EMULSIFIERS 15000 11250 7500 3750 0 2 2 3 % of Instathix
Figure 2: Change in viscosity with percentage of Instathix at fixed 5% oil ■ 3.5% Instathix 10% CCT - Run 1 ■ 3.5% Instathix 10% CCT - Run 2
102 3 4 17000 15250 13500 11750 10000 0 5 10 % of CCT
Figure 3: Change in viscosity with percentage of oil at fixed 3.5% Instathix ■ 3.5% Instathix 10% CCT - Run 1 ■ 3.5% Instathix 10% CCT - Run 2
101 100 100 101 Oscillation stress σ (Pa)
Figure 4: Complex modulus (measure of rigidity) versus oscillation stress on a typical Instathix cream
Natural emulsifier-thickener for oil- in-gel emulsions Instathix® (INCI: Xanthan Gum, Sodium Stearoyl Lactylate, Tapioca Starch, Algin) from Alchemy Ingredients – hereafter referred to as the emulsifier-thickener ingredient - combines powdered ingredients to give a stable, smooth texture without long mixing times. It combines a gum blend of xanthan gum and sodium alginate with the anionic emulsifier sodium stearoyl lactylate (SSL). The addition of tapioca starch gives
a smooth, silky afterfeel combined with extra stabilisation via a Pickering effect. The emulsifier-thickener ingredient, when used at the recommended level with an oil level of between 1 and 16%, gives enough emulsification and thickening to form a stable structure, holding oil droplets permanently in place to form an oil-in-gel emulsion (Figure 1). A further benefit of using SSL is the part it
plays in enhancing the natural moisturising factor (NMF) of the skin. Lactic acid is a crucial part of the NMF and SSL releases this gradually over time, helping to keep the skin moisturised long term. It also has the function of complexing with starch, keeping it in its gelled, rather than crystalline form. This means the tapioca starch remains in
a gelled state, making the system smooth and creamy. This is also why SSL is commonly used in baking, particularly as an additive in bread. The starch in bread remains in a hydrated, gelled form keeping the bread fresher for longer.
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90 80 70 60 50 40 30 20 10 0
100 101 Oscillation stress σ (Pa)
Figure 5: Phase angle (measure of elasticity) versus oscillation stress on a typical Instathix cream
How to use the emulsifier-thickener ingredient SSL is activated at 60°C, therefore the emulsifier-thickener ingredient must reach this temperature to create the oil-in-gel emulsion. 1 part of the emulsifier-thickener ingredient will emulsify four parts of oil, up to a maximum of 4% of the emulsifier-thickener ingredient with 16% oil. Higher levels of oil can be incorporated with the addition of other ingredients such as glyceryl stearate, cetearyl alcohol or other co-emulsifiers. Due to the hydrating feel of the resulting cream-gel it may not be necessary to add higher levels of oil, the richness can also be increased by using a proportion of butters and other solid emollients to the formulation, which will increase viscosity as well. Glycerine or other glycols can be added to
increase the humectancy of the formulation. The viscosity of the emulsifier-thickener ingredient at different levels, and with different amounts of oil (Caprylic/Capric Triglyceride) are shown in Figures 2 and 3.
Method of mixing There are several different ways to mix the emulsifier-thickener ingredient. In the lab, it can be convenient to pre-disperse the emulsifier-thickener ingredient in the oil phase to wet it first before water is added. If butters, solid emollients or waxes are in
the formula, these can be melted in the oil first. Hot water can then be introduced and the mixture held at 70°C for several minutes to
completely hydrate the product. A cream will instantly form, however a
better texture and smaller oil droplet size will result if the mixture is homogenised for a few minutes, followed by slow stirring on an overhead mixer while the product cools. Other methods have been trialled, including an all-in-one method where all ingredients apart from those that are heat sensitive are put in a vessel and heated to 70°C, then homogenised and cooled as before. Alternatively a pre-mix concentrate could be made with a portion of the water to make a concentrated emulsion, then the rest of the water added cold. It is important to consider methods
involving the least amount of energy input possible due to current high energy and processing costs. A start-to-finish cold process using the emulsifier-thickener ingredient is not possible, but there are many ways energy can be reduced compared with traditional emulsifiers and thickeners as the product does not need a long hydration time and forms instantly once the mixture is at the correct temperature.
Textures with the emulsifier- thickener ingredient Formulations with the emulsifier-thickener ingredient have a set, shear thinning rheology with emulsions having a fairly high rigidity and elasticity. When a typical emulsion is subject to an oscillation stress sweep, the emulsion behaves as a solid at low shear, yielding to a
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Complex modulus G* (Pa)
Viscosity Cps
Phase angle δ (°)
Viscosity Cps
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