• Insect and pest damage

    Controlling insects and other pests can be a problem, especially in countries where coffee is grown in small patches, sometimes of a few hundred trees only and often widely dispersed and scattered over substantial areas. Such conditions make effective treatment difficult. Insect damage in the beans suggests less than optimal care of the tree park. It detracts from the coffee's visual attraction, and buyers know that insect damaged beans cause common, ordinary and sometimes tainted liquors.

    Most insect damage may be quite obvious to the eye but insects can also be the cause of invisible stinkers with dirty water penetrating an insect-stung or pulper-nipped bean during fermentation and causing an internal chemical reaction. Such beans may look sound on the outside but can throw unclean or even fermented cups that degrade an entire consignment.

    Insect and pest damage can be controlled only in the field. Eliminating damaged beans after harvesting costs more and does not address the root cause of the problem. However, the flotation (grading by density) of cherry before pulping is of great importance, as is the subsequent separation of parchment into lights and heavies in the washing and grading channel. These are important principles of wet processing. Smallholders who use hand pulpers should try floating the lights off in a bucket or basin filled with water before pulping - usually this makes a major difference to the end product.

    Failing this, the coffee miller's best friend, the gravity table, presents the best and cheapest option for eliminating damaged and light beans. But of course the table works well only if it is properly set and operated: the attendants must know why they are doing what they are doing. Catadors (pneumatic separation using blast air) do the same job but less efficiently, and work best if the coffee has first been size graded.

    This is not the place to argue for or against the wet processing or washing of coffee. There is no doubt however that correctly operated washing stations are an important quality control tool, at the very start of the processing chain.
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