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  • 11.9.2-COFFEE QUALITY-WET PROCESSING OF ROBUSTA

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  • Wet processing of robusta

     
     
    The natural wet process helps to mute and mellow the striking notes of fruit and bitterness that are often at the core of the robusta cup. Wet processing helps in developing 'soft buttery notes' in the cup, unlike the thick 'robust' notes that are observed in the average robusta cup. In a number of import markets, quality washed robusta has replaced a percentage of washed arabica in coffee blends. Such robustas have not only provided the froth and bubbles for the much sought after espresso, but have also helped in reducing the price of such blends. Robusta beans with robust but clean notes of strength and fruitiness (but not fermented, i.e. with a neutral liquor) also find ready acceptance in the preparation of soluble coffee.

    Note however that the wet processing of robusta is riskier and more difficult because the mucilage in robusta coffee is thicker and stickier than it is in arabica. In some cases fermentation may not be complete even after 72 hours and, considering the high temperatures at the low altitude at which most robusta is grown, the process requires extremely careful monitoring to avoid over-fermentation. Such lengthy fermentation periods also require much more tank space than the average processing facility can economically operate. This has led to the development of frictional stripping of the mucilage, using so-called aqua pulpers. This procedure is costly in terms of power and water consumption and is therefore of little use to small growers and smallholders.

    However, the development of mobile, motorized processing units that combine depulping and frictional mucilage removal with minimal water use is creating new opportunities for smaller growers and smallholders to benefit from the growing demand for wet processed robustas. Some are combined with mechanical drying units to ensure rapid and uniform drying, thus avoiding the risk of secondary fermentation or off flavours. For information on such types of machines go to www.penagos.com and www.pinhalense.com.br

    Defectives and off-tastes found in robusta, and their causes, do not differ markedly from those covered in the preceding section. All the concerns and limitations concerning quality and moisture content already stated are equally valid for robusta coffee, both dry and wet processed. Nevertheless it is appropriate to review some of them in the context of robusta production. See also 11.09.03 Defects in robusta coffee.