Free acidity determination

Free acidity refers to the amount of free fatty acids present in a fat, whether it be vegetable oil, butter, animal fat, or a derivative product. This parameter is a key quality indicator, used to assess the freshness, stability, rancidity, or oxidative degradation of a lipid product. It is also crucial for regulatory compliance of food products and cosmetic formulations.

High free acidity is generally associated with altered organoleptic properties (taste, smell), decreased nutritional value, and possible microbiological instability.

Why measure free acidity?

Measuring free acidity is essential in many situations:

• Quality control of edible oils (olive, sunflower, rapeseed, etc.);
• Storage monitoring based on storage time or temperature;
• Verification of conformity according to ISO standards, Codex Alimentarius or European regulations;
• Assessment of rancidity or aging of fats and butters;
• Control of raw materials in the processing or cosmetics industries;
• Validation of the stability of essential oils and plant lipid extracts.

Analytical method: titrimetry according to ISO 660

The analysis of free acidity is based on a titrimetric method, also called acidimetry. It consists of titrating the free fatty acids present in the matrix using a standardized solution of sodium hydroxide (NaOH), in the presence of a colored indicator.

ISO 660 governs the conditions for carrying out this method, guaranteeing the reproducibility and comparability of the results. Acidity is generally expressed as a percentage of oleic acid (or other equivalent depending on the matrix analyzed).

In certain specific cases, complementary methods such as pH measurement or infrared spectroscopy may be used as support.

Affected matrices

Free acidity analysis is applicable to a wide variety of natural or processed matrices, including:

• Raw or refined vegetable oils (olive, flaxseed, soybean, peanut, rapeseed, etc.);
• Animal fats (lard, tallow, clarified butter);
• Essential oils intended for food or cosmetic use;
• Cosmetic products containing a lipid base (balms, hair care products, creams);
• Technical ingredients derived from biomass (esters, biodiesel, fatty extracts, etc.).

Further analyses recommended

For a complete characterization of fats, it is advisable to combine free acidity analysis with other services available in the YesWeLab catalog , such as:

• Peroxide value : a measure of the primary oxidation of lipids;
• Iodine index : saturation/double bonds of fatty acids;
• Saponification index : evaluation of the average molar mass of fatty acids.

Why choose YesWeLab?

At YesWeLab, we provide a network of partner laboratories specializing in physico-chemical analyses, selected for their expertise, accreditations (ISO 17025, COFRAC) and methodological rigor.

Thanks to our digital platform, you can:

• Order your analyses online quickly;
• Describe your samples and requirements precisely;
• Track your results and reports with complete transparency;
• Benefit from tailored technical support, in conjunction with our scientific experts.

Add the dosage to your quote now

Whether you are an oil producer, cosmetic formulator or food processor, measuring free acidity is an essential analysis to guarantee the quality, conformity and durability of your products.

Add this service to your quote or contact us for a personalized study.