Broad-Spectrum Preservation System for O/W Emulsions
Choosing and validating a preservation system is one of the most technically demanding aspects of cosmetic formulation. This guide covers the selection logic, combination strategies, and challenge testing requirements for a broad-spectrum preservation system suitable for O/W emulsions intended for the EU market. No single preservative is effective against all microorganisms — multi-component systems are standard practice.
Target Application
O/W emulsions (creams, lotions, serums) for EU market
Key Properties
- Broad-spectrum efficacy (bacteria, yeast, mould)
- Compliant with Annex V of EU Regulation 1223/2009
- pH-compatible (effective at pH 4.5–6.5)
- Consumer-acceptable safety profile
Ingredient List
| INGREDIENT | % |
|---|---|
| Potassium Sorbate | 0.2–0.3% |
| INGREDIENT | % |
|---|---|
| Sodium Benzoate | 0.3–0.5% |
| INGREDIENT | % |
|---|---|
| Ethylhexylglycerin | 0.2% |
| Benzyl Alcohol | 0.5–1.0% |
| INGREDIENT | % |
|---|---|
| Phenoxyethanol | 0.7–1.0% |
Percentages are by weight unless otherwise noted. “q.s.” = quantity sufficient to reach 100%.
Manufacturing Process
- 1
Select your primary preservative based on your target pH and microbiological risk profile (see below).
- 2
Identify gaps in spectrum: phenoxyethanol alone is weak against gram-negative bacteria (Pseudomonas) — you need a booster or second preservative.
- 3
Check pH compatibility: sodium benzoate and potassium sorbate are only active in their undissociated (acid) form — only use if your formulation pH is ≤5.5 (benzoate) or ≤6.5 (sorbate).
- 4
Calculate total permitted concentrations relative to EU Annex V limits — do not stack preservatives beyond permitted maxima.
- 5
Manufacture a pilot batch with the preservation system and submit for ISO 11930 challenge testing (PET — Preservation Efficacy Test).
- 6
Acceptance criterion: Category 2 (rinse-off) or Category 1 (leave-on) per ISO 11930. Adjust system if any organisms fail.
- 7
Perform stability testing at 40°C / 8 weeks — preservative efficacy can degrade with heat or if pH drifts.
Regulatory Notes
- EU Annex V lists all permitted preservatives with maximum concentrations — any preservative not on this list is not permitted in EU cosmetics
- Benzyl alcohol requires label declaration as fragrance allergen (1223/2009 Annex III) if above 0.001% in leave-on or 0.01% in rinse-off
- Parabens: several are restricted or banned for use in products for children under 3 or in the nappy area — avoid if targeting baby care
- COSMOS-certified formulas: only preservatives listed in the COSMOS-standard permitted preservatives list may be used
- ISO 11930:2019 is the current challenge test standard — ensure your testing lab is using this version, not the previous 2012 edition
Formulator Tips
- Never assume a system that works in one formula will work in another — different emulsifiers, proteins, and pH levels all affect preservative activity
- High concentrations of some emollients (especially esters) can partition preservatives into the oil phase, reducing aqueous-phase efficacy
- Water activity (Aw) matters — higher glycerin concentrations (>10%) reduce Aw and can aid preservation, reducing reliance on chemical preservatives
- Chelating agents (EDTA, gluconic acid) disrupt gram-negative outer membranes and dramatically improve phenoxyethanol efficacy against Pseudomonas
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