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When is heat required for emulsions?
I am a bit confused on when heat is needed for emulsions. I have watched several emulsification processes and some chemists never heat their water and oil phases.
I prefer to not to use heat as I am worried of destroying flavonoids in my herbal extracts that I add to the water phase.
Can anyone enlighten me?
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8 Replies
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If you use cold-process emulsifiers, then you will not need heat. Otherwise, heat is a necessity with the great majority of emulsifiers.
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Actives are added in the cool-down period when using hot process. It is not a problem.
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You can use cold emulsifiers which tend to be more expensive that usual emulsifiers and you can only use liquid oil faze, or do as Belassi said, add ingredients which are not stable in higher temperature when the emulsion is cooling.
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liquid emulsions (e.g. cosmetic products) are formed when both the oil and water phase are liquid: if there are solid materials in the oil phase, they need to be heated to a high enough temperature to melt
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I will be heating both the water and oil phases to 70° C and then once the emulsion cools down to under 50° C I will add my herbal extracts and Allantoin.
I am assuming this will not interfere with the emulsion because emulsion only involve water and oil, does this mean that all water soluble ingredients can be added during or after emulsion? Since the water concentration in my formula is higher than oil, there should be enough water for the ingredients to disperse to anyway?
Is there an advantage in placing the ingredients into the water phase before emulsion?
Thanks
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You want to include as much of the water phase as possible in the hot part of the process to get best stability. Check your active components for temperature sensitivity. 50C may be too high for some - for instance, polypeptides will be cooked at that temperature and made useless. And you would not want to add Vitamin C at 50 degrees, either.
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If it makes you feel better, there will be little noticeable difference even if you breakdown the flavonoids in your herbal extracts. There is little scientific evidence demonstrating their effectiveness in topical products.
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Is there an advantage in placing the ingredients into the water phase before emulsion?
Allantoin is heat stable and dissolves better at higher temperatures, so you can add it in the water phase. Up to 0,5% will not precipitate once the emulsion is cooling down.
About the herbal extracts: which one do you use? Perhaps if you give names, people can help you better (e.g. licorice extract).
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