Comparison of Sodium Stearoyl Lactylate and Sodium Lauroyl Lactylate

Both Sodium Stearoyl Lactylate and Sodium Lauroyl Lactylate are emulsifiers derived from lactic acid and a fatty acid. However, the key difference lies in the fatty acid used:

• Sodium Stearoyl Lactylate is derived from stearic acid (a longer fatty acid chain).
• Sodium Lauroyl Lactylate is derived from lauric acid (a shorter fatty acid chain).

This difference in fatty acid chain length results in different properties and primary uses:

Sodium Stearoyl Lactylate

• Primary Function: Primarily used as a water-in-oil or oil-in-water emulsifier. It is known for its ability to create stable emulsions and also provides good skin moisturizing and conditioning properties.
• Solubility & Processing: Soluble in oil and requires heating (typically 70-80°C) to incorporate into the oil phase. It is often recommended to be used with thickeners like Cetearyl Alcohol or Cetyl Alcohol for optimal formulation stability.
• Typical Use Rate: 1-3%.
• Applications: Commonly used in leave-on products like creams, lotions, and moisturizers where stable emulsions and skin feel are important.

Sodium Lauroyl Lactylate

• Primary Function: Classified as a gentle anionic surfactant. While it functions as an emulsifier (helping to emulsify oil in water), it also acts as a viscosity builder, foam booster (in rinse-off products), stabilizer, and skin feel enhancer. It is known for being mild to the skin.
• Solubility & Processing: Can be dispersed in water-oil mixtures. It is thermally stable and suitable for cold processing conditions, although it can also be used in heated formulations.
• Typical Use Rate: 0.5-5%.
• Applications: Versatile ingredient used in both rinse-off products (shampoos, body wash, cleansers) and leave-on products (creams, lotions, conditioners, sunscreens).

Can they be used interchangeably in a moisturizing cream?

While both ingredients can function as emulsifiers in a moisturizing cream, they are not directly interchangeable without potentially affecting the final product's characteristics and stability.

• Sodium Stearoyl Lactylate is more specifically designed as a primary emulsifier for creams and lotions, contributing significantly to emulsion stability and skin feel, often requiring heating and co-ingredients for best results.
• Sodium Lauroyl Lactylate is a more multi-functional ingredient that, while emulsifying, also brings surfactant properties (though gentle) and can impact viscosity and feel differently. Its suitability for cold processing is also a distinct difference.

Substituting one for the other would likely require adjusting the formulation, potentially changing other ingredients (like thickeners or co-emulsifiers), and conducting stability testing to ensure the cream remains stable and performs as intended. Therefore, they should not be swapped one-to-one in an existing formula.