Is the listing of coffee futures in preparation? This popular science article is perfect for reading while drinking coffee

Coffee is the first of the three major beverage crops in the world and the second raw material product in the world after oil. Coffee is rich in protein, crude fiber, crude fat, caffeine, etc. Because of its unique mellow taste and refreshing and exciting effects, it has gradually become an indispensable daily drink for people today. About one-third of the world's population drinks it.

The basic concept and origin of coffee

1. Basic Concept of Coffee

(1) Coffee tree

Coffee trees are perennial evergreen shrubs or small trees of the Rubiaceae family. They are a horticultural perennial cash crop that is fast-growing, high-yielding, high-value, and widely marketed . Wild coffee trees can grow to 5 to 10 meters high, but coffee trees planted in manors are often pruned to a height of less than 2 meters to increase the yield and facilitate harvesting. The opposite leaves of coffee trees are oblong and smooth, with long branches at the end and few branches. The flowers are white and bloom at the base of the petiole connecting the branches.

The first flowering period of a coffee tree is about three years old. After that, it blooms around March every year, withers after 2-3 days, and produces coffee berries a few months later. The diameter of the coffee berries is about 1.5 cm. It is green at first, then gradually turns yellow, and turns red when mature. It looks like a cherry, so it is also called coffee cherry or coffee berry. Depending on the planting area and tree species, the number of years that a coffee tree can produce berries varies from 10 to 20 years.

(2) Green coffee beans

Green coffee beans are the seeds of the coffee tree. They are the treasure hidden in what people usually call coffee cherries (coffee berries). They are mistakenly called "beans" because they are very similar to the beans we usually see, but they are actually coffee seeds. Usually there are two flat and oval green coffee beans in the coffee berries, and a small number of coffee berries have only one green coffee bean, just like there is only one grain of rice in a paddy, and this kind of bean is called Peaberry (round bean). When coffee beans are exported, they are almost all green beans, and each bag usually weighs 60 kg, 69 kg or 70 kg.

(3) Roasted coffee beans

Roasted coffee beans, also known as roasted coffee beans, refer to coffee beans that have been roasted. They are brown or dark brown and can be ground and drunk directly. Green coffee beans contain more than 200 volatile substances, but they have no fragrance and are inedible. Roasting green coffee beans will produce a large amount of volatile aromatic compounds, giving off a rich coffee aroma. The quality of coffee bean roasting directly determines the quality of the coffee bean aroma.

2. Origin

The discovery of coffee originated from the legend of Ethiopian shepherds in the early 7th century. Its processing and drinking have gone through the following process:

Arabs began drinking coffee in the 8th century, when they used it as a stimulating drink and medicine for religious activities.

In the 9th century, people in the Middle East, mainly in the Arab region, began to roast and grind coffee beans, and coffee has developed into a daily drink for people in the local area.

In the 10th century, Arab merchants brought coffee to Europe. At that time, Europeans did not regard coffee as a beverage, but drank it as wine.

In the 13th century, the Turks began to roast coffee beans and brew coffee for drinking.

In the 14th century, coffee drinking became popular in Türkiye, Syria and other Middle Eastern regions. The earliest coffee shop was born in Türkiye, and coffee gradually entered households.

Turkish coffee appeared in the 15th century, and its brewing method has been used to this day. Coffee has evolved from a functional beverage and a formula medicine to a popular beverage.

In the 16th century, coffee and coffee houses were already very common in the Islamic world, but coffee houses were once banned by rulers because they became "the gathering place of public opinion" and "the center of political debate." The strict ban did not stop people from loving coffee, and many people still drank coffee without fear of punishment, so the ban was eventually lifted.

Coffee was introduced to North America in the 17th century, and coffee houses appeared in Italy, Britain, France and other countries, starting a coffee drinking craze. Coffee was favored by the European upper class. By the end of the 17th century, coffee houses for people to gather and chat could be seen everywhere in Europe.

In the 18th century, Java sent coffee to the Netherlands for the first time, and the first coffee house opened in Berlin. The French transplanted coffee trees to the Andes Islands, the Portuguese transplanted coffee trees to Brazil, the British transplanted coffee trees to Jamaica, Cuba and Central America, and the Spanish transplanted coffee trees to Colombia.

Coffee cherries classification

1. The structure of coffee cherries

The fruit picked from the coffee tree is usually called coffee berry or coffee cherry. Coffee berry consists of four parts: peel (exocarp), pulp (mesocarp), pectin and shelled beans.

The pulp of coffee berries is not thick and tastes sweet. Pectin is a layer of gelatinous pulp between the skin and seeds of coffee berries. It is thick and sticky. Shelled beans, also known as parchment coffee beans, refer to coffee seeds that have been processed but still have a protective layer. Shelled beans are the main form of storage and transportation in coffee producing countries. They are usually sent to the mill for shelling before being prepared for export.

Shelled beans are made up of three parts: parchment (endocarp), silverskin, and embryo. The parchment is a paper-like shell that wraps around the green coffee beans, which is equivalent to a protective layer for the seeds and can keep the green coffee beans fresh. The better the quality of the coffee, the thicker the parchment. The silverskin is a thin film attached to the green beans (including the center line part), located between the parchment and the green beans, and is the last layer of protective film for the coffee beans. During the roasting process of the coffee beans, the silverskin will loosen and fall off, but some will remain at the center line, which is called the "inner silverskin". The embryo is what we often call green coffee beans, which consists of four parts: endosperm, cotyledon, radicle, and hypocotyl.

2. Classification of coffee beans

There are about 40 species of coffee plants, but only Arabica, Robusta, and Liberica can produce coffee beans with commercial value. These three are called the "three major native species of coffee."

(1) Arabica (scientific name: Coffea arabica)

Arabica coffee, also known as small-grain coffee, is native to Ethiopia and grows in tropical, cold, high-altitude areas. It has low resistance to dryness, frost damage, pests and diseases, especially leaf rust, and is difficult to grow. Its production accounts for more than 70% of the world's coffee production. Arabica coffee beans are slender and flat, with an S-shaped central line and a caffeine content of about 1.5%. Arabica coffee has an elegant flavor and is the only native coffee that can be drunk directly. It is also the main force of boutique coffee. Generally speaking, better quality and more expensive coffee beans all come from Arabica coffee beans, such as the world-famous Hawaii Kona, Jamaica Blue Mountain and Yemen Mocha. The main production areas of Arabica coffee beans are South America (excluding Argentina and parts of Brazil), Central America, Africa (Kenya, Ethiopia, etc., mainly East African countries), and Asia (including Yemen, India, and parts of Papua New Guinea).

(2) Robusta (Coffea robusta Linden)

Robusta coffee, also known as medium-grain coffee, is native to Congo, Africa. It grows in hot and humid low-altitude areas. It has stronger disease resistance than Arabica, is resistant to leaf rust, and is easy to cultivate. Its output accounts for about 20-30% of the world's coffee output. Robusta coffee beans are rounder, with a C-shaped central line and a caffeine content of about 3.2%. Robusta coffee tastes bitter and has a rough flavor. It cannot be drunk alone. It is generally used in industrial coffee production such as instant, canned, and liquid coffee. The main producers of Robusta are Indonesia, Vietnam, and West African countries centered on Cote d'Ivoire, Algeria, and Angola. In recent years, Vietnam has been committed to becoming a major coffee producer and has included coffee production in its national policy (Vietnam also produces some Arabica coffee).

(3) Coffea liberica

Liberian coffee, also known as large-grain coffee, is native to West Africa. It has strong adaptability to the environment, is not resistant to leaf rust, is planted in a small area, and its output accounts for only about 5% of the world's coffee output. The top of Liberian coffee beans is pointed and diamond-shaped, with poor aroma and strong bitterness.

The main ingredients of coffee

1. Chemical composition

(1) Water content

The moisture content of coffee beans varies greatly with different processing stages and products. The moisture content of wet coffee beans with film is about 50%, while the moisture content of dry green coffee beans is about 10%~13%, and the moisture content of roasted coffee beans is only about 5% or less. Instant coffee powder made by spray drying or freeze drying has the lowest moisture content, generally less than 3%.

(2) Minerals

Although the content of minerals in coffee beans is relatively small, accounting for about 4% of the dry weight of raw coffee beans, it is very important. It contains a variety of different elements, among which potassium is the largest, accounting for about 40% of all minerals, followed by calcium, magnesium, phosphorus, sodium and sulfur. Other trace elements include zinc, manganese, copper, rubidium, etc.

(3) Carbohydrates

Carbohydrates contribute to the taste, aroma and color of coffee. The carbohydrates contained in coffee beans can be divided into polysaccharides and low molecular weight sugars. Polysaccharides are a very important component of green coffee beans, accounting for about 40%-50% of the dry matter.

(4) Chlorogenic acid

Chlorogenic acid is also known as coffee tannin, and its chemical formula is C16H18O9. A lot of it is lost during the roasting process, and it decomposes to produce quinic acid. In 1932, people discovered chlorogenic acid in coffee beans. Both raw coffee beans and roasted coffee beans contain a lot of chlorogenic acid that is beneficial to human health. The antibacterial, antiviral, white blood cell increasing, antioxidant, free radical scavenging, and anti-cancer effects of coffee that we understand in daily life are closely related to chlorogenic acid.

(5) Tannic acid

Tannic acid is also known as tannic acid and tannic acid, and its chemical formula is C76H52O46. Tannic acid in coffee beans will decompose to produce pyrotannic acid after boiling, which will make the coffee taste worse. If the coffee is brewed and then left for several hours, the color will become thicker than when it was just brewed, and the taste will become worse.

(6) Other acids

In addition to chlorogenic acid and tannic acid, coffee beans also contain many other acids, such as citric acid, malic acid, acetic acid, quinic acid, tartaric acid, phosphoric acid, etc.

(7) Protein and amino acids

Calculated in crude protein, the protein content of green coffee beans is about 13%~16%. If nitrogen-containing compounds such as caffeine and fenugreek are deducted, the actual protein content is about 8.8%~9.7%. Green coffee beans also contain a variety of enzymes, such as lipase, protease, carbohydrate-degrading enzyme, galactose hydrolase and peroxidase. Green coffee beans contain about 0.15%-0.25% free amino acids, which have a greater impact on the flavor of coffee and less impact on the taste.

(8) Fat

The fat in coffee plays an extremely important role in the flavor. There are many types of fat in coffee, and the most important ones are acidic fat and volatile fat. Acidic fat refers to fat with acidity that varies depending on the type of coffee. Volatile fat is the main source of coffee aroma, and it is a substance that emits about 40 kinds of aroma. Once the fat in roasted coffee beans comes into contact with air, it will undergo chemical changes and the taste and aroma will deteriorate.

(9) Caffeine

Caffeine is the most notable of all the ingredients in coffee. Most of the bitterness in coffee comes from it. It is a type of phytoxanthin (animal muscle component) and has the same properties as theobromine in cocoa and theophylline in green tea. The percentage reduction after roasting is extremely small. The most significant physiological effect of caffeine on the human body is its stimulation of the central nervous system. It can accelerate the body's metabolism and keep people awake and sharp-minded.

2. Nutritional content of coffee

Coffee is rich in caffeine, caffeic acid, chlorogenic acid and other ingredients, which can effectively resist free radicals that threaten our health. Free radicals are the main cause of many diseases (such as myocardial disease, arteriosclerosis, stroke, emphysema, Parkinson's disease). Caffeine can stimulate the central nervous system and muscles, so it can boost spirits, enhance thinking ability, and restore muscle fatigue. It acts on the cardiovascular system, improves heart function, dilates blood vessels, and promotes blood circulation. For the gastrointestinal system, it can help digestion and help break down fat.

The nutritional content of coffee beans per 100 grams is shown in the following table

The nutritional content of each 100 grams of coffee extract is shown in the following table

Coffee planting cycle and influencing factors

1. Growth stage

(1) Coffee tree planting cycle

Coffee trees are perennial cash crops. It takes about 3-5 years from sowing and transplanting seedlings to growing into mature trees. The 5th to 20th year is the production period. Wild coffee trees can be up to 4-7 meters tall, while cultivated ones are pruned to about 2 meters. A coffee tree can produce about 3-5 kilograms of coffee berries each year, and its economic life is about 20-30 years.

① Seedling stage

The seedling stage is the period from the germination of seeds (or cuttings, grafting) to the emergence of seedlings (the stage of nursery seedling cultivation), which takes about 0.5-1.5 years . After the coffee seeds are sown, the cotyledons begin to emerge after a period of germination, which takes about 30-100 days. The length of time is highly correlated with temperature and humidity. After germination, the cotyledon seedlings must be moved to nutrient bags and then transplanted to greenhouses to grow into seedlings. When the seedlings grow to 40-50 cm in height, relatively healthy and sturdy seedlings are selected and transplanted to the farm, which takes about 3-12 months. This approach is more traditional, but it can ensure the quality of coffee from the source.

② Sapling stage

The sapling stage is also called the vegetative growth stage, which refers to the period from planting to production, about 2-3 years . The main feature of this period is vigorous vegetative growth, with 6-8 pairs of branches per year, with roots, stems and leaves as the center, and the above-ground and underground parts expanding rapidly to form an ideal plant structure in preparation for production.

③ First period

The initial production period refers to the period from the beginning of production to the peak production period, which is about 1-2 years . During this period, coffee begins to enter reproductive growth, and the coffee tree has vigorous vegetative growth and a high demand for nutrients. The first flowering of the coffee tree means that the coffee tree has entered the initial production period. The life span of the coffee flower is about 3-5 days. After the petals wither, small green fruits are produced. After 8-9 months, they mature and turn red to become ripe fruits that can be picked.

④ Peak production period

The peak production period begins about 1-2 years after the initial production period. After that, the trunk of the tree is cut down every 8-9 years to allow it to grow again in order to control the height of the tree. If managed properly, the production period of a coffee tree can be up to 30 years.

⑤ Aging stage

The decline in growth and the approaching end of economic life indicate that coffee has entered the aging period. After a long production period, the annual output of coffee beans gradually decreases, and the economic life of the coffee tree will come to an end. Farmers will cut down old coffee trees and replant new coffee trees due to the decline in annual output. The length of its life is closely related to climate, soil, and management level. There are still century-old coffee trees that can bloom and bear fruit.

(2) Coffee Cherry Growth Cycle

The coffee fruit matures 8-11 months after flowering, and then enters the harvest period. Because different parts of the same coffee tree bloom at different times, the flowering period, fruit development period and ripening and picking period of the coffee tree overlap partially.

① Flowering period

Coffee trees generally bloom once a year, but geographical and climatic differences lead to slightly different flowering times in different producing countries. Brazil has no high mountains and many areas have high temperatures, which causes coffee trees to bloom multiple times a year. Therefore, white flowers, green fruits, and red fruits can often be seen on the same branch. In addition, in some countries where the dry and wet seasons are not obvious, such as Colombia and Kenya, there are two flowering periods a year, that is, there are two large and small harvests, but strictly speaking, there is only one harvest a year. Usually, rainy days after the dry season are the signal for coffee flowers to bloom. Coffee flowering is greatly affected by climate, among which rainfall and temperature have the greatest impact. It will not bloom when the temperature is below 10℃, and it is conducive to flowering only when it is above 13℃, requiring less rainfall. The coffee flower is pure white with a faint jasmine fragrance. Coffee trees can bloom multiple times, with concentrated flowering periods, and the life span of the flowers is only 2-3 days, which is relatively short. After the petals wither, small green fruits will be produced.

② Fruit development period

It takes about 8-11 months for coffee to mature from flowering and pollination. The higher the altitude and the lower the temperature, the longer it takes for coffee berries to develop. Coffee berries are green at first, gradually turn yellow, and turn red or crimson when ripe. It usually takes 8-10 months for Arabica coffee to mature. Robusta coffee relies on wind or insects to transfer pollen, so it takes 9-11 months from pollination to fruit maturity, which is longer than Arabica coffee. If classified by grain type, small-grain coffee berries take about 8-10 months to develop, medium-grain coffee takes 10-12 months, and large-grain coffee takes 12-13 months.

③ Mature harvest period

Coffee berries should be harvested immediately after they are ripe. Usually, berries of different maturity stages appear on the same tree. Picking ripe and unripe berries at the same time will reduce the quality of the coffee. Therefore, harvesting is a time-consuming and labor-intensive task. Generally speaking, it takes 4-5 months from the initial harvest to the complete harvest. Coffee harvesting is divided into two methods: manual harvesting and machine harvesting. At present, manual picking is still very common. Manually picked coffee has high quality, but the labor cost is also high. The use of machine picking is more common in areas with large production and relatively low altitudes, requiring fewer people and more defects.

2. Main factors affecting growth

Climate is the decisive factor for coffee planting. Coffee trees are only suitable for growing in tropical or subtropical areas, so the area between 25 degrees north and south latitude is most suitable for growing coffee. This coffee production area is generally called the "coffee belt" or "coffee zone". However, not all lands in the "coffee belt" can grow good coffee trees. The main factors affecting coffee growth are the following six points:

(1) Temperature

The suitable temperature for growing coffee trees is usually between 15-25 degrees.

(2) Rainfall

The annual rainfall required for the growth of coffee trees must reach 1500-2000 mm. At the same time, the rainfall timing must be able to coordinate with the flowering cycle of the coffee trees. Generally, less rainfall is required during the flowering period. Heavy rain during the critical flowering period will lead to a reduction in yield; more rainfall is required during the fruit development period, especially during the flowering period and the small fruit development period. A certain amount of rainfall is most suitable for the growth and development of coffee; the harvest period must be dry, because rainfall during the harvest period will stimulate the fruit trees to bloom at an inappropriate time, resulting in difficulties in harvesting and damage to the next year's harvest.

(3) Soil

Coffee trees have a well-developed root system with shallow roots, and require loose, fertile, well-drained loam. The most suitable soil for growing coffee is well-drained, fertile soil containing volcanic ash.

(4) Altitude

The most ideal altitude is 500-2000 meters. Low-lying areas are generally not suitable for growing coffee. Coffee grows slowly in areas with high altitudes and has higher quality. Therefore, Jamaican Blue Mountain coffee grown at an altitude of 800-1200 meters has the best quality.

(5) Lighting

The average annual sunshine duration required by coffee trees is generally 1900-2200 hours. Coffee trees cannot tolerate strong light, and too strong light will inhibit the growth of coffee; but excessive shade and too long branches and leaves will lead to sparse coffee flowers and fruits and very low yields. Therefore, coffee trees need sufficient light to ensure the growth and development of fruits, and appropriate shade to avoid growth inhibition. Therefore, various production areas usually plant some shade trees, generally bananas, mangoes, legumes and other plants with tall trunks.

(6) Nutrition

Coffee trees grow best in soils rich in nitrogen, potassium carbonate and phosphoric acid.

3. Major pests and diseases

(1) Main diseases

① Coffee rust

Coffee rust is the main disease of coffee and is the most harmful. Infected plants will suffer from reduced yields in mild cases and death in severe cases. Coffee rust mainly harms leaves and sometimes young fruits and tender branches. When leaves are infected, many small light yellow spots appear at first and expand like water stains. Then there are piles of orange-yellow powdery spores on the back of the leaves. There are light green halos around the spots. Later, the spots gradually expand or connect together to become irregular spots. The spots eventually dry up and turn dark brown, and the entire infected leaf falls off.

② Coffee Anthracnose

Coffee anthracnose is a common disease. In addition to damaging leaves, it can also attack branches and fruits, causing branch withering and fruit deadness. After the fruit is infected, the skin sticks tightly to the seed pulp, making it difficult to peel off, and in severe cases, causing fruit drop.

③ Coffee leaf spot

Also known as brown spot disease. All varieties of coffee can be infected with this disease. It is most prevalent in damp weather. It mainly harms leaves, which show irregular large spots. The spots are dark brown or black without rings. In severe cases, the leaves will fall off. Seedlings and young trees are particularly susceptible to infection, often causing wilting.

④ Coffee root rot

Also known as brown root disease, it is widely distributed but the incidence is not high . This disease harms the roots of coffee and affects the growth of the aboveground parts. The leaves gradually change from shiny green to dull yellow-green. When the disease is serious, the plant's vitality declines significantly, the leaves gradually wilt, droop and turn brown, and finally the whole plant dies. This disease is more common in Hainan Island in China.

⑤ Avoid line blight

This disease often occurs in the rainy season, and medium-grain coffee is more susceptible to infection. When infected, the back of the leaves is covered with a layer of grayish-white spider web-like mycelium. Later, these mycelium turn black, slightly brittle and a little shiny when dry, and soft and easy to peel off when wet. Mycelium can spread to branches. After the leaves are infected, they turn yellow, and finally turn black and fall off. Some fallen leaves are hung on the branches by mycelium.

(2) Main pests

① Coffee borer

These tiny black insects appear in almost all producing countries. They dig holes in the fruit and cause damage, and pesticides are difficult to repel because the coffee borers hide inside the fruit. The coffee borer has spread all over the world, originating from coffee trees in Africa in the 16th century. Columbia research shows that the coffee borer has caused great damage in the history of coffee cultivation. Coffee trees infested by borers will reduce yields because the fruits may fall before they are ripe, resulting in a reduction in harvestable fruits. Coffee borers will also damage the quality of the fruit produced by the coffee tree, thereby affecting its commercial value. If the damage is severe, the coffee will have a bitter, tarry or negative fermentation taste. Coffee damaged by borers may cause uneven roasting, which will further negatively affect the flavor.

② Coffee leaf miner

There are two main types of coffee leaf miners: the South American leaf miner Leucoptera coffeella and the African leaf miner Leucoptera caffeina. Leaf miners affect the leaves of coffee trees. Colombian coffee research shows that the larvae of leaf miners eat the leaves of coffee trees. If there are several leaf miners on a leaf at the same time, up to 90% of the structure may be necrotic. Necrosis comes from cell death, and dark water spots or brown spots will appear. Leaf fall also affects the photosynthesis of the plant. Without photosynthesis, the plant cannot grow normally, resulting in the failure of the fruit to mature and a decrease in overall yield. If these unripe or dead beans are brewed, the coffee will taste bitter and astringent.

③ Scale insects

Scale insects are insects that feed on a variety of trees and plants. They attack many parts of the coffee plant, including branches, nodes, leaves, roots and flowers. They feed on the sap of the coffee plant and secrete a sticky substance that attracts ants. This substance forms a black mold that covers the leaves and causes a reduction in photosynthesis. The sap is sucked away and the photosynthesis is reduced, which causes the coffee tree to produce lighter and unripe coffee beans, resulting in an astringent, metallic or bitter taste. Coffee scale insects are found in Africa, Australia, Asia, Central and South America.

④ Nematodes

Nematodes are small, worm-like parasites, and several species of them damage tree roots to suck sap. The nematodes form clumps on the roots, preventing the plant from properly absorbing water and nutrients. Coffee trees infected with nematodes will have fewer roots, causing the coffee tree to drop leaves and cause malnutrition, which may result in low yields and poorer quality coffee beans.

Coffee Grading

1. International mainstream grading method

Coffee grading is usually based on defect rate, bean size, altitude, green bean density, processing standards, etc. Each country's production area is different due to historical reasons, trade interests, climate and terrain and other factors. It is impossible to grade coffee beans with a unified standard or simply by altitude. It is also impossible to compare a certain grade in one country with a certain grade in another country. There are three main methods of grading coffee beans internationally:

(1) Classification by screen

The sieve grading method is to grade coffee beans by size. The size of the beans is determined by the size of the iron plate sieve with holes, and then the grade is determined. The hole size of the sieve is 1/64 inch (less than 0.4mm), so the number of the sieve represents the number of 1/64 inches. For example, the size of the sieve No. 17 is 17/64 inches, which is about 6.75mm. Therefore, the larger the number of the sieve, the larger the coffee beans.

Kenya is one of the most representative countries that uses sieve grading, and others include Tanzania, Colombia, etc. (Some countries use more than one grading method, and the examples here are representative countries that mainly use this method). Kenya's highest grade AA++ requires a sieve of No. 18 or above, which means that the bean size is more than 7.15mm. Kenya's beans are graded in detail, including AA++, AA+, AA, AB, etc. Colombia's grading is simpler, and is divided into Supremo (special selection) and Excelso (superior selection) according to the size of the beans. 80% of the beans of the special selection grade need to use a sieve of No. 17 or above, and 80% of the beans of the super selection grade need to use a sieve of No. 14/16 or above. At most, about 11% of the beans of No. 14 sieve are allowed to be mixed with the beans of No. 16 sieve. The sieves mentioned above are for flat beans. Pea Berry has its own set of sieve size standards. Generally, sieves of No. 8-12 are used to grade round beans.

(2) Classification by altitude of coffee production area

This grading standard is mainly because the quality of coffee produced at high altitudes is generally higher than that of coffee produced at low altitudes. The high altitude and low temperature make the coffee production slow, which is conducive to the accumulation of good substances. In addition, the green beans with high maturity expand well during roasting, which is conducive to roasting and the quality is more stable.

At present, the coffee producing countries that adopt this grading standard include Guatemala, Mexico, Honduras, El Salvador and other Central and South American countries. Taking Guatemala as an example, the highest grade coffee is called SHB (abbreviation of Strictly Hard Bean), which is planted at an altitude of more than 1350m, followed by HB (Hard Bean), which is planted at an altitude of 1200m-1400m, and SH (Semi Hard Bean), EPW (Extra Prime Washed), PW (Prime Washed), EGW (Extra Good Washed), and GW (Good Washed), which are planted at altitudes of 1200m, about 1000m, about 800m, 600m-800m, and below 600m. I have also talked about the grading of Guatemala on the official account before.

(3) Grading by screen and defective bean ratio

Defective beans are an important factor that destroys the final flavor of coffee. Therefore, defective beans must be removed in the last step of green bean processing. Therefore, the proportion of defective beans, supplemented by the size of the screen, is also a grading method. Due to the rise of the boutique coffee trend, coffee producing countries are paying more and more attention to the quality of coffee. Controlling defective beans is the most important way, so it is becoming more and more common to use the proportion of defective beans as a grading method or auxiliary basis.

Currently, the main representative countries that adopt the defective bean proportion method include Jamaica, Brazil, Ethiopia, etc.

The above three are the most popular coffee grading methods, but they are not all. For example, Ethiopia also uses the processing method of green coffee beans as one of the grading criteria. In addition, there is the COE rating system which is increasingly widely used. As coffee producing countries pay more and more attention to coffee quality and producers are more motivated, the grading methods of green coffee beans are not limited to the above three main methods.

2. Coffee grading standards in different countries

(1) Brazil

Brazil is the world's largest coffee producer, providing nearly 45% of the world's coffee beans. Due to the large output and many production areas, the grading work is quite troublesome and it is not suitable to adopt a single grading standard. Therefore, Brazil adopts multiple grading methods at the same time. The proportion of defective beans, screens, and cupping tests are all used in the Brazilian coffee bean grading process. Among them, the cupping test is one of the characteristics of Brazilian coffee grading. The so-called cupping test is that the coffee beans are ground into powder after roasting and soaked in hot water (about 90 degrees) to evaluate their aroma and taste. It is mainly divided into 6 levels: Strictly Soft, Soft, Softish, Hard, Rio, Rioy. The first three levels can be collectively called mild, the sweet and sour coffee is balanced, and the taste is mild. The last three have a slightly worse taste, especially the last two. The reason for the iodine taste is that the soil near Rio de Janeiro has a strong iodine smell. When the coffee falls on the ground during harvest, it will be contaminated with the odor of the adsorbed soil.

The naming method of Brazilian coffee beans is "country + production area (port) + grading name + cupping quality". For example, "Brasil Santos NY 2 SC17/18 SS FC". "Brasil Santos" means that the coffee beans come from the Santos port in Brazil; "NY2" is the defect ratio grading, NY means that it is based on the New York grading standard, and 2 is the defect ratio. The larger the number, the greater the defect ratio; "SC 17/18" indicates the size of the coffee beans, which together with the defect ratio "NY2" constitutes the grading name of the coffee beans; SS FC (Strictly Soft and Fine Cup) indicates flavor and taste, that is, cupping quality.

(2) Vietnam

The Vietnamese coffee grading method is relatively simple, and is only graded according to the size of the beans. The naming method is "country + grade name". For example, Vietnam G2 Standard Polished means Vietnamese G2 standard polished grade coffee beans.

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(3) Colombia

Colombia grades green coffee beans mainly according to their size. The naming method of green coffee beans is "country + production area + grade name + other".

(4) China

Yunnan is the main coffee producing province in China, and more than 98% of my country's coffee beans come from Yunnan. At present, there is no national coffee quality grading standard in my country. The coffee grading standard generally used by the domestic coffee industry is the industry grading standard formulated by the Yunnan Provincial Industry Association.

At present, the domestic coffee bean grading indicators mainly include particle size classification (bean mesh size), small-grain coffee defect inspection (defect ratio), color, clarity, aroma and moisture, a total of six indicators.

Coffee storage and transportation

1. Coffee storage

The surface of raw coffee beans is porous and can easily absorb odors. Improper storage and transportation can lead to quality degradation. Therefore, every link from production to trading to roasting needs to strictly control factors such as humidity, light and temperature.

The storage of general coffee beans is affected by the following four factors:

① The moisture content of the raw beans. After being picked, all coffee berries will enter wet processing, which is to peel off the outer peel and then dry the coffee beans with the inner peel, which is the parchment. Before processing, the moisture content of coffee beans is about 60%, and after processing, the moisture content of shelled coffee beans reaches 11-12%. Shelled beans are more conducive to storage and convenient for waiting for sale and transportation.

② The temperature of the storage environment. It is important to keep a constant temperature when storing green coffee beans, generally between 20 and 25 degrees Celsius.

③ Relative humidity. If the humidity in the storage environment is too high, the coffee beans will easily become moldy, while if the environment is too dry, the coffee beans will lose their flavor and aroma. According to the International Coffee Organization (ICO), the humidity standard for coffee beans during storage should be between 11% and 12.5%.

④ Is the coffee beans exposed to direct sunlight? Direct sunlight can easily cause premature aging of green coffee beans. Especially for washed beans with high moisture content in sealed bags, the rising temperature and sunlight will cause the green beans to release moisture from the surface of the beans. However, the sealed plastic bag cannot release the moisture in the bag, which will cause the coffee beans to deteriorate and mold.

Green coffee beans are usually stored and transported in the form of shelled beans. In coffee-producing areas and coffee-producing countries, parchment coffee beans (shelled coffee beans) are the main form of storage and transportation. Coffee beans stored in this form are complete coffee seeds including the seed shell, and their quality is the easiest to guarantee. However, it is impossible for coffee producers to guarantee that all coffee beans in stock can be sold out in a few months or less. In fact, the production and sales of coffee beans are a parallel and progressive process. If the market is not good, it is also common to stock up for one year and sell it the next year.

Green coffee beans can be packaged in burlap bags, vacuum plastic bags, grain woven bags, etc. Burlap bags are the most common and cheapest way to package and transport green beans. Jute is a renewable resource, and the cost of making bags is very low, and no technical requirements are required for use. However, burlap bags cannot prevent green beans from getting damp or deteriorating, and they are easily damaged by bumps during transportation and storage. Vacuum packaging plastic bags can prevent green beans from getting damp, deteriorating, and oxidizing, and they can isolate green beans from the air and prevent them from breathing. The cost of vacuum packaging is about 15-25 cents per pound (about 1 dollar for 500 grams of green beans), and vacuum equipment and personnel technical training are required. Grain woven bags can prevent coffee from getting damp and deteriorating, and are better and cheaper than vacuum packaging. Grain woven bags can store coffee longer than burlap bags, but only half the shelf life of vacuum plastic packaging. Grain woven bags cost about 5-10 cents per pound (about 50 cents for 500 grams of green beans), and it is the best choice for specialty coffee roasters.

2. Transportation of coffee

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The advantages of sea transportation are cheap and large transportation volumes. The disadvantage is that the quality of coffee beans may be damaged when exposed to high temperatures and humid environments. In addition, passing the customs inspection may delay for several weeks. If the temperature is encountered, the coffee beans are stored in a closed environment, which can easily cause water loss in a very short time and affect the quality of coffee.

Application and processing of coffee

1. First processing

In order to ensure quality and avoid secondary pollution, the picked fresh coffee fruits should be peeled and processed as much as possible on the same day (if the temperature is low, it can be left overnight and processed early the next morning). We call it primary processing or rough processing.

The initial processing methods are as follows: sun drying, water washing, Sumatra-style wet peeling, honey treatment

(1) Sun exposure method

Also known as drying method, it refers to first drying fresh coffee fruits in a sun drying yard or drying rack for 1-2 weeks to reduce the moisture to 10-12%, then use a shelling machine to remove the peel and seed coat, pick out impurities, and finally grade and packaging. The advantages of the sun drying method are that the process is simple, the investment is low, and the operation is convenient and does not rely on a large amount of water sources, but it depends more on artificial experience technology.

(2) Water washing method

Also known as wet processing method, it refers to peeling the outer skin, flesh, etc. of the flotation coffee berries using a peeling machine. Then fermenting the fermentation pond for 12-36 hours to remove the pectin stick attached to the surface of the inner skin. Then, the fermented coffee beans are cleaned and dried in a sun drying field or a ground-off drying rack to reduce the moisture content to 11%-13%, and then the remaining inner skin is removed with a shelling machine. Finally, it is graded and packaged. The water washing method requires greater capital investment and more energy, but this method helps to ensure the quality of the coffee beans and reduce damage. Most of the coffee beans in the world's coffee world now choose to use water washing to treat coffee beans.

(3) Honey treatment method

Also known as semi-washing and desalination. First remove the peel of coffee fruit and pectin with uncertain amounts, and then dry the coffee beans. The drying process is highly controllable. After drying, a small part of the pectin mucosal will remain outside the coffee beans, like honey. Depending on the residual amount of pectin, honey treatment can be divided into white honey, yellow honey, red honey and black honey treatment.

2. Deep processing

Deep processing of coffee includes fried coffee processing, instant coffee processing and flavored coffee processing.

(1) Fried coffee processing

Fried coffee processing is the process of roasting/roasting and grinding of newly processed coffee beans. Before the popularization of roasting and grinding, people usually made coffee by brewing coffee beans. Because coffee beans themselves do not exude fragrance, the coffee taste of coffee beans that are not processed is very monotonous. Compared with direct brewing coffee beans, roasting can make the coffee beans emit a stronger aroma, and the coffee oil produced during the roasting process can also make the coffee have a unique taste.

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Grinding refers to the process of grinding roasted coffee beans. The purpose of grinding is to show the flavor of coffee as comprehensively as possible. Different brewing methods require different grinding degrees. Generally speaking, the finer the coffee grinding, the easier it is to extract the substances of coffee. Grinding can be divided into coarse grinding, medium grinding, fine grinding and extremely fine grinding. Coarse grinding: The grinding degree is similar to the size of ordinary black pepper powder. Medium grinding: The grinding degree is gravel. Fine grinding: The grinding degree is as big as fine sand. Extreme grinding: The grinding degree is slightly coarse than the wheat flour.

(2) Instant coffee processing

Instant coffee refers to the dried coffee extract obtained by evaporating the moisture in the coffee extract. It can quickly dissolve in hot water, and it occupies a smaller space and volume during storage and transportation, and is more resistant to storage. However, instant coffee is produced by extracting the active ingredients from fried coffee beans and drying them. In this process, some of the aromatic substances will inevitably be lost, making the flavor and taste of the finished product not as rich and pure as that of directly fried coffee.

The production process is generally: pretreatment → roasting → grinding → extraction → concentration → drying.

Coffee beans generally contain 70% insoluble fiber, carbohydrates and 30% water-soluble substances. Extraction refers to extracting 30% of the water-soluble substances in the coffee beans. Drying is the forming process of instant coffee powder and also the process that has the greatest impact on the quality of coffee powder during processing. At present, spray drying is generally used, but because the aromatic substances of coffee are very heat sensitive, they are very easy to volatilize at a higher drying temperature (there has been a certain volatilization during the extraction and concentration process). This is the main reason why instant coffee does not have a strong aroma of fried coffee.

(3) Processing of seasoned coffee

Coffee has many different ways of drinking according to the people's sentiments and preferences in different places. At the same time, people use various additives to enhance the deliciousness of the coffee. Seasoned coffee, also known as fancy coffee, refers to coffee with seasonings and other beverages. Common fancy coffees include cappuccino, mocha, latte, etc. Seasoned coffee originated in the 1970s, when a small coffee roasting company first started selling seasoned coffee in the United States. At first, seasoned coffee was tried to replace alcohol-containing coffee, but later seasoned coffees such as tiramisu, vanilla coffee and mocha coffee gradually became popular. Commonly used additives in seasoned coffee include cardamom, cinnamon, orange peel, cocoa, mint, lemon, pineapple, brandy, etc.

Canned ready-to-drink coffee was first developed by the Japanese in 1969, thanks to the popularity of vending machines in Japan. The drink is low in acceptance in Europe and the United States, but is very popular in Asia because Asians prefer cold coffee.