The final steps in coffee processing involve removing the last layers of dry skin and remaining fruit residue from the now-dry coffee, and cleaning and sorting it. These steps are often called dry milling to distinguish them from the steps that take place before drying, which collectively are called wet milling.
The first step in dry milling is the removal of what is left of the fruit from the bean, whether it is the crumbly parchment skin of wet-processed coffee, the parchment skin and dried mucilage of semi-dry-processed coffee, or the entire dry, leathery fruit covering of the dry-processed coffee. Hulling is done with the help of machines, which can range from simple millstones to sophisticated machines that gently whack at the coffee.
This is an optional process in which any silver skin that remains on the beans after hulling is removed in a polishing machine. This is done to improve the appearance of green coffee beans and eliminate a by-product of roasting called chaff. It is described by some to be detrimental to the taste by raising the temperature of the bean through friction which changes the chemical makeup of the bean.
Most fine coffee goes through a battery of machines that sort the coffee by density of bean and by bean size, all the while removing sticks, rocks, nails, and miscellaneous debris that may have become mixed with the coffee during drying. First machines blow the beans into the air; those that fall into bins closest to the air source are heaviest and biggest; the lightest (and likely defective) beans plus chaff are blown in the farthest bin. Other machines shake the beans through a series of sieves, sorting them by size. Finally, a machine called a gravity separator shakes the sized beans on a tilted table, so that the heaviest, densest and best vibrate to one side of the pulsating table, and the lightest to the other.
Ethiopian women sort coffee beans at a long table.
The final step in the cleaning and sorting procedure is called colour sorting, or separating defective beans from sound beans on the basis of colour rather than density or size. Colour sorting is the trickiest and perhaps most important of all the steps in sorting and cleaning. With most high-quality coffees colour sorting is done in the simplest possible way: by hand. Teams of workers pick discoloured and other defective beans from the sound beans. The very best coffees may be hand-cleaned twice (double picked) or even three times (triple picked). Coffee that has been cleaned by hand is usually called European preparation; most specialty coffees have been cleaned and sorted in this way.
Colour sorting can also be done by machines. Streams of beans fall rapidly, one at a time, past sensors that are set according to parameters that identify defective beans by value (dark to light) or by colour. A tiny, decisive puff of compressed air pops each defective bean out of the stream of sound beans the instant the machine detects an anomaly. However, these machines are currently not used widely in the coffee industry for two reasons. First, the capital investment to install these delicate machines and the technical support to maintain them is daunting. Second, sorting coffee by hand supplies much-needed work for the small rural communities that often cluster around coffee mills. Nevertheless, computerized colour sorters are essential to coffee industries in regions with relatively high standards of living and high wage demands.
Grading is the process of categorizing coffee beans on the basis of various criteria such as size of the bean, where and at what altitude it was grown, how it was prepared and picked, and how good it tastes, or its cup quality. Coffees also may be graded by the number of imperfections (defective and broken beans, pebbles, sticks, etc.) per sample. For the finest coffees, origin of the beans (farm or estate, region, cooperative) is especially important. Growers of premium estate or cooperative coffees may impose a level of quality control that goes well beyond conventionally defined grading criteria, because they want their coffee to command the higher price that goes with recognition and consistent quality.
Business Name: Coffee Grind, Bean Heaven, Black Bean Pod.
Coffee name: Serenity, coffee stirrer, awakener, nutty.
After coffee is harvested, it undergoes a processing method in which the coffee beans are removed from the raw fruit. There are various techniques of processing coffee; each technique impacts the final flavor of the end product. These are three main methods:
In the wet process, the fruit covering the seeds/beans is removed before they are dried. Coffee processed by the wet method is called wet processed or washed coffee. The wet method requires the use of specific equipment and substantial quantities of water.
The coffee cherries are sorted by immersion in water. Bad or unripe fruit will float and the good ripe fruit will sink. The skin of the cherry and some of the pulp is removed by pressing the fruit by machine in water through a screen. The bean will still have a significant amount of the pulp clinging to it that needs to be removed. This is done either by the classic ferment-and-wash method or a newer procedure variously called machine-assisted wet processing, aqua pulping or mechanical demucilaging.
In the ferment-and-wash method of wet processing, the remainder of the pulp is removed by breaking down the cellulose by fermenting the beans with microbes and then washing them with large amounts of water. Fermentation can be done with extra water or, in “Dry Fermentation”, in the fruit’s own juices only.
The fermentation process has to be carefully monitored to ensure that the coffee doesn’t acquire undesirable, sour flavours. For most coffees, mucilage removal through fermentation takes between 24 and 36 hours, depending on the temperature, thickness of the mucilage layer, and concentration of the enzymes. The end of the fermentation is assessed by feel, as the parchment surrounding the beans loses its slimy texture and acquires a rougher “pebbly” feel. When the fermentation is complete, the coffee is thoroughly washed with clean water in tanks or in special washing machines.
In machine-assisted wet processing, fermentation is not used to separate the bean from the remainder of the pulp; rather, this is done through mechanical scrubbing. This process can cut down on water use and pollution since ferment and wash water stinks. In addition, removing mucilage by machine is easier and more predictable than removing it by fermenting and washing. However, by eliminating the fermentation step and prematurely separating fruit and bean, mechanical demucilaging can remove an important tool that mill operators have of influencing coffee flavour. Furthermore, the ecological criticism of the ferment-and-wash method increasingly has become moot, since a combination of low-water equipment plus settling tanks allows conscientious mill operators to carry out fermentation with limited pollution.
Any wet processing of coffee produces coffee wastewater which can be a pollutant. Ecologically sensitive farms reprocess the wastewater along with the shell and mucilage as compost to be used in soil fertilization programs. The amount of water used in processing can vary, but most often is used in a 1 to 1 ratio.
After the pulp has been removed what is left is the bean surrounded by two additional layers, the silver skin and the parchment. The beans must be dried to a water content of about 10% before they are stable. Coffee beans can be dried in the sun or by machine but in most cases it is dried in the sun to 12-13% moisture and brought down to 10% by machine. Drying entirely by machine is normally only done where space is at a premium or the humidity is too high for the beans to dry before mildewing.
When dried in the sun coffee is most often spread out in rows on large patios where it needs to be raked every six hours to promote even drying and prevent the growth of mildew. Some coffee is dried on large raised tables where the coffee is turned by hand. Drying coffee this way has the advantage of allowing air to circulate better around the beans promoting more even drying but increases cost and labour significantly.
After the drying process (in the sun or through machines), the parchment skin or pergamino is thoroughly dry and crumbly, and easily removed in the hulling process. Coffee occasionally is sold and shipped in parchment or en pergamino, but most often a machine called a huller is used to crunch off the parchment skin before the beans are shipped.
Dry process, also known as unwashed or natural coffee, is the oldest method of processing coffee. The entire cherry after harvest is first cleaned and then placed in the sun to dry on tables or in thin layers on patios:
The harvested cherries are usually sorted and cleaned, to separate the unripe, overripe and damaged cherries and to remove dirt, soil, twigs and leaves. This can be done by winnowing, which is commonly done by hand, using a large sieve. Any unwanted cherries or other material not winnowed away can be picked out from the top of the sieve. The ripe cherries can also be separated by flotation in washing channels close to the drying areas.
The coffee cherries are spread out in the sun, either on large concrete or brick patios or on matting raised to waist height on trestles. As the cherries dry, they are raked or turned by hand to ensure even drying and prevent mildew. It may take up to 4 weeks before the cherries are dried to the optimum moisture content, depending on the weather conditions. On larger plantations, machine-drying is sometimes used to speed up the process after the coffee has been pre-dried in the sun for a few days.
The drying operation is the most important stage of the process, since it affects the final quality of the green coffee. A coffee that has been overdried will become brittle and produce too many broken beans during hulling (broken beans are considered defective beans). Coffee that has not been dried sufficiently will be too moist and prone to rapid deterioration caused by the attack of fungi and bacteria.
The dried cherries are stored in bulk in special silos until they are sent to the mill where hulling, sorting, grading and bagging take place. All the outer layers of the dried cherry are removed in one step by the hulling machine.
The dry method is used for about 90% of the Arabica coffee produced in Brazil, most of the coffees produced in Ethiopia, Haiti and Paraguay, as well as for some Arabicas produced in India and Ecuador. Almost all Robusta’s are processed by this method. It is not practical in very rainy regions, where the humidity of the atmosphere is too high or where it rains frequently during harvesting.
Semi-dry is a hybrid process used in Indonesia and Brazil. The process is also called “wet-hulled”, “semi-washed”, “pulped natural” or, in Indonesia, “Gilling”. Literally translated from Indonesian, Gilling Basah means “wet grinding”. This process is said to reduce acidity and increase body.
Most small-scale farmers in Sumatra, Sulawesi, Flores and Papua use the gilling basah process. In this process, farmers remove the outer skin from the cherries mechanically, using locally built pulping machines. The coffee beans, still coated with mucilage, are then stored for up to a day. Following this waiting period, the mucilage is washed off and the parchment coffee is partially dried in the sun before sale at 10% to 12% moisture content.
The tricky part during the semi-washed process method are bacteria which are always around. Fermentation can start immediately as honey dried coffee beans have a remaining “sugar” layer which is vulnerable to any sort of mould and offers feeding ground for bacteria. Drying carefully and under supervision is crucial to the success of this processing methods. The beans need to constantly move during the drying process to prevent molt and fungal infections. The processor need to rack the green coffee beans 2-3 times per hour to ensure a safe drying process. Once the beans reached a sufficient moist level, again, the beans are dry milled to remove the “parchment” layers and are sent off the roasters and wholesalers globally.
Honey processing bridges the gap between washed and natural coffees as it generally possesses some of the body and sweetness of a natural while retaining some of the acidity of a washed. Honey coffees often have a syrupy body with enhanced sweetness, round acidity and earthy undertones.
Green coffee is usually transported in jute bags or woven poly bags. While green coffee may be usable for several years, it is vulnerable to quality degradation based on how it is stored. Jute bags are extremely porous, exposing the coffee to whatever elements it is surrounded by. Coffee that is poorly stored may develop a burlap-like taste known as “bagginess”, and its positive qualities may fade.
In recent years, the specialty coffee market has begun to utilize enhanced storage method. A gas barrier liner to jute bags, is sometimes used to preserve the quality of green coffee. Less frequently, green coffee is stored in vacuum packaging; while vacuum packs further reduce the ability of green coffee to interact with oxygen at atmospheric moisture, it is a significantly more expensive storage option.
Although not considered part of the processing pipeline proper, nearly all coffee sold to consumers throughout the world is sold as roasted coffee in general one of four degrees of roasting: light, medium, medium-dark, and dark. Consumers can also elect to buy unroasted coffee to be roasted at home.
• The demand for Cold-drip coffee is growing in Australia. Cold-drip coffee is prepared one drop at a time, to have a subtle taste with low acidity and bitterness. Housed in a converted warehouse in South Melbourne, it is one of the best places to try this brew. Further, the Central Melbourne, Krimper and Manchester Press are the few top spots to taste this cold-drip coffee.
• Nitro Coffee is another key product that interests consumers. Nitro coffee is poured from a tap and provides a similar mouth feel as a beer. The foamy and creamy texture of Nitro coffee allows brewers to add less milk and sugar, to cut off the bitter taste, however, it is appealing to the health-conscious coffee drinker. Moreover, the texture is difficult to replicate in an RTD coffee, giving cafes something extra to offer the millennial, looking for unique drinking experiences.
• “Arabica holds the highest share in the coffee market”
• The Australia coffee market, based on type, has been segmented into Arabica, Robusta and Liberica. Arabica holds the largest share, followed by Robusta and Liberica. By product type, the market is segmented into whole-bean, powder, instant coffee and others. Further, the other product category includes coffee pods, capsules, etc. Based on flavour, the market is categorized into flavor and non-flavour, where the instant coffee segment is growing faster. The convenience and versatility, in terms of flavour and aroma, of instant coffee make it an attractive drink for the consumers. Flavour is further segmented into vanilla, caramel, Irish cream, hazelnut and others. Moreover, the process category consists of two, namely, caffeinated and de-caffeinated segments, where the caffeinated coffee holds the largest market share of about 80%.