Correct Procedure for Oil-in-Water Cream Formulation and Cooling
Question
Based on issues with Oil-in-Water cream separating during the cooling phase, please advise on the correct procedure:
- What is the recommended mixing time at high heat (excluding the cool-down phase)?
- What is the correct cool-down method: letting it cool slowly on the switched-off Hot plate, or removing it completely from heat?
- Is stirring necessary during the cool-down phase, or only when adding fragrance after the temperature drops?
Answer
Correct Procedure for Oil-in-Water Cream Formulation
Based on your questions and the previous discussion regarding the issue with your Oil-in-Water cream separating during the cooling phase, here is the recommended procedure:
1. Mixing Time at High Heat
There is no fixed time for mixing at high heat. The key is to ensure that the mixture is completely emulsified while hot. You can test this by taking a small amount and spreading it on your skin; there should be no grainy texture or separation visible. Once fully emulsified, continue mixing for an additional 10 minutes to ensure stability.
2. Correct Cooling Down Method
After turning off the heat, the beaker should remain on the hot plate while you continue stirring. This allows the mixture to cool down gradually. Rapid cooling, such as removing the beaker from the heat source immediately, can cause the emulsion to break, especially with high oil percentages like 36%. In large-scale production, double-jacketed pots or using substances like Glycerin in the outer layer are common methods to control and slow down the cooling rate.
3. Stirring During Cooling Down
Yes, continuous stirring is necessary during the cooling phase until the temperature drops sufficiently (typically below 40°C) before adding heat-sensitive ingredients like fragrance. Continuous stirring helps maintain the emulsion stability as the cream cools and thickens.
