THE PROCESS IN MOTION

How is instant coffee made?

Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.

▶ Play the process01Extract in countercurrent, leave the grounds behind02Keep the aromas, concentrate the extract03Atomize: the tower04Agglomerate the powder05Or freeze-dry: cold and vacuum

Extract in countercurrent, leave the grounds behind

The coffee, roasted fairly light and ground coarse to limit fines, those tiny particles that slow the flow, is loaded into a battery of five to eight columns. Water enters at 140-180 °C under pressure in the most exhausted column, passes through columns that are fresher and fresher and leaves at about 100 °C from the newest: the hottest water attacks the most emptied coffee. At these temperatures, it hydrolyzes, that is, breaks down with water, complex sugars of the cell wall that domestic brewing leaves in the grounds: the yield rises to 40-55% of the mass of coffee, against 18-22% in a cup. What is not extracted stays in the spent grounds. The extract leaves at 20-30% dry matter and is cooled immediately.

Read the stages without animation

1. Extract in countercurrent, leave the grounds behindThe coffee, roasted fairly light and ground coarse to limit fines, those tiny particles that slow the flow, is loaded into a battery of five to eight columns. Water enters at 140-180 °C under pressure in the most exhausted column, passes through columns that are fresher and fresher and leaves at about 100 °C from the newest: the hottest water attacks the most emptied coffee. At these temperatures, it hydrolyzes, that is, breaks down with water, complex sugars of the cell wall that domestic brewing leaves in the grounds: the yield rises to 40-55% of the mass of coffee, against 18-22% in a cup. What is not extracted stays in the spent grounds. The extract leaves at 20-30% dry matter and is cooled immediately.
2. Keep the aromas, concentrate the extractThe volatiles, those compounds that evaporate and that the nose perceives, are recovered before or during concentration: by steam passed through the moistened ground coffee before extraction, by condensation of grinding and roasting gases, or by pressurized extraction. Kept away from oxygen under CO₂ or nitrogen, these fractions will be reinjected at packaging. The extract is filtered and then concentrated to about 40% dry matter, by vacuum evaporation, centrifugation or freeze concentration. This is the step that separates a budget product from a branded instant coffee.
3. Atomize: the towerThe concentrated extract is sprayed in fine droplets, by a turbine or by high-pressure nozzles, at the top of a cylindrical tower twenty-five meters or more tall, in a stream of air at about 250 °C. The water evaporates in a few seconds and the powder falls to the bottom at 2-4% moisture. It is continuous, fast, the cheapest in energy; but the heat carries off volatiles, only 57% retained in the comparison cited, and cooks part of the sugars.
4. Agglomerate the powderThe atomized powder is fine, irregular, dusty. It is rewetted for a few seconds with steam or sprayed water: the grains fuse into granules, which are dried again. The product then looks like ground coffee and flows better, with no gain in aroma.
5. Or freeze-dry: cold and vacuumIn the other route, the concentrated extract is cooled to about −6 °C into a paste, frozen on belts or trays at −40 / −50 °C, then ground and sieved into granules. In a high-vacuum chamber, the ice sublimes, that is, passes directly from solid to vapor without melting, and this vapor is trapped on a condenser. The granules come out dry and porous, with 77% of the volatiles in the comparison cited; but it takes several hours per load and the highest energy of the two routes.

To remember: The taste of instant coffee is decided twice: in the deep extraction, which gives it its own bitterness, and in the drying, where the tower loses more volatiles than freeze-drying.

In history: Atomization is industrial at Nestlé in Orbe from 1938; freeze-drying arrives with Maxwell House in 1963-1964, then Nescafé Gold in 1965.

Read the full article and its sources ↓

Extraction. The coffee goes in roasted fairly light and coarsely ground, to limit fines, those tiny particles that slow the flow. It is loaded into a battery of five to eight percolation columns arranged in countercurrent, that is, the water and the coffee move in opposite directions to each other.

In practice, the water enters at 140-180 °C under pressure in the most exhausted column, the one that has almost nothing left to give. It then passes through columns that are fresher and fresher and leaves at about 100 °C in the newest. The hottest water therefore attacks the most emptied coffee, and the already loaded water ends up on the fresh coffee.

These temperatures are not only for speed. At the highest, the water hydrolyzes the polysaccharides of the cell wall: it breaks down with water complex sugars that domestic brewing leaves in the grounds. The yield thus rises to 40-55% of the mass of coffee, against 18-22% in an ordinary cup.

This is where the taste of instant coffee is decided. This extra extraction is rich in bitter compounds and caramelized sugars, and it is what gives the product its own taste. The extract leaves at 20-30% dry matter and is cooled immediately, otherwise its aromas would keep escaping. The training document sums up the principle in three steps: giant percolators, immediate cooling, then drying.

MadeHow, How instant coffee is made; US patents 5,190,779 and 5,204,136 (countercurrent extraction, 150-180 °C); professional training document, Instant coffee: atomization and freeze-drying, p. 2

Concentration and aroma recovery. The extract is filtered then concentrated to about 40% dry matter, by vacuum evaporation, by centrifugation or by freeze concentration (the water is frozen into crystals that are separated out). Before or during these steps, the volatiles are recovered: by steam stripping of the moistened ground coffee before extraction, by condensation of grinding and roasting gases, or by pressurized extraction (2,000 psi at least); these aroma fractions, protected from oxygen by CO₂ or nitrogen, are reinjected into the powder or the jar at packaging.

professional training document, Instant coffee: atomization and freeze-drying, pp. 2-3; MadeHow; Works in Progress; Ukers 1922, ch. XXXI

This is the step that separates a budget instant coffee from a branded one: without it, everything the nose perceives has left in the steam.

MadeHow, How instant coffee is made; US patents 4,701,333 and 5,242,700

Atomization (Nestlé, Orbe, 1938; principle used for milk since the 1920s). The concentrated extract is sprayed in fine droplets by a turbine or by high-pressure nozzles at the top of a cylindrical tower twenty-five meters or more tall, in a stream of air at about 250 °C; the water evaporates in a few seconds, the powder falls to the bottom at 2-4% moisture. Advantages: continuous, fast, the cheapest in energy and investment, fine powder that dissolves instantly. Drawbacks: the heat carries off the volatiles (57% retained in the comparison cited) and cooks part of the sugars; the powder is fine, irregular, dusty. Agglomeration remedies this: the powder is rewetted for a few seconds with steam or sprayed water, fuses into granules, and is re-dried; the product looks like ground coffee and flows better, with no aroma gain.

professional training document, Instant coffee: atomization and freeze-drying, pp. 2-3; MadeHow, How instant coffee is made; Works in Progress, A brief history of instant coffee

Freeze-drying (Maxwell House 1963-1964, Nescafé Gold 1965). The concentrated extract, sometimes foamed with gas to adjust density, is first cooled to about −6 °C into a paste, then frozen on belts or trays at −40 / −50 °C; the block is ground and sieved into calibrated granules, which pass into a high-vacuum chamber where the ice sublimes directly into vapor without passing through the liquid state, the vapor being trapped on a condenser; the granules come out dry and porous. Cold and vacuum are the two factors. Advantages: much better preserved aromas (77% of volatiles in the comparison cited), the structure of the coffee bean preserved to the eye, better ranking in the cup. Drawbacks: batch process, several hours per load, the highest energy consumption of the two routes, granules fragile to moisture; this is why freeze-drying is reserved for the finest and most expensive blends. The end-of-line control measurements cover moisture, density, solubility, color and, for decaffeinated instant coffee, caffeine by HPLC.

professional training document, Instant coffee: atomization and freeze-drying, p. 3; MadeHow, How instant coffee is made; ISO 20481:2008