Overview
EN ISO 14673-3:2004 is a standardized method developed by CEN and ISO for the determination of nitrate and nitrite contents in milk and milk products. This routine analytical procedure employs cadmium reduction combined with flow injection analysis (FIA) with in-line dialysis, enabling precise detection and quantification of these compounds in diverse dairy matrices. The method applies to a wide range of cheeses-hard, semi-hard, soft, and processed varieties-as well as whey powder, milk powder, and milk-based infant food.
The standard defines detection limits at 0.5 mg/kg for nitrate ions and 1.0 mg/kg for nitrite ions, reflecting high sensitivity suitable for routine dairy quality control and safety assessment.
Key Topics
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Scope and Applicability
The standard covers nitrate and nitrite analysis in milk, cheese (various firmness and aging stages), processed cheese, and powdered dairy products including infant formulas.
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Principle of the Method
The procedure involves suspending a test sample in an extraction buffer, separating fat via centrifugation and cooling, then analyzing the defatted solution. Flow injection analysis with in-line dialysis is used to remove proteins and residual fats prior to measurement.
Nitrates are reduced to nitrites by passing through a cadmium column. Subsequently, nitrites react with sulfanilamide and N-1-naphthyl ethylenediamine dihydrochloride, forming a red azo dye. Absorbance is measured spectrophotometrically at 540 nm with reference at 620 nm to quantify nitrate and nitrite concentrations.
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Detection Limits
- Nitrate: 0.5 mg/kg
- Nitrite: 1.0 mg/kg
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Key Reagents and Equipment
- Cadmium reduction column for nitrate to nitrite transformation
- Extraction buffer based on ammonium chloride, adjusted to pH 8.5 with ammonia
- Sulfanilamide and N-1-naphthyl ethylenediamine dihydrochloride for colorimetric detection
- Flow injection analysis apparatus with in-line dialysis
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Calculation and Correction
If nitrite exceeds 0.5 mg/kg or 10% of nitrate content, nitrate values are corrected by subtracting nitrite content for accurate quantitation.
Applications
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Dairy Industry Quality Control
EN ISO 14673-3:2004 is vital for routine monitoring of nitrate and nitrite levels in various dairy products, ensuring compliance with regulatory safety limits and maintaining product quality.
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Food Safety Analysis
Detecting nitrate and nitrite compounds helps prevent potential health risks associated with these additives or contaminants, especially in infant foods and processed cheese.
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Research and Development
Enables detailed study of nitrate/nitrite presence and transformations during dairy product processing and aging.
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Regulatory Compliance
Laboratories analyzing dairy products in Europe and internationally can rely on this standardized method to produce consistent and comparable results adhering to ISO and CEN quality standards.
Related Standards
- EN ISO 14673-1:2004 – Method using cadmium reduction and spectrometry for nitrate and nitrite determination.
- EN ISO 14673-2:2004 – Method using segmented flow analysis (SFA) as an alternative routine method.
- ISO 1042 – Specifications for laboratory volumetric glassware essential for accurate reagent preparation.
- General ISO/IDF standards on milk and milk products sampling and analytical procedures.
Summary
EN ISO 14673-3:2004 provides the dairy sector with a robust, sensitive, and routine analytical technique to measure nitrate and nitrite contents using cadmium reduction and advanced flow injection analysis with in-line dialysis. It supports product safety monitoring, compliance with food safety regulations, and quality assurance across a broad range of milk-based foods, strengthening consumer protection and industry reliability.
Keywords: nitrate determination, nitrite determination, milk products analysis, dairy standard, cadmium reduction, flow injection analysis, in-line dialysis, cheese nitrate testing, milk powder nitrate content, infant food safety
