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  • 11.5.6-COFFEE QUALITY-APPEARANCE - AVOID OBVIOUS DEFECTS

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  • Appearance - avoid obvious defects

     
     
    Coffees containing black beans, obvious stinkers, water-damaged beans and foreign matter stand no chance, not only in the quality market but also not for the great majority of roasters. This should be obvious to anyone in the coffee business, so what follows is limited to the perhaps not so well recognized appearance (green) defects that put off quality buyers and cause them to reject one coffee in favour of another. This explains why seemingly good samples are rejected or why some buyers simply do not respond to them at all.

    Coated.The silver-skin has adhered to more than half a bean's surface. The immediate consequence is that the green appearance suffers because the silver-skin obscures the bean's surface and true colour. Too much coatedness does not look good. The roaster also knows that the silver-skin tends to burn off during roasting and the resultant chaff can pose problems.

    Coated beans are caused by drought and by trees over-bearing. Both of these tend to affect the cherry in similar ways, and the coffee's style and general aspect are usually not impressive. General coatedness can also result from under-fermentation. Beans that are entirely coated may originate from unripe cherry. Coffees with pronounced coatedness often produce common, ordinary liquors. The experienced coffee buyer will tend to instinctively discriminate against such coffees, also because the roast will usually contain ragged, soft and sometimes pale beans.

    If possible one should not mix coffee from drought-affected trees with that of others. However, many coated beans will lose their silver-skin during hulling (or polishing, where this is installed). Very coated beans are usually also ragged and smaller or lighter than the norm and may be removed during grading and sorting.

    Before rushing into polishing to remove the silver-skin, first establish whether the coatedness of your coffee is a problem and, if so, what the cause might be. Polishing as such adds nothing to coffee quality but does improve the colour and overall appearance (unless the polisher has excessively heated the beans, which has the opposite effect). Correct (i.e. cool) polishing may make a coffee more easily saleable. Some robustas are polished as a matter of course, but for arabica it is advisable to first verify whether polishing makes commercial sense.

    Ragged or uneven. Ragged refers to drought-affected and misshapen beans that give the green an uneven aspect. Too many ragged beans in a coffee suggest less than optimal quality, neither green nor roast are pleasing to the eye and such coffee is not usually suitable for sale as whole roasted bean. Ragged coffees often produce mediocre liquors - but one cannot generalize because some sought-after original coffees show beans with naturally meandering centre cuts as a matter of course. Great care must be taken therefore to distinguish between the visual or cosmetic aspects of different coffees and the quality.

    An uneven green can also be the result of mixing different coffees, for example a roundish bean (Bourbon) with a flattish bean (Typica), or a boat-shaped (Ethiopian) variety. Where possible it is probably best to leave decisions on the mixing of different cultivars and types to the buyer.

    The fundamental causes of raggedness can be addressed only in the field. All processing can do is: separate light and heavy cherry before pulping (by grading or flotation: smallholders can even do this using a simple bucket or basin); systematic washing and grading after pulping; and intensive size and especially density separation during dry (export) processing. The most useful tool in this respect is without any doubt the gravity table (table densimetrique in French). Properly set and supervised, this machine will eliminate many if not most ragged beans.

    Pulper-nipped beans are the result of incorrectly set pulpers. They are very difficult to remove during export grading and sorting. If those beans are also discoloured they can also cause fermented, foul or unclean cups as described in the next paragraph. Experienced buyers will notice pulper-nipped beans and the risk message they convey.