Overview
EN ISO 8968-1:2014 (ISO 8968-1:2014 / IDF 20-1:2014) specifies a standardized laboratory method for determining nitrogen content and calculating crude protein in milk and milk products using the Kjeldahl principle. The standard covers both traditional and block digestion approaches and applies to cow, goat and sheep whole milks, hard/semi‑hard/processed cheeses, and a wide range of dried milk products (including infant formula, milk protein concentrate, whey protein concentrate, casein and caseinate). The method is not applicable to products containing ammonium caseinate.
Key topics and technical requirements
- Analytical principle: Conversion of organic nitrogen to ammonium by acid digestion (Kjeldahl), followed by quantitation to calculate crude protein as a percentage.
- Digestion methods: Acceptance of both traditional digestion and modern block digestion systems; use of appropriate catalysts and reagents is specified.
- Reagents noted: Concentrated sulfuric acid and potassium sulfate for digestion; copper sulfate (II) used as a catalyst (as described in the standard).
- Sample types & preparation: Procedures for liquid milks, cheeses and dried milk products; provisions for sampling and test portion preparation.
- Quality controls: Blank tests, recovery tests and precision data from collaborative (interlaboratory) trials are included to support result validity.
- Safety and conformity: The standard contains warnings about hazardous materials and recommends appropriate laboratory safety practices.
- Normative references: Includes laboratory glassware and volumetric apparatus standards (e.g., ISO 385, ISO 8655-3) and supersedes earlier editions (EN ISO 8968-1:2001 and EN ISO 8968-2:2001).
Applications and who uses it
- Dairy laboratories performing routine composition testing and nutritional labeling (crude protein reporting).
- Quality control teams in dairy processing plants monitoring product formulation and consistency.
- Regulatory and conformity bodies assessing compliance with food labeling and compositional requirements.
- Ingredient manufacturers (milk powders, protein concentrates) and R&D groups validating protein content for formulation and claims.
- Third‑party testing laboratories providing accredited testing services (ISO/IEC 17025) for dairy products.
Related standards
- EN ISO 8968-2 (other parts of the series) and earlier versions superseded by this edition.
- Normative references such as ISO 385 (burettes) and ISO 8655-3 (piston burettes) for volumetric apparatus.
EN ISO 8968-1:2014 is central for reliable, comparable determination of milk nitrogen and crude protein-essential for product labeling, regulatory compliance, and quality assurance in the dairy sector. Keywords: EN ISO 8968-1:2014, ISO 8968-1, Kjeldahl, crude protein, milk nitrogen determination, dairy testing standard.
