Overview
ISO 13082:2011 specifies a laboratory method for the determination of lipase activity in commercial pregastric lipase preparations and rennet paste of animal origin. The procedure quantifies activity in international lipase units (ILU) by measuring the release of butyric (butanoic) acid from the substrate tributyrin under defined conditions. It is intended for quality control, specification and comparative testing of lipase-containing processing aids used in cheese making and enzyme-modified dairy products.
Key topics and technical requirements
- Principle: Hydrolysis of triglyceride ester (tributyrin) by lipase; free fatty acids (butyric acid) are titrated in a pH‑stat with NaOH. Titrant consumption during a defined interval (last 10 min of a 15‑min run) is used to calculate ILU.
- Unit definition: 1 ILU = enzymatic activity that releases butanoic acid at 1.25 µmol/min under the specified test conditions (note: a small systematic error exists because ~4% of butyric acid is not dissociated and not titratable).
- Critical conditions:
- Reaction temperature: 42.0 °C ± 0.5 °C (reaction vessel)
- Titration pH: 6.20 (stabilized during initial period)
- Typical titrant: 0.025 mol/L NaOH (0.010 mol/L recommended for low-activity samples or manual titration)
- Substrate and reagent examples: tributyrin, sodium caseinate, lecithin, liquid paraffin
- Sample preparation: Procedures for liquid lipase, powdered lipase and rennet paste (stomacher homogenization, pH adjustment to ~8.5 for powders/pastes).
- Instrumentation: pH-stat titrator (automated preferred), thermostated reaction vessel, water bath, blender/Ultraturax, stomacher for pastes.
- Quality controls: Include a control sample of known activity in each series; use blanks for low-activity samples. Report equipment and dilution factors.
Applications and users
- Dairy laboratories performing quality control and batch release testing of pregastric lipases and rennet pastes.
- Cheese manufacturers (e.g., producers of Romano, Provolone, Asiago and other Italian‑type cheeses) monitoring lipase dosing for consistent flavor development.
- Enzyme suppliers and R&D groups characterizing product potency.
- Regulatory or compliance testing where accurate measurement of lipase activity is required for labeling, specification or process control.
Related standards
- ISO 707 / IDF 50 - recommended sampling for milk and milk products (referenced for sample representativity)
- FCC/IV methods - earlier lipase test methods served as a model
- IDF Bulletin 294 - context on use of lipases in cheese and enzyme-modified dairy products
Keywords: ISO 13082, lipase activity, pregastric lipase, milk and milk products, tributyrin, pH‑stat, ILU, rennet paste, cheese processing.