ISO 1578:1975

Overview

ISO 1578:1975 specifies a standardized method for determining the alkalinity of water-soluble ash in tea. This international standard, published by the International Organization for Standardization (ISO), outlines a precise titration procedure using a standard hydrochloric acid solution and methyl orange as an indicator. The method ensures consistency and reliability in chemical analysis related to tea quality and composition, vital for agricultural, food safety, and analytical laboratories worldwide.

Key Topics

• Scope: The standard applies to the titration of filtrate obtained from water-soluble ash of tea, determining its alkalinity quantitatively.
• Chemical Principle: The alkalinity is measured by titrating the aqueous extract of total ash with 0.1 N hydrochloric acid, using methyl orange to indicate the endpoint.
• Sample Preparation: Analytical testing involves two replicates of the filtrate from water-soluble ash determination to ensure accuracy.
• Calculation: Results are expressed either as milliequivalents of acid required per 100 g of the dry ground tea sample or as a percentage by mass of potassium hydroxide (KOH).
• Reagents and Equipment: The standard specifies the use of 0.1 N hydrochloric acid and methyl orange indicator solution.
• Reporting: Detailed reporting guidelines ensure clear communication of methods, conditions, and results.

Applications

ISO 1578:1975 is essential in various practical contexts:

• Tea Quality Control: Monitoring alkalinity helps in assessing the tea's chemical properties, which influence taste, processing, and consumer health.
• Agricultural Product Testing: Ensures that tea products meet established compositional standards across different production batches.
• Laboratory Standardization: Provides a universally accepted procedure for laboratories engaged in tea analysis, improving reproducibility and comparability of results internationally.
• Regulatory Compliance: Assists regulatory bodies and manufacturers in validating product compliance with quality and safety standards.
• Research and Development: Supports scientific studies focusing on tea chemistry, processing effects, and quality enhancement.

Related Standards

ISO 1578:1975 is closely linked with other ISO standards that collectively support comprehensive tea analysis:

• ISO 1572: Tea - Preparation of Ground Sample of Known Dry Matter Content: Defines the preparation method ensuring accurate dry basis measurements.
• ISO 1575: Tea - Determination of Total Ash: Provides procedures for total ash content determination relevant for initial sample analysis.
• ISO 1576: Tea - Determination of Water-Soluble Ash and Water-Insoluble Ash: Directly connected as ISO 1578 uses the filtrate from this standard’s procedure.

By following ISO 1578:1975, laboratories benefit from a trusted, validated method for determining water-soluble ash alkalinity, contributing to consistent global standards in tea analysis and quality assurance.