ISO 1575:1987

Overview

ISO 1575:1987 is an international standard published by the International Organization for Standardization (ISO) that specifies a precise method for the determination of total ash content in tea. This method helps quantify the inorganic residue remaining after the combustion of the organic matter within tea samples. The standard aims to provide a consistent and repeatable procedure to ensure accurate quality control and characterization of tea products.

The standardized process involves incinerating a prepared tea sample at a controlled temperature of 525 ± 25 degrees Celsius until the mass reaches a constant value. This destructive analysis removes all organic material, leaving only mineral ash for measurement. ISO 1575:1987 ensures that laboratory results are comparable globally by detailing sample preparation, apparatus, and calculation formulae.

Key Topics

• Scope and Application: Applies to the quantitative determination of total ash in tea, contributing to quality assessment and regulatory compliance.
• Sample Preparation: Requires use of a tea sample ground to a known dry matter content, in accordance with ISO 1572.
• Apparatus Requirements:
  • Capsules (50-100 ml) made of platinum, porcelain, or other inert materials (silica capsules are unsuitable).
  • Temperature-controlled furnace able to maintain 525 ± 25 °C.
  • Analytical balance with precision to 0.001 g.
  • Dessicator with effective drying agent.
  • Hot water bath and heating plate to dry samples between steps.
• Test Procedure:
  • Preheat capsule to constant mass.
  • Weigh approximately 5 g of prepared sample in capsule.
  • Heat initially near 100 °C to remove moisture.
  • Incinerate at 525 ± 25 °C until ashes show no black residue (typically minimum 2 hours).
  • Hydrate, dry, and reheat the ash to remove soluble impurities.
  • Repeat heating and weighing until mass stabilization within 0.001 g.
• Calculation: Total ash content expressed as a percentage of the dry sample mass using a defined formula.
• Quality Control: Duplicate determinations with a specified repeatability limit (maximum 0.2 g difference for 100 g sample).
• Documentation: Test reports must detail the method used, any deviations, sample identification, and test results.

Applications

The ISO 1575:1987 method is critical for:

• Quality Assurance in Tea Production: Helps producers assess mineral residue levels, which can affect flavor, safety, and regulatory compliance.
• Regulatory Compliance: Supports meeting food safety standards related to inorganic content.
• Research and Development: Provides a reliable baseline for studies on tea composition, processing effects, and adulteration detection.
• Trade and Certification: Enables consistent quality benchmarks across international markets and certification bodies.
• Complementary Analysis: Can be combined with ISO 1576 (soluble and insoluble ash) or ISO 1577 (acid-insoluble ash) for detailed inorganic profiling.

Related Standards

• ISO 1572: Specifies the preparation of tea samples with known dry matter content, essential for accurate ash testing.
• ISO 1576: Details methods for determination of water-soluble and insoluble ash components in tea.
• ISO 1577: Describes the determination of acid-insoluble ash in tea, useful for detecting soil or sand contamination.

ISO 1575:1987 fits within the broader framework of agricultural food product standards under ISO/TC 34, ensuring that tea analysis methods remain harmonized and scientifically robust.

Keywords: ISO 1575, tea total ash determination, tea quality control, inorganic residue analysis, tea testing standards, tea ash content, sample incineration method, ISO tea standards