Iodine Value in Plant Oils and Butters

In this post, we talked about the Importance of Triglycerides (plant oils and buttters) in Skin and Hair Care. It’s important to understand the iodine value when choosing and formulating with plant oils and butters.

What is the Iodine Value?

The iodine value (also called iodine number) is a measure of the degree of unsaturation in oils and butters. It indicates how many grams of iodine can react with 100 grams of oil. In simpler terms, it reflects how many double bonds are present in the fatty acids that make up the oil.

• High iodine value → more double bonds, higher unsaturation.

• Low iodine value → fewer double bonds, more saturation.

This single number helps cosmetic formulators understand an oil’s stability, shelf life, and functionality in formulations.

Why the Iodine Value Matters in Formulation

1. Shelf Life & Rancidity
   Oils with high iodine values (very unsaturated) are prone to oxidation and rancidity. This shortens the product’s shelf life unless antioxidants are used.

2. Texture & Function
   Saturated oils (low iodine value) tend to be firm and stable, making them ideal for butters, balms, and products that require structure. Unsaturated oils (high iodine value) are lighter, spread easily, and provide skin-softening benefits but are less stable.

3. Formulation Strategy
   Knowing the iodine value helps a formulator decide how to balance oils—butters for both performance and stability. For instance, blending a high-iodine-value oil with a stable butter can improve shelf life.

High vs. Low Iodine Value: What It Means

• High Iodine Value (>100)

  • Very unsaturated oils (e.g., flaxseed, hemp, rosehip).

  • Lightweight, quick-absorbing, rich in essential fatty acids.

  • Susceptible to rancidity. Shelf life: ~6 months to 1 year.

• Moderate Iodine Value (80–100)

  • Oils with balanced stability and skin benefits (e.g., sunflower, sesame).

  • Shelf life: ~1–2 years.

• Low Iodine Value (<70)

  • More saturated oils and butters (e.g., coconut, cocoa butter, shea).

  • Stable, longer shelf life, solid texture.

  • Shelf life: 2–3 years or more.

• High iodine value = More unsaturated bonds = More prone to oxidation and rancidity.
• Low iodine value = More saturated bonds = More stable and longer shelf life.

Why Iodine Level Matters in Cosmetic Formulation

1. Shelf Life and Stability
   Oils with high iodine values oxidize faster, leading to rancid smells, discoloration, and loss of beneficial properties.
2. Product Performance
   Oxidized oils can irritate the skin, change a product’s texture, and reduce the effectiveness of active compounds.
3. Formulation Strategy
   • For products meant to last 12+ months, using primarily low-to-moderate iodine value oils increases stability.
   • High iodine value oils can still be used for their skin benefits but should be paired with antioxidants (e.g., Vitamin E, rosemary extract) and packaged in air-tight, opaque containers.
4. Preservation Planning
   Even though antioxidants can slow oxidation, knowing the iodine value helps determine how much protection is needed.

What Influences the Shelf Life of Plant Oils and Butters

1. Storage Before Purchase (Supplier’s Storage Conditions)

The shelf life of an oil or butter doesn’t start fresh when you buy it—it begins the moment the oil is extracted and processed.

• If a supplier has stored the oil or butter for several months before selling, your remaining shelf life may be significantly reduced.

• Oils that are not stored under optimal conditions (cool, dark, airtight, and away from heat sources) can already be partially oxidized before you receive them.

Tip for formulators: Ask suppliers about the date of production or date of pressing/refining of the oil or butter, not just the expiration date.

2. Supplier Storage Methods

The way suppliers handle their bulk oils and butters has a big impact:

• Temperature: Cold storage (refrigeration) greatly slows oxidation. Room-temperature or warm storage accelerates it.

• Light Exposure: Oils exposed to light degrade faster. Amber, opaque, or UV-protective containers extend life.

• Air Exposure: Oils kept in partially filled containers may oxidize more quickly due to oxygen exposure. Nitrogen-flushed containers extend stability.

Tip for formulators: Always choose suppliers with good storage practices (e.g., refrigerated storage, sealed containers).

3. Fatty Acid Profile and Manufacturer Variability

The exact fatty acid profile of an oil can vary depending on:

• Plant variety or cultivar.

• Region and climate where the plant is grown.

• Processing method (cold-pressed, refined, deodorized, etc.).

This means one supplier’s batch of rosehip oil might have a slightly different iodine value—and therefore a different stability—than another’s.

Tip for formulators: Always request the Technical Data Sheet (TDS) or Certificate of Analysis (COA) for the specific batch you’re purchasing. This is the only way to know the exact fatty acid counts and iodine value.

4. When Shelf Life Really Starts

Shelf life estimates in tables and literature are guidelines. The actual countdown for your formulations begins the moment you receive the oil or butter. From that point forward, proper storage on your end is critical to maximize stability.

Best practices for formulators:

• Store oils and butters in cool, dark conditions.

• Use amber or opaque containers whenever possible.

• Keep containers tightly sealed to minimize oxygen exposure.

• Add natural antioxidants (like Vitamin E or rosemary extract) to help extend the life of unstable oils.

• Label each oil with the date received and track usage accordingly.

Shelf life is not a universal number, it’s dynamic. It depends on how long the supplier stored the oil before selling, how well both the supplier and you store it, and the unique fatty acid composition of that particular batch. For formulators, the “real shelf life” clock starts ticking when the raw material arrives in your lab.

Approximate Shelf Lives of Plant Oils and Butters by Iodine Value

Download this Chart

How to Check the Iodine Value Before Purchasing

As a cosmetic formulator, it’s essential to know the iodine value before you buy raw materials. Here’s how:

1. Supplier Specifications

   • Reputable suppliers provide a Technical Data Sheet (TDS) or Certificate of Analysis (COA).

   • Look for the iodine value range (it may vary slightly by batch).

2. Reference Standards

   • Use published resources such as the CIR (Cosmetic Ingredient Review), pharmacopoeias, or cosmetic chemistry databases.

3. Ask the Supplier

   • If iodine value is not listed, request it directly. It demonstrates professionalism and ensures product stability.

4. Third-Party Testing

   • For critical formulations, oils can be lab-tested for iodine value and peroxide value (oxidation indicator).

Key Takeaway for Cosmetic Formulators

The iodine value is more than a chemistry number—it directly affects formulation stability, shelf life, and product performance. By checking iodine values before purchase, you can choose the right oils and butters, prevent rancidity issues, and craft formulations that deliver both efficacy and longevity.

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