Free acidity determination

Free acidity refers to the amount of free fatty acids present in a fat, whether vegetable oil, butter, animal fat, or a derived 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 foodstuffs or cosmetic formulations.

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

Why measure free acidity?

The measurement of free acidity is essential in many situations:

• Quality control of edible oils (olive, sunflower, rapeseed, etc.);
• Conservation monitoring based on storage duration or temperature;
• Verification of compliance with 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 standard

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

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

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

Affected matrices

The free acidity assay applies to a wide variety of natural or processed matrices, including:

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

Further analyses recommended

For a complete characterization of fats, it is relevant to couple the free acidity dosage with other services available in the YesWeLab catalog , such as:

• Peroxide index : measure of primary oxidation of lipids;
• Iodine value : 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 physicochemical analyses, selected for their expertise, their accreditations (ISO 17025, COFRAC) and their methodological rigor.

Thanks to our digital platform, you can:

• Quickly order your analyses online;
• Describe your samples and requirements accurately;
• Track your results and reports transparently;
• Benefit from tailor-made technical support, in conjunction with our scientific experts.

Add dosage to your quote now

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

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