Instant coffee is a beverage derived from coffee. It first appeared in the market in 1950s. Since then, instant coffee industry has grown steadily, and has become one of the most popular kinds of coffee drunk by millions of people around the world. This coffee is so convenient and easy to use but the manufacturing process requires very expensive and complex manufacturing.
Processing instant coffee requires three steps to dehydrate brewed coffee into granules. These three steps are: pre-stripping, extracting soluble coffee solids, and drying.
Before we can extract the soluble coffee solids, the volatile compounds must be removed. This is usually done by passing steam through a bed of ground and roasted coffee.
Extracting soluble coffee solids:
Water is used as the solvent during this process. There are three ways the solids can be extracted: percolation batteries extraction, counter-current system extraction, and slurry extraction.
Percolation batteries extraction:
Coffee is held in a series of vessels. Hot water is passed through the vessels, causing the soluble coffee solids to be extracted. The extracts are later isolated from the battery and spent coffee is discharged.
Counter-current system extraction:
Coffee is placed in the bottom of an inclined cylindrical vessel and later moved upwards by the rotating of two helicoidal screws. Hot water then comes into the top, causing the extraction of coffee solids, and the solution comes out through the bottom. This process is very expensive and not suitable for small-scale processing.
Water and coffee are agitated together in a tank and separated using a centrifuge. This is also an expensive method.
There are two main drying methods used for producing instant coffee: freeze drying and spray drying.
In this process, the water in the coffee evaporates naturally and leaves behind a concentrated coffee solution. The concentrate is then slowly frozen to -40 degree Celsius, leaving behind ice crystals. Then, through sublimation (ie.liquid turning into vapour), the ice is extracted from the frozen granules. The dry grain left behind is the instant coffee. Although this methods is very time consuming, this method preserves the flavour better than the spray method.
The concentrated coffee solution left behind after natural evaporation is sprayed from a high tower into a hot-air chamber.
The circulation of hot air in the chamber removes the water in the concentrate, leaving behind dried coffee powder. Spray drying is much simpler than freeze drying. However, the use of such high temperatures in the spraying process leads to a much higher loss in coffee flavour than the freeze drying method.
If instant coffee needs to be decaffeinated, the decaffeination is carried out before the roasting process. Please visit the decaffeination (link to decaffeination document) section to learn about the various methods employed for decaffeination.
Pros and Cons
The advantages of instant coffee over regular coffee are instant coffee’s long shelf life and the simplicity of its use. The dehydrated coffee granules are rehydrated by adding hot water and are accepted by most people as delicious ‘coffee’. The major disadvantage of instant coffee is that it can be easily spoiled if not stored in an air-tight dry, container
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