• QA 060
    Would exporters of gourmet coffee benefit from sorting equipment that detects phenolic beans and other bacteria that affect the cup, but do not impact the green color of the bean?
    We manufacture an electronic sorting machine that detects phenolic beans and other bacteria that affect the cup, but doesn't impact the green color of the bean. How important could this technology be for gourmet coffee exporters?
    Asked by:
    Manufacturer - United States

    Strictly speaking your question does not fall within our scope of coverage. However, the question of why beans of good green appearance nevertheless sometimes produce off-tastes has always been of interest because such beans can cause unexpected problems for roasters. This is particularly so for gourmet/specialty roasters who normally roast smallish batches that offer little chance of the offending bean being dispersed over a large quantity. Such chemically altered beans include phenolic beans, 'invisible stinkers', beans producing potato flavour or peasiness, and possibly others.

    Already in June 1975 at the 7th International Scientific Colloquium on Coffee in Hamburg, the East African Industrial Research Organization in Nairobi presented a paper dealing with the identification of over-fermented beans (stinkers) through exposure to ultra-violet light that made such beans fluoresce because their chemical composition was different from that of sound beans. Yet such beans were often unrecognizable with the naked eye: an important finding.

    To note though that as coffee ages so its chemical composition changes as well: the resultant woody or old taste is in fact the result of chemical change.And this means that as the beans age, so most or all of them begin to fluoresce. This then makes it impossible to select the offending beans that were the original target. Therefore, as we understand it, for the ultra-violet sorting process to work well it should only be used for fresh coffee, promptly after milling. Also, the coffee should not be overly coated, i.e. not too much silver skin is still attached to the beans. Within these limitations we estimate that for certain producers UV sorting equipment may be of interest and we would refer interested readers to visit www.satake-usa.com to obtain further information or contact vision@satake-usa.com to enquire about UV sorting equipment.

    Posted 24 November 2005

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