Preserving Hydrosols Naturally: Potassium Sorbate, Citric Acid, and Sodium Benzoate
Hydrosols—those fragrant, water-based distillates from plants—are a gentle yet potent part of herbal wellness and skincare. However, as water-based products, hydrosols are also susceptible to microbial growth. That’s where natural and food-grade preservatives come in. In this post, we explore two common preservation systems for hydrosols:
Potassium Sorbate + Citric Acid
Sodium Benzoate + Potassium Sorbate
We’ll break down how they work, their differences, recommended concentrations, and how to use them effectively to keep your hydrosols safe and shelf-stable.
Why Do Hydrosols Need Preservatives?
Hydrosols contain water and trace organic materials, making them vulnerable to bacterial, yeast, and mold contamination—especially after opening. Different hydrosols have different properties. Some herbs have strong antibacterial and antiseptic properties such as lavender, oregano, thyme, which helps them have longer shelf life. Some herbs don’t have the properties such as cucumber and their shelf life will become shorter. Refrigeration can slow growth, but it doesn’t guarantee protection. That’s why adding a safe preservative is essential for hydrosols that are stored at varied or high temperature or sold commercially.
1. Potassium Sorbate + Citric Acid
How It Works
Potassium sorbate is a mild, broad-spectrum preservative that inhibits mold, yeast, and some bacteria. It’s commonly used in food, beverages, and personal care products.
Citric acid isn’t a preservative on its own but is used to lower pH, which enhances the effectiveness of potassium sorbate. Potassium sorbate works best in acidic conditions (pH below 4.5).
Typical Use Concentration
Potassium sorbate: 0.1–0.3%
Citric acid: Adjust as needed to bring the pH down to 3.5–4.2, depending on your hydrosol’s starting pH.
Pros
Mild, skin-friendly
Food-grade and generally recognized as safe (GRAS)
Suitable for products with a clean-label appeal
Cons
Not effective above pH 5.0
May not be sufficient against some bacteria unless pH is strictly controlled
Best For:
DIY and artisan hydrosols where maintaining a low pH is acceptable
Products aimed at sensitive skin or a clean, minimalist formula
2. Sodium Benzoate + Potassium Sorbate
How It Works
Sodium benzoate is effective against yeast, bacteria, and some fungi—especially in acidic environments.
When paired with potassium sorbate, the combination provides broad-spectrum antimicrobial protection, making it a popular choice in both food and skincare.
Works synergistically when pH is below 5.
Typical Use Concentration
Sodium benzoate: 0.1–0.2%
Potassium sorbate: 0.1–0.2%
pH must be adjusted to < 5.0 using citric acid or another acidifier.
Pros
Broader spectrum than potassium sorbate alone
Good safety profile (widely used in food and cosmetics)
Suitable for commercial products
Cons
May cause irritation at high concentrations
Less effective if pH is not properly adjusted
Some consumers avoid sodium benzoate due to sensitivity or preference
Best For:
Hydrosols that will be stored at high and varied temperature
Products sold commercially or with longer shelf-life requirements
Summary: Choosing the Right Preservative System
Testing and Best Practices
Always measure pH of your final hydrosol product. A digital pH meter or high-quality test strips are essential tools.
Preservatives should be added once the hydrosol has cooled to room temperature (if freshly distilled).
Conduct microbial testing if you're producing hydrosols for sale or long-term storage.
Store in sterile, opaque containers to reduce light and contamination risks.
Final Thoughts
Preserving your hydrosols doesn't mean compromising their purity or gentleness. By using safe, effective, and well-researched preservative systems like potassium sorbate/citric acid or sodium benzoate/potassium sorbate, you can ensure your hydrosols remain fresh and safe for weeks or even months.
For wellness creators, herbalists, or small businesses, understanding the science of preservation means more than safety—it’s about trust, quality, and care.
LETIME offers easy-to-use herbal extractors and tools that make distilling and infusing your botanical creations simple and reliable. Whether you're crafting a rose hydrosol for skincare or a lavender blend for calming sprays, we help you do it the right way—from plant to product.
Disclaimer: The information provided in this article is for educational purposes only and does not constitute professional advice. While the preservatives mentioned (potassium sorbate, citric acid, sodium benzoate) are widely regarded as safe and commonly used in food and cosmetic formulations, proper handling, pH adjustment, and hygiene practices are essential to ensure product safety. Individuals and businesses creating hydrosols for personal use or commercial sale should perform their own microbial testing and comply with local cosmetic and labeling regulations. Always consult a qualified cosmetic chemist or regulatory expert for guidance specific to your formulation or market.
