Most producers of washed Arabica cog fees use selective harvesting. Wet processing after strip harvesting is only the case for Arabicas in Brazil, Hawaii and Australia.
Coffee cherries may undergo dry, semi-dry or wet processing as soon as possible after harvesting. The storage of fresh cherries in bags, heaps, hoppers or silos should not last more than 8 hours. Otherwise unwanted fermentation will generate the dreaded “stinker” beans, which appear when the temperature before pulping exceeds 40-42°C. Even if the temperature does not rise to the point of creating stinkers, uncontrolled fermentation may have other negative impacts on the cup. In emergency situations fresh cherries may be stored for a longer period if they are kept under water. Coffee cherries should not be kept in plastic bags. The damp airtight atmosphere that develops inside plastic bags favors unwanted fermentation that damages coffee quality .
Dry-processing. Most often dry processing is used after non-selective harvesting, i.e. after stripping or mechanical harvesting. In this case, when the coffee reaches the processing line it is a mixture of unripe, ripe, overripe and partially dry cherries along with leaves and sticks as well as earth and stones when coffee is harvested directly on the ground. The aim of dry processing is to clean the coffee cherries and to separate them, to the extent possible, according to their moisture content. Cherries at different moisture levels are then dried separately to obtain an evenly dried product. Unfortunately many growers who produce natural coffees simply ignore these steps and go directly from harvesting to drying without any cleaning or separation. The result is a product of lower quality. Natural coffees that have been properly dry-processed can be a quality product with their own market. Natural coffees are a basic ingredient of espresso blends and, as such, they enjoy a growing demand, especially for high-quality products. [ Cara Publikasi Jurnal Internasional ].
Although the bulk of Robusta production is dry processed, washed Robustas have been offered by some countries like India, Democratic Republic of Congo and Indonesia for many years. Recent tendencies point to a slow shift to Robusta washing in several areas of the world. Some experts claim that washed Robustas may be a good substitute for low quality Arabicas, especially in espresso blends. Some Robusta growers, particularly in Uganda and Brazil, are shifting to the pulped natural system. Dry pulping should only be attempted in cases where there are almost 100% of ripe cherries. [ Publikasi Jurnal ].
Wet processing. In conventional devices coffee cherries are pulped in a water flow. As the water content of coffee cherries is high, most pulpers can operate with little or no water provided that alterations are made to ensure that the feeding of cherries and the removal of parchment and pulp can take place without water. Research along these lines has led to a substantial reduction of water consumption in the pulping operation.
Wet processing is to remove pulp and mucilage from ripe coffee cherries in an environmentally friendly way. In order to process only fresh ripe cherries, it is necessary to harvest only such cherries or to separate the undesirable products before pulp and mucilage are removed. The description of the wet process will be divided into cleaning and separation. Most producers of washed Arabica cog fees use selective harvesting. Wet processing after strip harvesting is only the case for Arabicas in Brazil, Hawaii and Australia as well as for Robustas in a few countries. Labor shortages and high harvesting costs are, however, forcing more countries to consider stripping as a means of lowering production costs. Even if harvesting is selective, the types of products harvested must be considered when deciding which cleaning steps and pulping systems to use. When the harvested product contains only a few impurities, for instance, it may not be necessary to sift it. Flotation may be bypassed if there are no over-ripe cherries.
Arabica cherries are easier to pulp than Robusta cherries. As a result the capacity of pulpers falls when processing Robusta coffees. Raoeng pulpers should not be used in new wet mills because of their high water and energy consumption. Disk pulpers have a tendency to lose the capacity and efficiency of separation of pulp from parchment rather quickly as the bulbs wear out. Frequent monitoring and maintenance are therefore critical for optimum performance. Stones and sticks can be very damaging to all pulping systems and even more so in the case of the copper sleeves of drums pulpers. If it cannot be guaranteed that the harvested cherries are free from foreign materials, pulping should be preceded by a flotation device to remove stones and other impurities. Steel sleeves are more resistant to wear and tear and damage than copper sleeves. The generation of pulp fiber is a problem for many pulping systems. Fiber is very difficult to separate from water and high cost special equipment is required. The pulping system that produces the least fiber is the slotted screen one. A pulping system that produces whole pulp rather than pulp pieces and fiber is environmentally superior.
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