Shelf life and stability of cosmetic formulation with natural oils
Asked by: aromaandco
On: June 17, 2015
Product Type:
Cosmetics
Question
I have a cosmetic formulation containing the following ingredients:
- Cold-pressed coconut oil
- Rice bran oil
- Butter (unspecified type, but likely plant-based or similar)
- Vitamin E
- Phenoxyethanol
and other unspecified ingredients.
I understand that the shelf life is determined by the ingredient with the shortest lifespan, which I believe are the oils and butter due to oxidation (rancidity).
- What is the expected shelf life of this formulation, considering these ingredients?
- How do the specific types of oils (cold-pressed vs. refined/fractionated) affect the shelf life?
- What roles do Vitamin E and Phenoxyethanol play in preserving the product, particularly regarding oxidation and microbial growth?
Answer
Determining the exact shelf life of a cosmetic product requires stability testing (accelerated aging tests). However, based on your formulation, here are some points to consider:
- Limiting Factor: As mentioned previously, the shelf life is determined by the ingredient that degrades fastest. In your formula, the natural oils and butter (cold-pressed coconut oil, rice bran oil, butter) are most susceptible to oxidation (becoming rancid), which is likely the limiting factor for shelf life, especially without strong antioxidant protection.
- Cold-Pressed Oils: Cold-pressed coconut oil and rice bran oil are less stable than refined or fractionated oils and are more prone to oxidation.
- Antioxidants: You mentioned "no antioxidant" but listed Vitamin E, which is an antioxidant. Vitamin E can help slow down oxidation, but its effectiveness depends on the concentration and the overall formulation. If there is truly no antioxidant (including Vitamin E), the oils will oxidize very quickly, resulting in a much shorter shelf life than 1 year. If Vitamin E is present, it offers some protection, but it might not be sufficient to guarantee 1 year, especially for cold-pressed oils.
- Preservative: Phenoxyethanol is a preservative that prevents microbial growth (bacteria, mold, yeast). It does not prevent oxidation or rancidity.
- 1-Year Estimate: A shelf life of 1 year might be achievable under optimal storage conditions (cool, dark place) with some antioxidant protection (like Vitamin E), but it is not guaranteed without conducting proper stability testing. It's possible the oils could become rancid sooner.
- Recommendation: To accurately determine the shelf life and ensure product quality and safety over time, it is highly recommended to perform stability testing. Monitor the product for changes in smell (rancidity), color, and texture over time.