Finessing the Flow

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While the quality of each coffee bean is created in the field, poor processing can ruin all that good work. This is most critical during the pulping, mucilage removal and drying phases when cup quality – aroma, acidity, and body – can be altered.

Coffee processors constantly look for ways to preserve the quality of their beans while reducing water use and saving labor costs. Equipment manufacturers work with them to develop machinery to help the cause.

It all starts with harvested cherries that arrive in a variety of conditions. With them come stones, sand, leaves, and other impurities. As it has been for ages, incoming fruit is initially sorted by hand. Workers examine coffee cherry for ripeness, pulling over- and under-ripe cherry from each lot. They also pick out the unwanted debris.

Operations using mechanical sorters realize faster, more productive sorting with a far lower labor cost. Coffees may go through a second round using optical sorters to further reduce the number of defects in the end product.

Focus on wet processing

Wet processing, commonly used in countries where acidity is valued in the final product, requires four steps to prepare beans. Water has traditionally been central to the process but it does not necessarily help deliver brighter, cleaner, and fruitier coffee beans.

A mechanical sorter or “siphon” is used to separate cherries. During this process, all cherries are submerged in water. Those that are over-ripe float to the surface because they lack density and weight. These “floaters” are removed to be naturally dried in the sun.

The “sinkers” are retained and move to the pulping stage where the skin and pulp are gently removed taking caution not to damage the underlying parchment and mucilage. The cherry is then washed and sieved to remove any pulp or skin that remains. The collected waste is returned to the farm as fertilizer.

Now only parchment and sticky mucilage surround the bean. The mucilage contains alcohol and natural sugars and plays a key role in developing the sweetness, acidity and flavor profile during growth. That mucilage now must be removed, totally to produce washed coffee or partially to produce pulped natural coffee.

To do this, beans are placed in cements tanks, commonly three feet deep. Enzymes naturally ferment in the water and break down the mucilage. This ferment-and-wash process requires time and large amounts of water.

After washing, the beans are dried. This can be done outdoors under the sun or within drying machines if speed is important or when rains persist.

Removing pulp and mucilage

While dry gravity separators are used to shake and vibrate the good cherries from the bad, wet processing remains a popular process despite the need for water.

Brazilian equipment manufacturer Pinhalense has developed its LSC mechanical siphon to sort the ripe from the over-ripe. The LSC uses far less water than conventional siphon tanks and speeds the sorting of over-ripe floaters, commonly used in Brazil where naturals are central to both exports and local consumption.

The LSC siphon recycles the little water it uses and continuously discharges stones and other impurities without human labor. Removing these elements is critical to avoid damage to the pulper and mucilage removal machine farther down the processing line. The LSC siphon can be combined with other Pinhalense machines or operate alone.

Pinhalense is completing field tests on a new ECO SUPER D pulper that requires no water. The ECO SUPER D, to become available for exports in the second quarter of 2017, handles four tons of cherries per hour per module.

Here’s how it works. As the cherries flow through the machine, adjustable size screens discard the unripe cherries at the same time they separate the pulp and skin from parchment with no damage to it. The pulp and skin are then discharged and returned to the plantation as compost. The remaining parchment move on to fermentation, the mucilage remover or a combination of both.

The remover then uses tiny metal finger-like screws to rub the beans – similar to rubbing a bean between your hands –  generating the friction needed to remove the coating. While other mucilage removal methods rely on water to speed fermentation and enzyme breakdown, the Pinhalense machine uses the lubricant within the mucilage itself.

“The mucilage remover eliminates much of the need for water,” said Carlos Brando, a partner at P&A Marketing, Pinhalense’s export manager. “The beans become slimy and the mucilage breaks down by the biological process and by friction.”

Brando said Pinhalense has been developing the new equipment more than a year. “We dramatically changed what’s on the inside,” he said. “We’re squeezing the flow to use less water.”

The first prototypes were tested in Central America, Brando said, before successful trials in Brazil during April and May. “It’s ready for the Brazilian market to be used next harvesting season,” he said, and it will be available for exports from April 2017 onward.

Dry processing

Dry processing, on the other hand, allows the moisture in each cherry to naturally evaporate much like a grape becomes a raisin. This is typically done in countries – such as Brazil, Ethiopia and Yemen. Cherries dry with the pulp and mucilage and, for this reason, dry-processed beans are called “naturals.”

The naturals are turned by hand or raked to make sure they all dry evenly. It can take as long as three weeks for a cherry to dry to the target 12% moisture content. Only then is the dried fruit hulled and bagged for shipment. Mechanical drying significantly reduces drying time.

Finessing the Flow

Finessing the Flow

Ricardo Koyner of Kotowa Coffee in Panama, with his Pikasen FMS-2000 compact optical sorter. In 2015 Kotowa Coffee was the first green coffee processor in Latin America to install this technology.

New sorting solutions

The goal of processing equipment manufacturers is to develop machinery that speed the process and provide labor efficiencies.

“A challenge that becomes more complicated as the years go by is the cost of labor,” said Johanna Bot, director of sales, vision systems-Latin America and Caribbean for Satake USA. “In many places, human hands still touch and interact with the coffee beans throughout the production and processing flow. This can introduce a host of new problems due to human error, sanitation and other issues.  Some countries are starting to do more mechanical harvesting in the field in order to rely less on human labor.”

Sorting manufacturer Satake offers optical sorters as precision alternatives to the hand-sorting of green and roasted coffee. Optical sorting, sometimes called digital sorting, relies on sophisticated cameras to identify defects and foreign material by color. The sorter examines each object based on user-defined parameters and accepts or rejects each piece accordingly.

Satake Evolution series and the Pikasen FMS-2000 sorters. The FMS is a compact, full-color RGB optical sorter designed for small and medium-size qantities. It uses low-energy lighting that evenly illuminates on each coffee bean and has an average lifespan of 20,000 hours.

The Evolution series is designed for large capacity production using full color RGB lighting the ability to reveal defects in the purest light.

The last sort

Specialty roasters often employ a final tier of sorting to avoid the off-putting scent of foreign material.

Probat, a roaster manufacturer based in Germany, recently teamed with Belgian-based Tomra Sorting Food to provide a free-fall laser sorter called the LST. Based on the existing Tomra Nimbus food sorter, the LST simultaneously identifies quality cherry while rejecting less desirable fruit and foreign objects. Unwanted and difficult to detect objects such as little sticks or green coffees of very heterogeneous color are easily identified and discolored and deformed green or roasted coffee are rejected with extremely high efficiency.

Incoming products are analyzed and the best sorting parameters are automatically selected for creating a higher level of contrast which results in a lower false reject and the highest possible efficiency.

The high-resolution laser technology, Probat states, will recognize objects not detected by conventional sorters and is capable to recognizing items based on biological characteristics.