• QA 201
    Does air quality affect green coffee beans?
    I am looking for information on air quality standards at the point of sun drying coffee parchment (or if not available that specifically, at any point along the transformation of the coffee, excluding roasting stage). If not available, then I am looking for any work on how taints are transferred to coffee beans and any mitigation measures to be taken.
    Asked by:
    Grower - Jamaica

    Yes, air quality can affect coffee quality in the sense that green beans readily take up taints and off-flavours. Just as they absorb moisture. Airborne smells and odours can affect coffee during processing and storage, particularly if these are strong/pungent, or if the moisture content of the green bean is too high.

    We are not aware of any published 'standards' for air quality in relation to coffee processing and would suggest that in most instances simple common sense will dictate what is and is not acceptable. We say this because, usually, on-farm processing will take place in a rural environment where air quality should be good. If so then one should look at the farm environment to determine whether a potential exists for air-borne taints. Air-borne because this is your question - we assume you are well aware of the risk of taints and off-flavours developing during harvesting, wet processing and drying: clean picking baskets, clean water, general cleanliness and total discipline are essential.

    Air quality will be improved if

    • Primary processing, drying, storage and export processing are located away from

              - Composting pulp from the wet process;
              - Settling ponds for wastewater from the wet process;
              - Gravel or dirt roads that produce dust;
              - Chemical and/or fuel (diesel, petrol) stores;

    • Coffee is only stored in dedicated, clean stores and is never commingled with other goods or materials;
    • Nowhere in the processing or storage areas are there any open exhausts from diesel or petrol driven engines, including tractors and trucks;
    • The airflows that operate gravity tables and sorting equipment are absolutely free from oil taints and engine-driven compressors are outside the building;
    • Air used in artificial drying is carefully filtered to exclude any fuel odour;
    • The entire processing and storage area is kept meticulously clean and is inspected on a regular basis, if not daily;
    • Smoking and food consumption are prohibited in processing and storage areas;

    Your question is very pertinent because, as said, coffee readily takes up taints and off-flavours. For example possible contamination from some types of jute bags - see topic 12.07 of the Guide for more on this. It is also important to ensure that trucks and containers used for transport are inspected on smells and cleanliness before loading, and that drivers are prohibited from picking up passengers and their luggage en route.

    These are basic preconditions for a clean environment that all staff should understand and respect - training and regular follow-up is essential. 

    For more in-depth discussion or analysis we would suggest to visit www.asic-cafe.org, the website of the Association Scientifique Internationale du Café. ASIC specialises in the collection and dissemination of coffee-science related information - however, one has to subscribe. Some interesting information on coffee storage options is also available at www.mesoamerican.org.

    Chapter 11 of the Guide deals with Coffee Quality generally whereas Chapter 12 deals with Quality Control issues.

    Posted 22 September 2008

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