ISO 6635:1984

Overview

ISO 6635:1984 specifies a standardized method for the determination of nitrite and nitrate content in fruits, vegetables, and derived products using a molecular absorption spectrometric method. Developed by the International Organization for Standardization (ISO), this standard is vital for food quality assessment and safety evaluation across the agricultural and food processing sectors. The procedure described ensures reliable, reproducible results, supporting compliance and comparability in international food trade and regulatory frameworks.

Key Topics

• Sample Preparation: Detailed instructions for homogenizing and preparing fruits, vegetables, and their products, including special handling for frozen samples for accurate chemical analysis.
• Extraction and Precipitation: Extraction of analytes with hot water, followed by protein precipitation using potassium hexacyanoferrate(II) and zinc acetate.
• Filtration and Color Development: Filtration removes precipitated proteins. Nitrite is directly measured, while nitrate is first reduced to nitrite using metallic cadmium.
• Spectrometric Measurement: Both nitrite and reduced nitrate are quantified by forming a red complex with sulfanilamide chloride and N-(1-naphthyl)ethylenediamine, then measuring molecular absorption at 538 nm.
• Calibration and Calculation: Utilization of standard solutions and calibration graphs for accurate quantification.
• Reporting: Results are expressed as milligrams per kilogram or liter, ensuring clarity and regulatory compliance.

Applications

The test method outlined in ISO 6635:1984 finds broad practical applications, particularly where food safety and regulatory compliance are priorities:

• Food Quality Assurance: Ensures fruit and vegetable products meet safety standards regarding nitrite and nitrate content.
• Regulatory Compliance: Supports legal limits and guidelines on nitrite and nitrate levels prescribed by national and international authorities.
• Research and Development: Used by food scientists and laboratories to evaluate the impact of agricultural practices, food processing, and storage on nitrite and nitrate concentrations.
• International Trade: Facilitates the acceptance of food products across borders by providing a recognized and reproducible method for nitrite and nitrate analysis.
• Quality Control in Processing: Employed by manufacturers and processors to monitor product consistency and safety throughout production.

Related Standards

Organizations and laboratories that use ISO 6635:1984 may also refer to related standards to complement or expand their testing and quality control procedures:

• ISO 7002 - Agricultural food products - Layout for a standard method of sampling
• ISO 750 - Determination of Titratable Acidity in Fruits and Vegetables
• ISO 2859-1 - Sampling procedures for inspection by attributes
• ISO/TC 34 - Agricultural food products technical committee standards
• Regional or national regulations on food contaminants

Conclusion

ISO 6635:1984 establishes a systematic, reliable method for determining nitrite and nitrate content in fruits, vegetables, and their derivatives using molecular absorption spectrometry. Employing this standard safeguards public health, supports international trade, and upholds food quality by enabling accurate, standardized testing practices across the global food industry. Adhering to ISO 6635:1984 is essential for laboratories, food producers, and regulatory bodies aiming to ensure product safety and compliance with food safety standards.