184 TEXTURES n Viscosity - 1 month n Oil droplet size (µm) - 1 month


100 80 60 40 20 0


40% oil 50% oil 60% oil Figure 2: Effect of oil concentration on droplet size and viscosity.


The addition of 10% of water to the glycerine phase has a negative effect as it leads to increasing droplet sizes and transparency of the formula will be lost (see paragraph 5). Adding 5% of water does help to decrease the viscosity when making a combination with L70-C. A slight increase in droplet size is observed, but this has no negative effect on the transparency. To limit the water content in the formula, it is preferred to work with 99% pure glycerine (Fig 3).


Effect of manufacturing temperature


All combinations can be prepared by hot and semi-cold process (adding a cold oil phase). Combinations with L70-C sucrose laurate can also be prepared cold, which is time and cost effective (Fig 4).


Transparency: how to influence In paragraph 3 we discussed the effect of water on the formulation. This test has also shown that the formulations made with vegetable oils will not be transparent any more when adding water. Therefore we zoomed in on the refractive index of the glycerine- and oil phase. Transparency can be obtained by matching refractive indices of the oil and glycerine phases. Depending on the desired oil, you can choose to adjust the


200 180 160 140 120 100 80 60 40 20 0


SP70-C PS750-C Figure 4: Effect of manufacturing temperature. PERSONAL CARE EUROPE SP70/L70-C PS750/L70-C 1.0 n SP70-C n PS750-C n SP70-C/L70-C n PS750-C/L70-C n Average droplet size 0.5 0.0


180 160 140 120 100 80 60 40 20 0


0% water 5% water 10% water Figure 3: Effect of water on droplet size and viscosity. Table 3: Influencing transparency


Refractive index


Glycerine Phase


glycerine + 2% SP70-C + 0% water 1.47 glycerine + 2% SP70-C + 5% water 1.45 glycerine + 2% SP70-C + 10% water 1.43 Oil Phase


vegetable oil caprylic/capric triglyceride


1.47 1.45


refractive index with water. When using a combination with L70-C, the 50% water content of the product needs to be taken into account (Table 3).


Conclusion on gel-to-milk O/G emulsions The tested sucrose esters all give narrow droplet size concentrated O/G emulsions with average oil droplet sizes of 0.3 - 0.5 µm, which are made by using a high shear mixer. By using just 2% of a high HLB sucrose ester it is already possible to produce a gel- to-milk concept containing 60% of oil. Viscosity can be influenced by combining


sucrose stearate or -palmitate with sucrose laurate or by decreasing the amount of oil.


n Cold n Semi-cold n Hot Depending on the used grades, cold


process is possible. Hot and semi-hot process are always possible. Transparency can be influenced by matching refractive indices of the oil and glycerine phase. This can be done by changing the oils and adding water. Too much water has a negative effect on the transparency and droplet size. An extra benefit is the possibility to develop preservative-free formulations due to the extremely low water content of the O/G emulsion: below 0.6 Aw.


The gel-to-milk concept is very suitable for making interesting new concepts such as makeup cleansers, scrubs, massage balms, bath jellies, shower gels, hair treatments and many more possibilities.


One step further: Diluted gel-to- milk concentrated emulsions An easy manufacturing technique for stable thin liquid emulsions has been developed by using the gel-to-milk O/G concentrated emulsions as an intermediate step. Oil in water emulsions with very small droplet sizes of 0.3 µm can be obtained when produced via this simple intermediate concentrated O/G emulsification step. The first part of the production method is the same as when you produce a gel-to-milk formula. After emulsification the emulsion is diluted with water containing a stabiliser. The optimum ratio of oil/glycerin for this concept is 50/50 (Table 4). Figure 5 shows the droplet size distribution of an emulsion prepared through different manufacturing techniques. Oil in water emulsions with very small droplet sizes of 0.3 - 0.5 µm (blue curve) can be obtained when produced via the simple intermediate concentrated O/G emulsification step. The standard way of producing oil in water emulsions with high shear homogenising equipment results in macro emulsions with droplet sizes of about 10 µm (green curve). Additional high pressure homogenisation would be necessary to obtain smaller droplets (red curve), but this process results in a higher


April 2020


2.5 2


1.5 1


0.5 0


Viscosity (pa.s) Viscosity (pa.s)


Oil droplet size (µm) Viscosity (pa.s)


Oil droplet size (µm)


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