Milk and milk products. Determination of nitrogen content. Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method) (ISO 8968-4:2016)
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ISO 8968-4|IDF 20-4:2016 specifies a method for the direct and indirect determination of the protein nitrogen content of liquid, whole or skimmed milk.
Tämän julkaisun valmistelusta Suomessa vastaa SFS Suomen Standardit, puh. 09 149 9331.
Sisällysluettelo
Forewords
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
4.1 Indirect protein nitrogen
4.2 Direct protein nitrogen
5 Reagents
5.1 General
5.2 Trichloroacetic acid (CCl3COOH) solution
5.3 Hydrochloric acid standard volumetric solution
6 Apparatus
7 Sampling
8 Preparation of test sample
9 Procedure — Direct protein nitrogen approach
9.1 Test portion
9.2 Determination
9.3 Blank test
9.4 Calculation and expression of results
10 Procedure — Indirect protein nitrogen approach
10.1 Nitrogen determination
10.2 Non-protein nitrogen determination
10.3 Blank test
10.4 Calculation and expression of results
11 Precision
11.1 Interlaboratory test
11.2 Repeatability
11.3 Reproducibility
12 Test report
Annex A Results of a collaborative study — Estimation of precision data of direct and indirect methods for the true protein determination (informative)
5.3 Hydrochloric acid standard volumetric solution
6 Apparatus
7 Sampling
8 Preparation of test sample
9 Procedure — Direct protein nitrogen approach
9.1 Test portion
9.2 Determination
9.3 Blank test
9.4 Calculation and expression of results
10 Procedure — Indirect protein nitrogen approach
10.1 Nitrogen determination
10.2 Non-protein nitrogen determination
10.3 Blank test
10.4 Calculation and expression of results
11 Precision
11.1 Interlaboratory test
11.2 Repeatability
11.3 Reproducibility
12 Test report
Annex A Results of a collaborative study — Estimation of precision data of direct and indirect methods for the true protein determination (informative)