated there were some large oil droplets ($d>10\;{\mu}m$) in the emulsions stabilized by 0.8 to 3.2 wt% of CAS. The droplet aggregation (mostly droplet coalescence) observed in the emulsions containing ${\leq}2.8\;wt%$ CAS tended to decrease as the CAS concentration increased, however, after which concentration (at 3.2 wt% CAS) depletion flocculation occurred. The addition of $CaCl_2$ (5-20 mM) into the emulsions stabilized by 3.2 wt% CAS prevented the depletion flocculation although there was a small fraction of relatively large individual droplets in the emulsions, which was attributed to electrostatic screening effect and bridging effect of calcium ion. This study has shown that calcium ion that has been reputed to promote droplet aggregation could improve emulsion stability against droplet aggregation in CAS-stabilized emulsions.

• 한국식품영양과학회지
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• 제19권6호
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• pp.612-616
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• 1990

전상이 일어나기 직전의 W/O형 에멀젼에는 W/O형 에멀젼과 섞여 O/W/O 형 에멀젼이 생성한다는 것을 알았다. 그래서 W/O형 에멀젼 중에 분산된 O/W/O형 분산의 정도를 평가하기 위한 목적으로 시료 에멀젼(수상 :물, 유상 TGCR을 함유한 올리브유)을 원추 평판형 회전 점도계를 사용하여 전단속도 1.92-384sec$^{-1}$(온도 25$\pm$0.1$^{\circ}C$)에서 점도를 측정하고 이 값을 Mooney의 점도식에 대입하여 이론치와 실측치의 차로부터 O/W/O형 분산의 정도를 평가했다. O/W/O형 에멀젼의 생성은 전상 직전의 시료에서 높았고, 유화제인 TGCR의 농도가 낮을수록 O/W/O형 에멀젼의 생성이 증가되는 경향이 나타났다. 이러한 사실로부터 W/O형 에멀젼이 전상 직전 부근에서 이론적으로 설명할 수 없는 고점도 현상이 전상직전의 O/W/O형 에멀젼의 생성에 의해서도 일어날 가능성이 있다고 사료된다.

• Korea-Australia Rheology Journal
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• 제18권4호
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• pp.183-189
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• 2006

High internal phase emulsions are highly concentrated emulsion systems consisting of a large volume of dispersed phase above 0.74. The rheological properties of high internal phase water-in-oil emulsions were measured conducting steady shear, oscillatory shear and creep/recovery experiments. It was found that the yield stress is inversely proportional to the drop size with the exponent of values between 1 and 2. Since the oil phase contains monomeric species, microcellular foams can easily be prepared from high internal phase emulsions. In this study, the microcellular foams combining a couple of thickeners into the conventional formulation of styrene and water system were investigated to understand the effect of viscosity ratio on cell size. Cell size variation on thickener concentration could be explained by a dimensional analysis between the capillary number and the viscosity ratio. Compression properties of foam are important end use properties in many practical applications. Crush strength and Young's modulus of microcellular foams polymerized from high internal phase emulsions were measured and compared from compression tests. Of the foams tested in this study, the foam prepared from the organoclay having reactive group as an oil phase thickener showed outstanding compression properties.