Overview
ISO 6668:2008 - "Green coffee - Preparation of samples for use in sensory analysis" defines a standardized procedure for preparing green coffee samples for sensory testing. The standard covers roasting, cooling, grinding and brewing a beverage from roast-and-ground coffee so that sensory analysis (cupping) is repeatable and suitable for quality control, comparative assessment and acceptance/rejection of shipments (by agreement).
Key Topics and Requirements
- Roasting
- Batch roaster: 100–300 g sample; drum roasts typically 5–12 min.
- Bean temperature guidance: generally 200 °C–240 °C.
- Roast level: light roast for defect detection; medium roast for flavour and colour assessment.
- Rapid cooling to ~30 °C within 5 minutes using forced air through a perforated plate.
- Grinding
- Laboratory grinder capable of ~100 g in ≤1 min.
- Target particle size distribution (mass fractions):
- Retained on 600 µm sieve ~70% (min 60%, max 75%)
- Retained on 425 µm sieve ~20%
- Through 425 µm ~10% (min 5%, max 15%)
- Perform a test sieving at start of each working day.
- Beverage preparation (infusion)
- Water: meet ISO 3696 grade 3; medium hardness; CaCO3 up to 2.5 mmol/L (dilute if exceeded).
- Coffee-to-water ratio: preferred 7.0 g per 100 ml (acceptable range 5–9 g unless agreed otherwise).
- Use clean, odour-free cups (150–350 ml). Pour freshly boiled water, allow infusion to stand ~3 minutes, stir gently, skim surface grounds and cool to ≤55 °C. First tasting typically at 50–55 °C.
- Equipment & reporting
- Specified apparatus: batch roaster, thermometer, balance (0.1 g), laboratory grinder, sieves (ISO 565), cups, heating device.
- Test report must include sample ID, method reference, roasting temperature/time and any deviations or incidents.
Applications and Who Uses It
- Practical uses
- Standardized cupping for quality control, comparative evaluations and contractual acceptance/rejection of coffee lots.
- Ensures consistent sample handling across labs and between trading partners for reliable sensory results.
- Primary users
- Coffee quality/control laboratories, roasteries, green coffee buyers and exporters, sensory panels, research institutions and certification bodies.
Related Standards
- ISO 3696 - Water for analytical laboratory use
- ISO 565 - Test sieves (nominal openings)
- ISO 4072 - Green coffee in bags - Sampling
Keywords: ISO 6668:2008, green coffee, sensory analysis, sample preparation, roasting, grinding, coffee quality control, cupping, beverage preparation.
