Overview
ISO 751:1998 is an international standard established by the International Organization for Standardization (ISO) focused on the determination of water-insoluble solids in fruit and vegetable products. This standard specifies a reliable laboratory method for measuring the content of solids that do not dissolve in water within the edible parts of these products. It is essential for quality control, product characterization, and compliance in the agricultural food processing industry.
By providing a standardized procedure, ISO 751:1998 supports manufacturers and laboratories in ensuring consistent product quality, supporting nutritional labeling, and facilitating international trade of fruit and vegetable products.
Key Topics
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Scope and Application
The standard applies to the edible parts of fruit and vegetable products with no specific limitations on product type. It covers fresh, processed, and frozen goods.
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Analytical Principle
The core principle involves dissolving water-soluble matter in a sample with water followed by filtration, drying, and weighing of the residual water-insoluble solids.
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Required Apparatus
Essential laboratory tools include beakers, Buchner funnels, filter paper of medium texture, desiccators, ovens maintaining 103°C ± 2°C, centrifuges, and high-precision analytical balances.
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Sampling and Sample Preparation
Samples must be representative and undamaged. Non-edible parts such as stalks, stones, and pips are removed prior to testing. Frozen samples are thawed, and resulting liquids are included in mixing.
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Measurement Procedure
Defined sample masses (10–100 g depending on product consistency) are mixed with distilled water, heated, filtered, washed, dried to constant weight, and weighed with precision.
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Special Cases
Product-specific conditions addressed include handling of crystallized compounds in grape juice and citrus products, processing of sweetened products requiring extended boiling, and solutions for difficult-to-filter high pectin or sugar content products, often involving centrifugation.
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Result Expression and Repeatability
Results are expressed as a percentage of water-insoluble solids by mass related to the edible portion. Repeatability criteria ensure that test results are consistent within narrow variation limits.
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Test Reporting
Reports must comprehensively document sample identification, method details, any deviations or incidents, test results, and repeatability checks for transparency and traceability.
Applications
ISO 751:1998 is widely applied to:
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Quality Control in Food Processing
Ensures consistent textural and compositional attributes in fruit and vegetable products such as juices, concentrates, jams, and preserves.
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Nutritional and Ingredient Labeling
Helps quantify insoluble solids affecting dietary fiber, texture, and product appearance for accurate labeling.
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Research and Development
Assists product formulation and process optimization by providing dependable data on insoluble solids content.
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Trade and Regulatory Compliance
Supports regulatory agencies and exporters to verify product characteristics and meet international requirements.
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Food Safety and Authenticity Testing
Identifies adulteration or improper processing through insoluble solids content analysis.
Related Standards
- ISO 6564 – Fruit and vegetable products - Determination of soluble solids content - Refractometric method
- ISO 2173 – Fruit and vegetable products - Determination of soluble solids content - Refractometric method for products with high sugar content
- ISO 1132 – Fruit and vegetable products - Determination of moisture content
These standards complement ISO 751:1998 by covering other critical parameters such as moisture and soluble solids, enabling comprehensive quality assessment of fruit and vegetable products.
By adhering to ISO 751:1998, laboratories and food industries can achieve high accuracy and reproducibility in measuring water-insoluble solids, enhancing product quality and consumer trust globally.