Overview
ISO 6667:1985 - "Green coffee - Determination of proportion of insect-damaged beans" defines a standardized, practical method for assessing insect damage visible on the external surface of green (unroasted) coffee beans. The method uses visual examination to count insect-damaged beans in a test portion, estimate the observed percentage damaged, and - where possible - identify the insect species responsible. Statistical tools provided in the standard allow estimation of confidence limits and the probability that the true proportion in the lot does not exceed a chosen threshold.
Key topics and requirements
- Scope: Applies to external, visually detectable insect damage on green coffee (see ISO 3599 definition).
- Inspection principle: Visual examination of whole beans; only clear insect holes/cavities that cannot be mistaken for other damage are counted as “insect-damaged.”
- Apparatus: Magnifying glass recommended (×5); optional sample-holder to facilitate counting.
- Sampling and test portion:
- Randomly select at least 100 whole green coffee beans from the laboratory sample (see ISO 4072 for sampling).
- Replace broken beans during counting with random whole beans from the test sample.
- Identification of common pests:
- Hypothenemus (Stephanoderes) hampei (coffee bean borer): small, neat circular entry/exit holes ~0.3–1.5 mm; often with blue‑green stain.
- Araecerus fasciculatus (coffee bean weevil): larger bored holes ~1.0–3.0 mm, less neat.
- Verification: Use a pin to distinguish surface stains from actual cavities when needed.
- Statistical interpretation:
- Calculate the observed proportion (%) = (number of damaged beans / total beans examined) × 100.
- Use provided figures to determine confidence limits (e.g., 90% probability suggested) and the probability that the true lot proportion does not exceed a given value.
- Option to combine two test portions (second portion ≥ 200 beans) to reduce confidence intervals.
- Annexes:
- Annex A: photographic illustrations of damage types.
- Annex B: statistical test for homogeneity of the laboratory sample (90% or 95% significance thresholds).
Practical applications and users
ISO 6667:1985 is used by:
- Coffee quality control laboratories and inspectors
- Exporters, importers and commodity traders for acceptance/arbitration testing
- Roasters and procurement teams assessing green coffee lots
- Regulatory agencies and certification bodies monitoring pest damage
The standard supports consistent assessment of insect-damaged beans for commercial decisions, technical quality control, and dispute resolution.
Related standards
- ISO 3599 - Definition of green coffee
- ISO 4072 - Green coffee in bags - Sampling
- ISO 3509 - Coffee and its products - Vocabulary
Keywords: ISO 6667:1985, green coffee, insect-damaged beans, coffee bean borer, coffee bean weevil, visual examination, sampling, confidence limits, homogeneity test.