Preservatives for Emulsions

Preservatives are crucial in emulsion formulations (both oil-in-water and water-in-oil) to prevent microbial contamination, which can cause spoilage, separation, and potential health risks. Since emulsions contain a water phase, they are particularly susceptible to bacterial and fungal growth.

Common Preservatives for Emulsions

Many broad-spectrum preservatives are suitable for use in emulsions. These often include combinations of ingredients to cover a wide range of microorganisms. Examples of preservatives that can be used include:

• NaturePreserve™ LB2: A natural origin preservative effective against bacteria and fungi, particularly at lower pH.
• Global Guard™ 221: A broad-spectrum, water-soluble preservative effective in a wide pH range (2-7).
• Preserve-BSB™: A blend of benzyl alcohol, sodium benzoate, and potassium sorbate, effective against bacteria, mold, and yeast, suitable for formulas up to pH 5.5.
• Mild Preserved™ COS: A broad-spectrum, water-soluble preservative effective in a wide pH range (2-8) and odorless.
• NaturePreserve™ Ultra: A natural preservative blend (Gluconolactone & Sodium Benzoate) effective at pH 3-6.

It is important to choose a preservative that is compatible with your specific formula and effective at its pH range.

Different Emulsion Types (O/W vs. W/O)

While many broad-spectrum preservatives can be used in both O/W and W/O emulsions, their efficacy can depend on how they partition between the oil and water phases. Preservatives that are highly soluble in water are generally very effective in the water phase of O/W emulsions. For W/O emulsions, where the water is dispersed as droplets within the oil phase, the preservative needs to be effective within these droplets or at the interface. Some preservatives may be more suitable or require different concentrations depending on the emulsion type to ensure adequate protection in both phases.

Addition Step and Concentration

Preservatives are typically added during the cooling phase of emulsion production, usually below 45-50°C, to prevent degradation from heat. They are often added to the water phase or dispersed in the external phase (which is water in O/W emulsions). The exact step can depend on the preservative's solubility and the specific manufacturing process.

The concentration of the preservative varies significantly depending on the specific type of preservative used, the complexity of the formula, the risk of contamination, and regulatory guidelines. Based on the examples above, typical usage rates can range from 0.3% to 2.0% by weight of the total formula. It is crucial to perform a challenge test on your final product formulation to confirm that the chosen preservative and its concentration are effective in preventing microbial growth under realistic conditions.