ISO 23058:2006

Overview

ISO 23058:2006 (IDF 199:2006) specifies a laboratory method for determining the total milk‑clotting activity of ovine (sheep) and caprine (goat) rennets - including liquid rennets, powdered rennets and rennet paste. The method measures clotting time on a standard milk substrate prepared with calcium chloride (0.5 g/L, pH ≈ 6.5) and reports activity relative to international bovine reference standards in International Milk‑Clotting Units (IMCU). ISO 23058:2006 is intended for producers, control laboratories and research groups who need reproducible measures of milk‑clotting activity for cheesemaking quality control, product specification and regulatory compliance.

Key topics and requirements

• Principle: Determine the time to visual flocculation of the standard milk substrate and compare to a bovine reference standard with defined enzyme composition (75% calf chymosin : 25% bovine pepsin).
• Reference standards: Use calf and adult bovine rennet reference powders (primary standards, ~1 000 IMCU/g indicated on certificates) for calibration and relative measurement.
• Substrate and reagents: Standard milk substrate prepared using CaCl2 working solution (0.5 g/L); use low‑heat, low‑fat spray‑dried milk powders of suitable renneting quality.
• Sample forms: Procedures for preparing liquid, paste and powdered ovine/caprine rennet test solutions are specified.
• Apparatus & precision: Requires precision pipettes, calibrated thermometers and pH meters; the standard includes precision information from interlaboratory trials (repeatability and reproducibility).
• Calculation & expression: Results expressed relative to the reference powders and reported in IMCU; procedures for preparing reference working solutions and test dilutions are defined.
• Storage & handling: Reference powders stored protected from moisture and light at −18 °C (short transport at ambient temperature permitted).

Applications and users

• Dairy product manufacturers and cheesemakers assessing coagulant strength for recipe formulation and process control.
• Rennet producers and suppliers validating product potency and labelling.
• Quality control and regulatory laboratories performing standardized comparison of ovine and caprine rennets.
• Research institutions studying enzyme activity, cheesemaking performance, or developing new coagulants.

Related standards

• ISO 11815 / IDF 157 - Relative milk‑clotting activity test (REMCAT) for bovine rennets (method compatibility).
• IDF 110B - Determination of chymosin and bovine pepsin contents (chromatographic method).
• Laboratory glassware and equipment standards referenced (e.g., ISO 648, ISO 1042) for pipettes and volumetric flasks.

Keywords: ISO 23058:2006, ovine rennet, caprine rennet, milk‑clotting activity, IMCU, calcium chloride, rennet paste, chymosin, pepsin, REMCAT, cheesemaking.