Processing of instant coffee

Instant coffee entails the extraction of ground coffee with warm water to form a concentrated liquid brew, followed by removal of the water from the brew by some method of dehydration. The residue which is left is instant coffee.

Instant coffee is produced after grinding and extraction by percolation. Instant coffee is prepared in either of the following way:
*By forcing an atomized spray of very strong coffee extract through a jet of hot air. This evaporates the water in the extract and leaves dried coffee particles, which are packaged as instant, or soluble, coffee. Most spray-dried instant coffees have been marketed in a granular form, rather than the small special spray-dried form, since the mid-1960s.

*By freeze-drying, which results in a product that looks somewhat like ground roasted coffee and retains some of coffee’s aroma. Freeze dried coffee has a longer shelf life than spray-dried coffee.

Spray and freeze fried coffee extract have generally lost their original volatile flavor and aroma compounds. The flavor of instant coffee can be enhanced by recovering and returning to the extract or finished dry products some of the natural aroma lost in processing.

The aroma constituents from the grinders, percolation vents and evaporators may be added directly or in concentrated or fractioned form to achieve the desirable product attributes.
Processing of instant coffee 

Coffee processing of decaffeination

Caffeine is a physiologically active component in coffee, was been studied intensively. The process of decaffeinating coffee began at the turn of the last century, in Germany.

Decaffeinated coffee means in the EU countries a maximum caffeine concentration of 0.1% related to the dry mass; in the US, it means less than 3% of the amount initially present in the beans.

Today there are only three primary decaffeination methods used by the coffee industry.

*The Swiss water process or water only method
Swiss water decaffeination almost always uses high quality arabica beans. This process does not use chemicals.

In this process method the green coffee beans are soaked in water for several hours, which removes about 97 percent of the caffeine as well as a few of the flavor components.

*The water decaffeinated method 
The method was first mentioned in 1941 by Berry and Walters. It uses green coffee extract with equilibrium quantities of non-caffeine soluble solids and removal of caffeine from the extract with dichloromethane on liquid-liquid extraction.

In water decaffeination process, sometimes chemicals rather than charcoals filters, are used to extract the caffeine. In this process, no solvent touches the beans. After the beans are steamed, they are soaked in water in big vats, which removes the caffeine along with all the soluble solids in the beans.

*The solvent method
Certain solvents, such as methylene chloride and common ethyl acetate, are the most widely used chemical compounds to decaffeinate coffee.

A raw green beam is softened with steam and water allowing bean to double in size. The beans are vibrated for about an hour in the solvent, which loosens the caffeine and combines it with the chlorine.

The commercial decaffeination process is at present carried out on the green coffee beans before roasting.
Coffee processing of decaffeination

Coffee process of roasting

Green beans smell green earthy, so they must be heat treated in a process called roasting to bring about their truly delightful aroma.

Coffee beans are usually roasted in large batch dryers which spin and heat them evenly at temperatures that reach 550° F. In the USA continuous roasting of beans is the common method, using fluidization of beans in a perforated cylinder with a horizontal airstream.

The process consists of roughly three stages lasting about six minutes altogether: begin roasting, end roasting, quenching. During roasting heat is transferred by contact of the beans with the walls of the roasting apparatus or by hot air or combusted gases.

The bean is warmed intensely to drive off free and bound moisture which constitute about 12% of initial weight. During the roasting process, about 20 percent of the water content of the green beans evaporates and carbon dioxide escaped. They are accompanied by some carbon monoxide and organic volatiles.

The bean’s starch content is converted to sugar. The volatiles oils and acids that gave coffee its tempting aroma and delicious flavor are developed during the roasting process.

The roasting process is terminated at the desired flavor, indicated by the darkness of color.

When the desired degree of roast is reached, the beans have to be cooled down rapidly by water quenching or cold air in order to stop further changes in color, flavor and volume. Normally the product is discharged into an air cooler for rapid cooling to 104° F.
Coffee process of roasting

Coffee roasting

Roasting brings raw, green coffee beans to a state called pyrolysis, which generally occurs at from 400 ° F to 420° F (204 ° C to 216 ° C) and liberates about 150 to 200 BTUs of heat. The beans are roasted to a light color for 3-10 minutes which weight loss 14 – 17%.

At 212° F the coffee beans turn yellow and lose water, from 248° F to 302 ° F the color changes from yellow to light brown and russet, folds in the beans open and release an essential oils, cafeone. At 392° F pyrogenation is reached.

The loss in weight by roasting depended on the kind of the coffee and the manner in which the roasting was done.

During roasting, vapors formed and cell fragments are removed by suction of an exhauster and in larger plants, incinerated.

Until coffee is roasted, its taste remains unknown. The end product is discharged rapidly to cooling sifters or is sprinkled with water in order to avoid over-roasting or burning and aroma loss.

The cooling was then followed by an air suction operation called ‘stoning’ which removed any stones or other hard material that would damage a grinding mill.

By the time coffee finishes roasting, more than 700 identified compounds cumulatively called coffee flavor – exist.

The most obvious change was production of a fragrance, attributed to a mixture do several substance. It was partly due to the volatile oil called caffeol, which was produced at the expense of other substances and partly to the sugars which were caramelized.
Coffee roasting

Blending of coffee

The blending of coffees is an art. Each blend is the official signature of the inspired coffee roaster.

Bean blends combine the best qualities of one single origin with the different but complementary qualities of another, resulting in a unique, signature taste.

The ability to balance the elements of the blend, so that no two types of coffees that are combined posses similar characteristics, is a principal skill for such artisans. Blending requires the expert skill of knowing each ingredient coffee, having in mind clear cup profile as the goal, and knowing how to achieve it.

In a perfect blend, the result is greater than the individual parts, causing a third unique flavor to emerge. Blending experts typically combine no more than three different coffees. Blending may be done before or after roasting.

Blending before roasting is traditionally used by retail and institutional roaster.

Blanding of coffees is used to create classis coffee mixtures to make lower cost versions of high-priced coffees, and to produce commercial products that remain consistent in taste and price even as crops vary and prices rise and fall.  
Blending of coffee

Coffee beans processing

Four methods of industrial processing of green coffee beans are used:
*Roasting, an essential process to develop coffee’s aromatic properties. Roasting changes the appearance, consistency, smell, flavor and composition of the coffee. Roasting coffee beans causes the bean to expand and become more dense, and brings out the natural oils found inside.

*Grinding
When broken down by grinding, coffee cells release their content of pyrolytic gas formed at roasting. This gas is mostly composed of CO2 and CO, accompanied by small amounts of hundreds of volatile chemical species.

The volatiles only present in low concentrations but are essential bringing forth the typical coffee aroma.

*Percolation followed by dehydration to obtain soluble coffee. In percolation process, more coffee beans are used, with a shorter percolation time. This give a strong flavor but avoids the bitterness.

Percolation refers to the coffee making process in which crushed coffee beans are broken up, mixed together, brought into collision and recomposed in a percolator to extract the full flavor of the coffee.

*Decaffeination
Caffeine is removed by soaking the beans on water or by using solvents or carbon dioxide. The last is thought to be the best method as it does not affect the flavor and there is no residue.

Prior to processing, green coffee beans are cleaned and dusted by pneumatic separating machines, then stored in partitioned soils.

Harvested coffee beans begin to ferment almost immediately and if the crop is not to be lost, it must be processed within 8 to 36 hours after picking.

Processing must remove the seeds of the coffee berry – the source of coffee as a beverage – from the surrounding organic material.
Coffee beans processing

Coffee Harvesting

Coffee Harvesting
Coffee harvesting may have different objective depending in the method of processing as well as the availability and cost of labor.

Where the wet or semi-dry method is to be used, traditionally the main objective is to maximize the percentage of ripe cherries harvested.

On the other hand, if the dry method is to be used, the usual objective is to harvest all cherries simultaneously with the least percentage of unripe ones.

The ideal situation is to harvest all fresh, ripe cherries with the least possible damage to the tree, irrespective of the processing system to be used.

With the harvesting technology available today, 100% ripe cherry harvesting may be only achieved be selective hand-picking, which generally corresponds to the most expensive operation available.

In situations where labor is scarce or expensive in relation to coffee prices, selection may have to be overlooked so unripe and over-ripe cherries must then be picked. This is mostly the case today, with 100% ripe cherries harvesting nearly impossible to achieve with or without selective picking.

High quality coffee may still be produced in any case from the fresh, ripe cherries alone, but the total volume of high quality coffee available is then smaller.

Ideally, only ripe coffee berries should be harvested because they provided the best beverage. In Brazil, 90% of the plantation are harvested manually; the berries are stripes from the plant branches and fall on the ground, into basket or on fabric or plastic strips laid under the plant. Letting the berries fall on the ground is not recommended because dirt, debris, moldy and rotten berries end up being collected as well.

However, mechanical harvesting has been increasingly used it is so difficult to hire manage and pay the large force required for manual harvesting; operational, costs may drop by 40%. Mechanical harvesting is more suitable for medium to large plantation in areas with slopes of up to 20% incline.
Coffee Harvesting