All About Green Coffee Beans (Kopi Beras/Kopi Hijau)

The green coffee beans

The overall quality and chemical composition of green coffee beans are affected by many factors, such as the composition of the soil and its fertilization, the altitude and weather of the plantation, and the final cultivation and drying methods used. Coffee plants are grown in tropical and subtropical regions of central and South America, Africa, and South East Asia, mainly in regions with temperate and humid climates (Schenker 2000). Brazil is by far the largest grower and exporter of green coffee beans in the world followed by Vietnam, Colombia, Indonesia, Ethiopia and India – producing nearly 2.5 million tons of green coffee beans per year (Franca & Oliveira 2009).

The genus coffee belongs to the botanical family of Rubiaceae and comprises more than 90 different species (Davis 2001). However, only Coffea Arabica (Arabica), Coffea canephora (Robusta), and Coffea liberica are of commercial importance (Schenker 2000). Arabica accounts for approximately 64% while Robusta accounts for about 35% of the world’s production; other species with not much commercial value like Coffea liberica and Coffea excelsa represent only 1% (Rubayiza & Meurens 2005). Due to its more pronounced and finer flavour qualities, Arabica is considered to be of better quality and accordingly command higher prices (Valdenebro et al. 1999). 

Coffee cherries are harvested when they become bright-red, glossy, and firm, either by selective hand-picking or non-selective stripping of whole branches or mechanical harvesting. The hand-picking method is very time-consuming, but results in a superior product quality because only ripe cherries are selected. After harvesting, the coffee fruits are separated from the pulp, which is carried out by dry or wet processing (Clarke & Macrae 1987; Illy & Viani 1995). 

The dry process is simple and inexpensive. The whole cherries are dried under the sun in open air, followed by the separation of the hull (dried pulp and parchment) mechanically to yield the green beans. On the contrary, the wet process requires greater investment and more care, but results in a superior coffee quality. In the wet process, the pulp of the coffee cherries, which is made up of exocarp and mesocarp, is removed mechanically, but the parchment remains attached to the beans. After drying either under the sun or in a dryer, the parchment is removed to produce the green coffee beans. Bean size, color, shape, processing method, crop year, and presence of defects, are some of the parameters used to evaluate the quality of green coffee beans (Banks 2002).

Coffee cherries are harvested when they become bright-red, glossy, and firm, either by selective hand-picking or non-selective stripping of whole branches or mechanical harvesting. The hand-picking method is very time-consuming, but results in a superior product quality because only ripe cherries are selected. After harvesting, the coffee fruits are separated from the pulp, which is carried out by dry or wet processing (Clarke & Macrae 1987; Illy & Viani 1995). The dry process is simple and inexpensive. The whole cherries are dried under the sun in open air, followed by the separation of the hull (dried pulp and parchment) mechanically to yield the green beans. On the contrary, the wet process requires greater investment and more care, but results in a superior coffee quality. In the wet process, the pulp of the coffee cherries, which is made up of exocarp and mesocarp, is removed mechanically, but the parchment remains attached to the beans. After drying either under the sun or in a dryer, the parchment is removed to produce the green coffee beans. Bean size, color, shape, processing method, crop year, and presence of defects, are some of the parameters used to evaluate the quality of green coffee beans (Banks 2002). notes of the coffee blend (Parliment & Stahl 1995). Besides contributing to balanced flavour profiles, Robusta coffee is often blended with Arabica for cost reduction purpose. Robusta beans are lower in cost since the crops are more hardy to grow (more resistant to infestation) and easier to harvest (grown in regions of low elevation) than the Arabica counterpart.

Defective beans (black or brown, sour, immature, insect-damaged, split), which represent about 11-20% of coffee production, can impact the flavour of the roasted products. Mazzafera compared the chemical composition of defective beans and non-defective beans. The researcher found that non-defective beans were heavier, had higher water activity, and lower titratable acidity than the defective beans. The content of sucrose, protein, 5-caffeoylquinic acid, and soluble phenols were also higher in non-defective coffee beans (Mazzafera 1999). Nevertheless, the antioxidant level in the defective beans, especially chlorogenic acids, remains high which may be a good source of antioxidant or radical scavenger for other food applications (Nagaraju et al. 1997).

After harvesting, green coffee beans should be dried to 10-14.5% moisture content and stored below 26oC under dry environment (50-75% RH) to maintain the bean quality and to prevent the growth of mould (Gopalakrishna Rao et al. 1971; Kulaba 1981; Betancourt & Frank 1983). Under optimal storage conditions, green coffee beans may be stored for more than 3 years (Bucheli et al. 1998). Usually, green coffee beans are packaged in natural jute, sisal or burlap bags, although high quality beans may be packaged in high barrier synthetic vacuum packages fabricated from synthetic thermoplastic polymers. Cupping is a method to detect the early stages of coffee deterioration. Bucheli and others (Bucheli et al. 1996) reported that glucose was a sensitive marker for green coffee bean quality during storage. Glucose is present only in trace amount of good quality green coffee, and the content will increase when deterioration occurs (Wolfrom & Patin 1965; Bucheli et al. 1996).

Source : Physicochemical Changes of Coffee Beans During Roasting

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

 

FTIP TMIP UNPAD

fadilprojectkopi@gmail.com

Introduction KOPI!

Coffee is one of the most popular beverages in the world. Nearly 25 million farmers in 50 countries around the world depend on coffee for a significant part of their livelihoods (Cague et al. 2009). Coffee is the most traded commodity second after oil (Ponte 2002). Among coffee drinkers, the average consumption in the United States is 3.2 cups of coffee per day versus 2.6 cups in Canada (Canada 2003).

A good quality cup of coffee is depended on many factors, such as the quality of green beans, the roasting conditions, the time since the beans are roasted, and the type of water used for brewing. More than 800 volatile compounds have been identified in roasted coffee, where of around 30 compounds are responsible for the main impression of coffee aroma (Baggenstoss et al. 2008).

The overall quality and chemical composition of green coffee beans are affected by many factors, such as the composition of the soil and its fertilization, the altitude and weather of the plantation, the cultivation, and the drying methods used for the beans. Coffee plants are mainly grown in tropical and subtropical regions of central and South America, Africa and South East Asia, in temperate and humid climates at altitudes between 600 and 2500 m (Schenker 2000). The genus coffee belongs to the botanical family of Rubiaceae and comprises more than 90 different species (Davis 2001). However, only C. arabica, C. canephora, and C. liberica are of commercial importance (Schenker 2000). As a result of modem breeding techniques some hybrids of C. arabica and C. canephora have recently been introduced with success. Usually roasted coffee beans from different origins are blended at specific ratios to provide coffee of unique flavour profiles. Often time, coffee beans are blended for the purpose of cost saving.

Coffee cherries are harvested each year when they are bright-red, glossy, and firm. After removing the outer hull, the seeds inside of the cherry are commonly called "green coffee beans". The quality of the green coffee beans is dictated by a number of parameters, including bean size, color, shape, method of drying, crop year, and presence of defects (crack, withered bean, bean in parchment, mouldy bean, etc.).

The unique aroma profiles of coffee are closely related to the time-temperature profile used during roasting. The roasting profiles are chosen to produce high quality coffee which are unique to specific brands and must be strictly controlled to meet consumers’ expectations. Coffee producers rely on sensory and physicochemical characteristic evaluations to assure that roasting takes place at the target process parameters. Industrial scale roasting of coffee beans is mainly achieved by conventional drum roasting, in which beans are heated with hot gas in a horizontal drum, or vertical drums equipped with paddles. Roasting time can range from 3 to 12 min, depending on the temperature used, which is typically between 230 to 250oC. By contrast, fluidized bed roasting is achieved by directing high velocity hot air towards the beans, usually from the bottom of the roaster, to suspend the beans in turbulent air. The hot air temperature ranges from 230 to 360oC (Eggers & Pietsch 2001). The roast temperature determines both flavour formation and structural product properties. Different temperature profiles affect dehydration and the chemical reaction conditions in the bean which control gas formation, browning and flavour development. In general, the use of roasting temperature of greater than 200°C is required in order to result in desirable chemical, physical, structural, and sensorial changes in the coffee beans (Clarke & Macrae 1988; Schenker 2000; Schenker et al. 2002; Baggenstoss et al. 2008). Color change and weight loss are frequently used as a measure of the degree of roast, and both are directly related to the final roasting temperature (Sivetz 1991; Illy & Viani 1995). Other methods, such as the ratios of free amino acids (Nehring & Maier 1992), and chlorogenic acids content (Illy & Viani 1995) have also been used.

Researchers have reported the effects of time-temperature profile on coffee aroma properties. In general, low-temperature-long time roast processes result in sour, grassy, woody, and underdeveloped flavour properties. In comparison, high-temperature-short-time produced the higher quality coffee in terms of producing more aroma volatiles and higher brew yield (Schenker et al. 2002; Lyman et al. 2003). Reviewing these and other literature, one can conclude that the complex changes in coffee during roasting do not solely depend on physical parameters at the start and end point of the thermal process, but rather a path-dependent phenomenon. Therefore, to gain insight into the changes of physicochemical properties of coffee during roasting, the green beans must be roasted under controlled conditions.

Source :

Physicochemical Changes of Coffee Beans During Roasting

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

FTIP TMIP UNPAD

fadilprojectkopi@gmail.com

Akhir dari Meroasting Kopi - Degassing

After roasting, coffee beans are quenched to remove the residual heat quickly. This process can trap significant amount of CO2 in the bean, thereby lengthens the required time for CO2 degassing. This is a critical step that must be carried out before packaging of roasted coffee to prevent packaging failure due to pressure build up within the package. Conceivably, depending on the method of cooling used, post-roasting carbon dioxide degassing time may be shortened, or even eliminated. For instance, spraying roasted coffee with a controlled amount of water under agitation will remove the residual heat from the coffee beans rapidly due to the latent heat of vaporization of water. The humidified air may increase the rate of CO2 degas. Potentially, this process may be incorporated as part of the roasting regime towards the end of the roast cycle before ejecting the beans from the roaster. Alternatively, slower cooling at temperatures above ambient in an enclosed space will increase the diffusivity of CO2, potentially shortening the duration of the degassing step. Further investigation involving these types of innovative process inventions to shorten or eliminate CO2 degas will simplify the degas storage and packaging requirements of roasted coffee.

Source :

Physicochemical Changes of Coffee Beans During Roasting

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

FTIP TMIP UNPAD

fadilprojectkopi@gmail.com

Profile Roasting Untuk Kopi Arabika (Hard Bean)

Roasting Profile for Hard Bean Coffee

For hard beans, especially when roasted beyond the second crack, I recommend an “S-curve” for the roasting process. (This is based on endless cupping trials and comparison of different roast profiles). After loading the beans into the drum, the bean probe will display a drop in temperature, which will bottom out at the turning point (TP).  Hard beans will now be roasted with high initial heat. Until the start of the first crack, the heat inside the beans is endothermic; the beans are absorbing the supplied heat. Right before the start of the first crack, the heat inside the beans becomes exothermic and the beans start generating heat. At this point the operator has to reduce energy supply in order to gain control of the roast process (point I). After about two minutes of controlling the roast with low energy supply (less BTU), the operator can again increase heat (endothermic heat; the beans are again absorbing heat) to prepare for the finish of the roast. The start of energy increase can be seen at the point where the temperature curve is rising again (point A). 

During numerous cupping trials, I have found that the ideal time between the start of the first crack and the end of the roast (I and End) is at least three minutes. The ideal roast time for solid drum roasters with
convection heat (airfl ow heat passing through the drum) is 12–15 minutes. With these roasters, roast times longer than 20 minutes will produce baked flavors; roast times shorter than eight minutes will enhance sour notes. For solid drum sample roasters, the roast time can be done in 8–10 minutes. Drum roasters using infrared heat usually allow longer roasting times without affecting the quality of the roasted coffee. Fluid-bed roasting machines, which use the concept of transferring heat through a high-velocity airfl ow at a reduced temperature, usually allow faster roasting times.
 

After learning roasting the hard way—by using sight, sound and smell—I later discovered the important value of proper measuring tools, such as probes for exhaust, environmental and bean temperature. Anyone who operates a coffee roaster can replicate the experiments I’ve completed over the past years. Learning how to roast each green bean to perfection is just the fi rst step in creating that perfect cup

Source : ROAST MAGAZINE

 

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

Waktu Dan Suhu Saat Meroasting Kopi Untuk Beberapa Tipe Biji Kopi

Green Bean Types and Time Temperature Profiles

To develop an effective roast protocol, I recommend dividing green coffee beans into the following four categories:

I). Hard bean types: Roast these coffee with high initial heat and moderate heat in the final stage of the roast process. Examples: Kenya AA, Guatemala SHB and almost any coffee grown higher than 5,000 feet.

II). Medium hard bean types: Roast these coffees with moderate initial heat and moderate heat in the fi nal stage. Examples: Brazil, Sumatra, Java and most Latin American coffees grown lower then 5,000 feet.

III). Soft bean types: These coffees should be roasted with low to moderate heat during the entire process. Example: Hawaiian coffees, Caribbean types and beans grown lower than 3,500 feet.

IV). Fresh-crop coffees: These coffees normally have a bean structure that is not settled or hardened yet, especially if the coffee did not have its required resting or curing time. During the first 3–5 minutes, the operator should maintain a moderate roasting temperature, after which the roasting cycle can be continued according to the category indication that was described before. In this case, the roaster operator should attempt to obtain an almost linear roasting curve, with the internal bean temperature increasing proportionally with the roasting time. Notice the remarkable bean expansion shown in picture H. During roasting, coffee beans expand dramatically, and their volume can increase with more than 75 percent.

Source : ROAST MAGAZINE

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

Pengaruh Kadar Air dan Kerapatan Biji Kopi Terhadap Proses Roasting Kopi

How Green Coffee Quality Affects Roasting

MOISTURE CONTENT

In roasting, the moisture content of the green bean plays an important role. Under normal conditions, green coffee beans have a moisture content of 10–12 percent. The moisture content will fluctuate freely with the relative humidity content of the ambient air. In cities like Amsterdam and San Francisco, relative humidity levels throughout the year are nearly perfect for storing green beans over a length of time, and for slowing down the aging process of green coffee. This also reduces the likelihood that the roaster operator has to change roast profi les to compensate for possible variances in green coffee moisture.

The moisture inside the green beans is partially free or is present as bound moisture and contained in the carbohydrate molecules. bWe can summarize the roasting process as a three-stage cycle:

The drying phase is when the moisture content of the coffee is reduced to about two percent. During this phase, the “free” moisture—the residue of the process from cherry to green bean—evaporates. Free moisture also plays a role in the heat transfer during roasting. As soon as the beans are energized with heat, the bean’s moisture conducts this heat through out the bean. When the internal bean temperature approaches 212 degrees F or 100 degrees C., the free moisture starts evaporating. In the second phase, from the first crack to the second crack, coffee beans develop their specific aromas and flavors, which, as coffee tasters know, can produce a very complex taste profile. At the end of the second phase, all free moisture has evaporated. The length of the second phase depends on the roasting degree, which can vary from region to region and from product to product. With very dark roasts, there is also a third phase which starts when the second crack is almost completed. During this phase, carbonization takes place and the bound moisture is destroyed.

Beans with a moisture content of less than 10 percent have a sharply reduced free moisture level and will tend to roast much faster, especially in the first phase. In this case, the roaster operator needs to change the roasting profi le by initiating the roasting process at a lower heat level and by maintaining a lower amount of energy supply (less BTUs) during the first roasting phase.

Beans with a high moisture content (fresh crop coffees can have a moisture content in excess of 14 percent) often require that the roaster operator includes a pre-drying phase before starting the first phase of the process. During pre-drying, it is recommended that the roaster maintains a drum temperature of 300 degrees F or 148 degrees C. with the objective to slowly remove the excess free moisture. The actual phase one of the roasting process can begin as soon as the beans start losing their deep green color.

CELL STRUCTURE DENSITY

Lower grown beans generally have a less solid bean structure than higher grown beans. The density of the bean structure is revealed by the shape and the position of the center cut. Bean from Kenya, which was grown at an altitude of at least 5,500 feet or 1650 meters. The center cut is tightly closed and almost seems to be floating in the upper layer of the bean. In sharp contrast, Robusta bean, grown at almost sea level. In this case, the center cut is widely opened and draws like a deep crevasse through the coffee bean.

What is the relationship between bean density and roasting? High-density beans have a denser cell structure and more cells per cubic millimeter than low-density beans. As a result, high-density beans are more resistance to heat, which will be especially noticeable during the first phase of roasting. After the evaporation of free moisture, the color of the coffee beans starts changing from (light) green to yellow to light brown. During this color change, the bean starts expanding. With lowerdensity beans, the centercut will open more quickly, allowing for a faster transfer of heat, which will accelerate the process even further.

Source : ROAST MAGAZINE

JAVA PREANGER COFFEE ADDICT

Fadillah Satria

Basic of Roasting Coffee - Crack

There are two temperature thresholds called "cracks" that roasters
listen for. At about 205–207 °C, beans will emit a cracking sound. This
point is called "first crack" → bean doubles in size, becomes a light
brown color and experiences a weight loss of approximately 5%. When
the beans are at about 224–227 °C, the beans emit a "second crack."
This is the dividing point between medium and dark roasts.

Ada dua ambang batas suhu yang disebut "cracks" yang roasters dengar. 

Pada sekitar 205-207 ° C, biji kopi akan memancarkan suara retak. ini
Titik ini disebut "crack pertama" → biji kopi ganda dalam ukuran, menjadi
warna coklat dan mengalami penurunan berat sekitar 5%. kapan
kacang berada di sekitar 224-227 ° C, kacang memancarkan "celah kedua."
Ini adalah titik pemisah antara menengah dan gelap.

JAVA PREANGER COFFEE ADDICT!
Fadillah Satria