ISO 6668:2008

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.