ISO 8968-1-2014 PDF

Full title and description

ISO 8968-1:2014 — Milk and milk products — Determination of nitrogen content — Part 1: Kjeldahl principle and crude protein calculation. This International Standard specifies Kjeldahl-based procedures (traditional and block digestion) for determining nitrogen content and calculating crude protein in a wide range of milk and milk products.

Abstract

ISO 8968-1|IDF 20-1:2014 specifies a method for the determination of the nitrogen content and crude protein calculation of milk and milk products by the Kjeldahl principle, using traditional and block digestion methods. It is applicable to liquid cow, goat and sheep milk (whole, partially skimmed or skimmed), many cheeses (hard, semi-hard and processed), dried milk and dried milk products (including milk-based infant formulae, milk protein concentrate, whey protein concentrate, casein and caseinate). The methods are not applicable to samples containing ammonium caseinate.

General information

• Status: Published (confirmed).
• Publication date: 3 February 2014 (Edition 2, 2014-02).
• Publisher: International Organization for Standardization (ISO); published jointly as IDF 20-1:2014.
• ICS / categories: 67.100.10 (Milk and processed milk products).
• Edition / version: Edition 2 (2014).
• Number of pages: 18.

Key bibliographic and lifecycle details (status, publication date, edition, page count and confirmation history) are recorded by ISO; the publication was published 3 February 2014 and was last reviewed and confirmed in 2022, so the 2014 edition remains current.

Scope

Specifies Kjeldahl-based laboratory procedures (conventional and block-digestion approaches) to determine total nitrogen and to calculate crude protein for a broad set of milk and milk-derived products — including liquid milks, many cheeses and dried milk powders and concentrates. The standard explicitly excludes samples containing ammonium caseinate. The methods are intended for routine and reference-type determinations where Kjeldahl-based protein estimation is appropriate.

Key topics and requirements

• Principle: determination of nitrogen by the Kjeldahl principle and calculation of crude protein from measured nitrogen.
• Applicability: liquid milks (cow, goat, sheep), hard/semi-hard/processed cheeses, dried milk products, infant formula based on milk, milk protein and whey concentrates, casein/caseinate (except ammonium caseinate).
• Digestion methods: describes both traditional Kjeldahl digestion and block-digestion procedures suitable for routine laboratory throughput.
• Calculation: specifies conversion of measured nitrogen to crude protein using the appropriate conversion factor and reporting conventions.
• Sampling and sample preparation: guidance on representative test portions and pretreatment appropriate for milk and milk products (as relevant to Kjeldahl analysis).
• Precision and performance: sets out expected repeatability/reproducibility considerations and requirements for blank and recovery checks (general performance expectations for Kjeldahl methods).
• Limitations: notes matrices or additives (e.g., ammonium caseinate) for which the method is not suitable.

These topics summarize the core technical content; consult the full text of the standard for procedural details, reagent and apparatus specifications, safety precautions and calculation formulas.

Typical use and users

Used by food and dairy testing laboratories, quality-control teams in dairy production, regulatory and inspection bodies, research laboratories and standards organizations for routine and comparative determination of crude protein in milk and milk products. Laboratories employ this standard when Kjeldahl-based protein estimation is required for product labelling, specification control, compliance testing or research.

Related standards

ISO 8968 is a multi-part series. Relevant related publications include ISO 8968-2 (block-digestion macro method — earlier edition, subsequently superseded by the revisions consolidated in the 2014 update), ISO 8968-3 (semi-micro block-digestion routine method) and ISO 8968-4 (reference methods for protein/non-protein nitrogen and true protein calculation). For authoritative status and details of each part consult the corresponding ISO entries.

Keywords

milk; milk products; nitrogen content; Kjeldahl; crude protein; protein calculation; digestion; block digestion; dairy analysis; IDF 20-1.

FAQ

Q: What is this standard?

A: ISO 8968-1:2014 is the second-edition International Standard that defines Kjeldahl-based methods and the calculation of crude protein for milk and many milk products.

Q: What does it cover?

A: It covers the Kjeldahl principle applied to milk and milk products, detailing digestion approaches (traditional and block), calculation of crude protein from measured nitrogen and the range of applicable product types; it excludes samples containing ammonium caseinate.

Q: Who typically uses it?

A: Dairy industry QC laboratories, independent food-testing laboratories, regulatory agencies and researchers performing nitrogen/protein determinations on milk and milk-derived products.

Q: Is it current or superseded?

A: The 2014 edition (Edition 2) is published and — according to ISO — it was last reviewed and confirmed in 2022, so the 2014 edition remains the current edition. Users should verify with their national standards body or ISO store for any updates after 2022.

Q: Is it part of a series?

A: Yes — ISO 8968 is a series of parts dealing with nitrogen/protein determination in milk (e.g., Parts 1, 2, 3 and 4). Part 1 covers Kjeldahl principle and crude protein calculation; other parts cover block-digestion variants, semi-micro routine methods and reference methods for true protein/non-protein nitrogen.

Q: What are the key keywords?

A: milk, milk products, Kjeldahl, nitrogen, crude protein, protein calculation, digestion, dairy analysis.