Detailed explanation of two methods in the processing of Coffee fresh beans

Wet treatment method

Wet treatment requires the use of specific instruments and equipment and a large amount of water. When properly operated, it can ensure that the original quality of coffee beans is better preserved, producing homogeneous coffee beans with few bad beans. As a result, coffee beans produced in this way are generally considered to be of better quality and charge higher prices.

Even after careful harvest, a certain amount of partially dried and unripe coffee fruit, as well as some small stone words, dust and so on, will appear in the ripe coffee fruit more or less. In the drying method, the initial classification and washing of coffee fruits are usually necessary and should be completed as soon as possible after harvest. The operation of washing coffee beans can be done in a container full of running water. Sieves can also be used at this time to help separate ripe and unripe, large and small coffee fruits.

After sorting and cleaning, the fleshy part will be removed from the coffee fruit, which is the key to the difference between drying and wet treatment, because in the wet treatment, the flesh of the fruit is removed before the drying stage. The work of removing the pulp is done by a machine with a fixed surface and a moving surface to crush the coffee fruit. The flesh and skin of the fruit are left on one side while the beans wrapped in parchment are left on the other. The spacing between the surfaces is just right to avoid damage to the coffee beans. Pulp removal should be carried out as soon as possible after harvest to prevent the fruit from deteriorating and affecting the quality of coffee beans. The unfleshed coffee beans are then transported to a sieve to separate the unfleshed or impure coffee fruits, as well as some of the large pulp left with the beans. Then, the pulp-removed coffee beans separated through a sieve will pass through a sink, where further flotation separation is done before being sent to the next stage. Since the pulp removal work is performed by the machine, this means that it will always miss the residual pulp, glue attached to the parchment around the beans, etc., which must be removed so as not to degrade the finished product due to the dirt of the coffee beans. The fresh coffee bean is placed in a huge fermentation container where the glue is crushed and destroyed by the natural enzyme until it is dispersed, and then it can be washed off. Only by carefully monitoring the fermentation process can coffee beans get a satisfactory fermentation taste. For most coffee bean gums, the removal process takes 24 to 36 hours, depending on temperature, thickness of the glue surface, and enzyme concentration. The end of the fermentation process is determined by the feel of the parchment, as the texture of the parchment of the coffee beans changes unbalanced and produces a rougher pebble-like feel.

After the fermentation process is completed, all the coffee beans will be rinsed into containers filled with clean water or by a special cleaning machine. At this stage, the humidity of wet parchment coffee beans is about 57%. To reduce humidity to 12.5%, coffee beans are dried in the sun or in a dryer, or both. Sun drying is done on a wide range of flat or brick floors, straw mats, or tables made of good quality silk thread. The coffee beans are spread in a layer of 2x10 centimeters and need to be turned from time to time to ensure that they are really dry. It takes 8 to 10 days for the sun to dry, depending on the outside temperature and humidity. Coffee beans can dry faster if left on the table because of the ventilation of the upward warm air. If you want to speed up large farm plantations at the peak of the harvest season, it is necessary to use a dryer that uses hot air, as there are so many more coffee beans that can be dried effectively in trapezoidal fields. However, this process must be carefully controlled to achieve a satisfactory and economical drying effect without causing quality damage.

After drying, coffee beans made by wet treatment, or parchment coffee beans as they are called, are stored and retained until the eve of export.

The final stage of coffee bean preparation, known as "smoking", is usually carried out in specific factories and just before the coffee export trade. Coffee beans are removed from the inner skin of parchment and then subjected to a series of cleaning, screening, classification and grading operations, which are suitable for both wet treatment and drying. Electronic sorting machines can be used to remove bad beans, including those that are so-called smelly and difficult to identify with the naked eye.

Wet treatment is generally used in the production of all Arabica coffee except those produced in Brazil and the countries mentioned above that produce Arabica coffee by drying. Roberts coffee is rarely wet-treated.

A coffee bean is a seed in a cherry-like fruit whose epidermis (outer epidermis) appears red when it is ripe. Each fruit is wrapped in a parchment-like skin, and under the flesh (that is, in the middle of the flesh) lies two coffee beans with flat sides leaning together. When the fruit is ripe, the parchment is wrapped in a thin, thin layer of glue. The beans under the parchment are covered with another thinner film, which is a silver peel (seed coat). Each cherry fruit, generally speaking, contains two coffee beans; if there is only one, it must have a more round shape, called pea-shaped coffee beans. Coffee beans must be removed and dried before roasting; this process can be done in two days and can be dried or wet. When this process is completed, the coffee beans to be roasted are called raw coffee beans.

Drying method

The drying method, also known as the natural method, is the oldest and simplest and does not require any machines. This method involves drying the whole cherry fruit. There are also many differences in the implementation of this process, depending on the size of the farm plantation, the equipment available and the final quality required. The basic three steps are cleaning, drying and peeling, which are described in detail below.

First of all, harvested cherry fruits are usually sorted and washed, picking out the unripe, overripe and damaged ones, and removing dust, soil, twigs and leaves. This is usually done by hand, using a large sieve. Any unwanted cherry fruit and other substances can be left at the top of the sieve and picked out. Ripe cherry fruits are also separated by flotation in the sink, which is close to the stage of drying. The coffee fruit is spread out in the sun, on a large concrete floor, on a brick platform or on a straw mat lifted to the middle of the fork. As the coffee fruit dries, apply a hand rake or turn it over to make sure it is drier. It takes about 4 weeks for the coffee fruit to dry to the best humidity of 12.5%, depending on the weather. On larger farms or plantations, a dryer is sometimes used to speed up the process after the coffee fruit is exposed to the sun for a few days in advance. The drying process is the most important stage of the whole process, as it will affect the final quality of raw coffee beans. Overdried coffee beans become brittle and can lead to a lot of broken beans (which are considered bad beans) when peeled. On the other hand, coffee beans that are not completely dry will be too wet and can easily deteriorate quickly once bacteria invade.

Dried coffee fruits will be stored in special soil piles until they are transported to mills, peeled, sorted, graded, and packaged. These processes will be carried out there. The outer skin of all dried coffee fruits is removed in the steps performed by the peeling machine.

Ninety-five percent of Arabica coffee produced in Brazil is dried, and the vast majority of coffee in Ethiopia, Haiti and Paraguay is also produced in this way. It is also used to produce some Arabica coffee in India and Ecuador. Almost all Robster coffee is produced in this way. This method is not practical in areas where the air is humid or where the harvest season is often rainy next month.