Instant coffee is a beverage derived from roasted coffee. It first appeared on the market in the 1950s. Since then, it has grown rapidly to become one of the most popular forms of coffee, enjoyed by millions of people around the world.
This type of coffee is very convenient to use, but the process of making it requires complex and costly technology.
Processing Steps
Table of Contents
Producing instant coffee involves three main steps to remove water and turn brewed coffee into small granules: pre-stripping, extraction of soluble coffee solids, and drying.
1. Pre-stripping
Before extracting the soluble solids, the volatile aromatic compounds must first be captured. This is usually done by passing steam through the freshly roasted and ground coffee.
2. Extraction of Soluble Coffee Solids
At this stage, water acts as the solvent. The soluble solids can be extracted in three different ways:
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Percolation batteries:
Ground coffee is held in a system of columns. Hot water is passed through the columns to dissolve the soluble compounds. The extract is collected, while the spent grounds are discharged. -
Counter-current system:
Coffee is fed into an inclined trough and moved upward by two fast-rotating screws. Hot water is introduced at the upper end, washing the soluble solids downward so the coffee extract can be drawn off at the lower end. This method is expensive and not suitable for small-scale production. -
Slurry extraction:
Ground coffee and water are mixed together in a large tank, then separated using a centrifugal pump. This method is also relatively costly.
3. Drying
The extracted coffee liquor must then be dried to form the final instant coffee powder or granules. Two main drying methods are used:
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Freeze drying:
The coffee extract is first concentrated to a high-strength solution and then frozen to about –40 °C to form ice crystals. Through sublimation (where ice turns directly to vapor), the ice is removed, leaving dry coffee granules. Although more time-consuming, freeze drying preserves the aroma and flavor far better than spray drying. -
Spray drying:
After concentrating the coffee extract, it is sprayed from the top of a tall drying tower into a stream of hot, dry air. The hot air instantly removes the water, leaving dry coffee powder at the bottom. This method is simpler and cheaper but the high temperature causes more loss of coffee aroma.
If decaffeinated instant coffee is desired, the caffeine must be removed before the roasting stage.
Key Advantages and Drawbacks
Instant coffee keeps well in storage and is extremely convenient: when hot water is added, the dehydrated coffee instantly re-hydrates into a ready-to-drink beverage that many people consider pleasantly flavorful.
Its main drawback is that, unless kept in a dry, airtight environment, it can easily spoil or lose quality when exposed to moisture or air.