Overview
SIST ISO 5566:1997 - Turmeric: Determination of Colouring Power by Spectrophotometric Method establishes a standardized procedure for assessing the colouring power of turmeric using spectrophotometric analysis. This international standard, adopted by SIST, focuses on the quantification of curcumin content - the primary pigment responsible for turmeric's characteristic color. The method consists of extracting pigments from ground turmeric with hot ethanol, diluting the extract, and measuring the maximum absorbance at a specific wavelength (425 nm). The final result is expressed as curcumin percentage by mass.
By using this validated method, laboratories, food manufacturers, regulators, and quality control departments can reliably compare samples and ensure product consistency.
Key Topics
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Scope of the Method: The standard outlines a uniform spectrophotometric procedure for determining turmeric’s colouring strength, ensuring quality and comparability in the spice industry.
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Analytical Principle: Ground turmeric is extracted with hot ethanol, followed by dilution and measurement at the wavelength of maximum absorption (425 nm), which is optimal for quantifying curcumin.
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Result Expression: The colouring power is calculated and reported as the percentage of curcumin by mass, providing a key quality parameter for both raw and processed turmeric.
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Required Equipment and Reagents:
- Spectrophotometer capable of measurements at 425 nm
- Matched spectrophotometric cells (1 cm optical path length)
- Reflux condenser extraction apparatus
- Analytical balance (high-precision)
- 96% ethanol as solvent
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Sampling and Preparation: The standard references ISO 948 for sampling and ISO 2825 for sample preparation, ensuring representative and finely ground samples for testing.
Applications
SIST ISO 5566:1997 has practical applications across several sectors, making it a cornerstone in turmeric quality control:
- Food Industry: Assures manufacturers that turmeric meets coloring specifications for spices, seasonings, and processed foods. This is especially relevant for brands where color strength impacts consumer acceptance.
- Quality Assurance Laboratories: Enables precise, reproducible quantification of curcumin, supporting product labelling, authenticity checks, and specification compliance.
- Regulatory Compliance: Supports governmental or third-party verification that turmeric and turmeric-based products meet internationally recognized quality standards.
- Research and Development: Facilitates scientific studies into turmeric's pigment composition, extraction efficiency, and pigment stability.
- Trade and Procurement: Allows for reliable comparison of raw materials, helping buyers and traders set prices based on pigment content and quality.
Adopting this standardized method ensures data comparability, increases confidence in test results, and improves decision-making in industrial, commercial, and regulatory environments.
Related Standards
For a complete approach to spice analysis and quality assurance, the following international standards are relevant:
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ISO 948: Spices and condiments - Sampling
Details procedures for obtaining representative samples from batches.
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ISO 2825: Spices and condiments - Preparation of a ground sample for analysis
Defines methods for preparing spices in a ground form suitable for laboratory analysis.
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ISO/TC 34: Agricultural food products
Covers a wide range of food product standards, relevant for those involved in food safety and quality.
These related standards help ensure that the assessment of turmeric’s colouring power is rigorous, repeatable, and based on internationally accepted practices.
By following SIST ISO 5566:1997, organizations benefit from standardized turmeric analysis - safeguarding quality, consistency, and trust in the global spice market.