Processing instant coffee is still quite unfamiliar to many farmers who have long been used to brewing coffee with a traditional drip filter. This article helps them understand that using instant coffee is not only a technological advancement in coffee processing, but also provides a beverage that ensures the highest standards of food safety.
Technological Process for Producing Instant Coffee
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After roasting, green coffee beans are ground either to make drip-brew coffee or to be further processed into instant coffee.
The production of instant coffee from roasted coffee powder involves the following stages:
Extraction
The purpose of extraction is to draw the soluble compounds from the roasted coffee grounds into water. Hot water at 80–90 °C is used for extraction. Water at higher temperatures is avoided, as it may extract undesirable substances.
The coffee grounds for instant coffee should have a relatively coarse grind size, and multiple extraction cycles are carried out to limit fine particles from dissolving too deeply into the water.
A typical batch extractor is a tower filled with roasted coffee grounds and maintained at the required temperature. Hot water is pumped from the bottom upward through the column of coffee grounds. During this process, the soluble compounds are extracted and the coffee solution is collected at the top.
To increase the concentration of the extract, the coffee grounds in the towers are replaced sequentially so that the liquid passing through each tower becomes progressively richer in soluble compounds. To prevent dry pockets, the coffee grounds are pre-moistened with saturated steam before hot water is introduced. The concentration of the coffee extract can reach 20–22%.
Concentration
After extraction, the coffee extract has a concentration of about 20–22%, which is not yet suitable for drying. The solution is therefore concentrated to about 30–33% for easier drying.
This is typically done by vacuum concentration:
The coffee extract is pumped into a heating device where the water is evaporated. A vacuum created by a barometric system draws off the water vapor, which then condenses in a cooling chamber. The process continues until the desired concentration is reached.
Drying
Drying converts the concentrated coffee extract into a dry powder for convenient storage and use.
The common method is spray drying:
The concentrated coffee extract is pumped to the top of a cyclone dryer where it is dispersed into a fine mist by a rapidly spinning perforated disk. Hot, dry air is blown into the cyclone, quickly drying the mist into fine coffee powder. The instant coffee powder is collected at the bottom of the cyclone and typically has a moisture content of only 1–2% and a deep dark brown color.
Aroma Recovery
If coffee powder is processed directly, much of its natural aroma would be lost, especially during spray drying. Therefore, the coffee’s aromatic compounds are first captured and later added back to the instant coffee powder.
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Desorption (Aroma Stripping):
This is carried out in a vertical column using an inert gas, typically nitrogen (N₂). The roasted coffee powder is heated in the column to release its aromatic compounds. Hot nitrogen gas (about 95 °C) is pumped in from the bottom. A suction fan at the top draws out the nitrogen–aroma mixture while maintaining a slight vacuum to facilitate desorption. -
Adsorption (Aroma Reabsorption):
After spray drying, the instant coffee powder—now very porous and with 1–2% moisture—is passed through another vertical column. The nitrogen–aroma mixture is cooled to about 8–9 °C and then flows through the dried coffee powder, which reabsorbs the aromatic compounds.
The result is a finished instant coffee powder that retains much of the natural aroma of freshly roasted coffee.