Syreverdi

Syreverdi is a Scandinavian term commonly used to describe a quantitative measure of acidity in substances. In chemistry and industry it often corresponds to the "acid value" or "acid number" of fats and oils, defined as the milligrams of potassium hydroxide (KOH) required to neutralize free fatty acids in one gram of sample. In food science and microbiology the term can also refer more generally to titratable acidity, expressed as percent of a reference acid (for example lactic or acetic acid) or in specific local units.

Measurement is typically done by titration: free acids are neutralized with a standardized base (e.g., ethanolic KOH for oils or aqueous NaOH for food liquids) using an indicator or potentiometric endpoint. Syreverdi gives different information than pH; pH measures hydrogen-ion activity in solution, while syreverdi quantifies total acid content that can be neutralized.

Syreverdi is used as a quality and process-control parameter. In edible oils and biodiesel a rising acid value indicates hydrolytic degradation or oxidation and can trigger rejection or refining; in dairy and fermented products titratable acidity helps monitor fermentation, shelf life and safety. Typical acceptable ranges depend on the product and standards (for example refined edible oils often have acid values well below 1 mg KOH/g). Factors affecting syreverdi include hydrolysis, oxidation, microbial metabolism and contamination during storage or processing.