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AS ISO 8968.4:2021
$109.95
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)
Identically adopts ISO 8968 4:2016, which specifies a method for the direct and indirect determination of the protein nitrogen content of liquid, whole or skimmed milk. KEYWORDS: Milk; Nitrogen; Protein content
Table of contents
Header
About this publication
Preface
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
6.1
6.2
6.3
6.4
6.5
6.6
6.7
7 Sampling
8 Preparation of test sample
9 Procedure — Direct protein nitrogen approach
9.1 Test portion
9.2 Determination
9.2.1 Precipitation and filtration
9.2.2 Preparation of the precipitate
9.2.3 Digestion and distillation
9.2.4 Titration
9.3 Blank test
9.4 Calculation and expression of results
9.4.1 Calculation of protein nitrogen content
9.4.2 Expression of results
9.4.3 Calculation of true protein content
9.4.4 Expression of the true protein content results
10 Procedure — Indirect protein nitrogen approach
10.1 Nitrogen determination
10.2 Non-protein nitrogen determination
10.2.1 Test portion
10.2.2 Precipitation and filtration
10.2.3 Preparation of the filtrate
10.2.4 Digestion and distillation
10.2.5 Titration
10.3 Blank test
10.4 Calculation and expression of results
10.4.1 Calculation of non-protein nitrogen content
10.4.2 Calculation of protein nitrogen content
10.4.3 Expression of results
10.4.4 Calculation of true protein content
10.4.5 Expression of the true protein content results
