Overview
ISO 762:2003 specifies a laboratory method for determination of mineral impurities (soil-derived impurities) in fruit and vegetable products. The standard defines a procedure to separate organic material by flotation, recover mineral sediments by sedimentation and washing, and quantify the mineral residue after incineration. ISO 762 is intended for food quality control, regulatory testing and research where assessment of mineral/soil contamination levels is required.
Key Topics and Requirements
- Scope and principle: Separation of organic matter by flotation, sedimentation of mineral impurities, incineration of the sediment and weighing of the residue.
- Sample preparation: Mix whole laboratory sample; for dried products rehydrate 20 g in ~400 ml water overnight. Typical test portion is 100 g (or entire smaller sample).
- Apparatus: Blender, 1 000 ml beakers, Whatman No. 41 (or equivalent) filter paper, incineration dishes (quartz/porcelain/platinum), muffle furnace (525 °C ± 25 °C), desiccator, analytical balance (capable of 0.0002 g), heater, sieve (≈1–2 mm), washing equipment.
- Washing procedure: Use a water tank with leak tube and glass tube(s) to wash suspension. Specified flow conditions produce ~200 ml/min through a glass tube; immerse tip 6 cm from beaker bottom and wash for 35–40 minutes to remove fine plant fragments.
- Incineration and weighing: Heat filter paper + residue, incinerate at ~525 °C for 1 hour, cool in desiccator and weigh to constant mass.
- Calculation: Mineral impurities (%) = 100 × (m1 − m0) / m
where m = test portion mass, m0 = empty dish mass, m1 = dish + incinerated residue mass.
- Quality criteria: At least two determinations required. Repeatability: the absolute difference between two results will in not more than 5% of cases be greater than 3% of the mean value.
- Reporting: Include sample identification, sampling method, reference to ISO 762, any deviations/operating details and the result to two decimal places.
Applications and Users
ISO 762 is used by:
- Food testing laboratories conducting quality control on fruits, vegetables and derived products.
- Food manufacturers monitoring soil/mineral contamination during processing and cleaning operations.
- Regulatory agencies enforcing cleanliness and safety standards for fruit and vegetable products.
- Research groups studying contamination sources, washing efficiency, and post-harvest handling.
Keywords: ISO 762, mineral impurities, fruit and vegetable products, soil contamination, laboratory method, incineration, sedimentation.
Related Standards
- Prepared by ISO/TC 34 (Food products), Subcommittee SC 3 (Fruit and vegetable products). For broader context, consult other ISO standards on sampling, microbiological testing and chemical analysis of foodstuffs (refer to ISO catalogues for specific references).