Overview
ISO 763:2003, "Fruit and vegetable products - Determination of ash insoluble in hydrochloric acid," specifies an analytical method to measure the hydrochloric‑acid‑insoluble ash in fruit and vegetable products. The procedure detects siliceous impurities together with the plant’s endogenous silica, providing a standardized way to quantify sand, soil-derived minerals and silica residues in food matrices.
Key topics and requirements
- Scope: Quantification of HCl‑insoluble ash (siliceous impurities and plant silica) in fruit and vegetable products.
- Principle: Incinerate a representative test portion and separate the fraction insoluble in dilute hydrochloric acid.
- Reagents: 10% (m/m) hydrochloric acid; silver nitrate solution for chloride testing; analytical‑grade reagents and deionized water.
- Apparatus: blender for sample homogenization, muffle furnace (525 °C ± 25 °C), drying oven (103 °C ± 2 °C), boiling water bath, quartz or platinum incineration dishes, ashless filter paper, and an analytical balance with 0.0002 g readability.
- Procedure highlights:
- Prepare a representative test sample (thaw and include purge liquid for frozen samples).
- Dry (if needed), carbonize and incinerate sample at ~525 °C.
- Treat ash with 10% HCl, filter, wash until no chloride remains (checked with AgNO3).
- Dry and re‑incinerate residue, cool in a desiccator and weigh to constant mass.
- Results: Expressed as percentage by mass (or g/100 ml for liquids). Report to two decimal places.
- Repeatability: Difference between two single tests will exceed 0.01 g of HCl‑insoluble ash per 100 g in no more than 5% of cases.
Applications and users
ISO 763:2003 is used for quality control, regulatory compliance and contamination screening in the food industry. Typical users include:
- Food testing laboratories conducting compositional and contaminant analyses
- Fruit and vegetable processors monitoring product cleanliness
- Regulatory and inspection agencies checking adherence to food standards
- Certification bodies and researchers studying mineral contaminants and silica content
Practical uses include detection of soil/sand contamination, verifying cleaning and handling processes, and providing data for product specifications or regulatory reporting.
Related standards
- ISO 762 - Fruit and vegetable products - Determination of mineral impurities content (referenced for broader mineral impurity testing).
Keywords: ISO 763:2003, ash insoluble in hydrochloric acid, fruit and vegetable products, siliceous impurities, HCl‑insoluble ash, food testing, muffle furnace, incineration method, analytical standard.
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