There are several methods of manufacturing instant coffee. I have
included the methods here, as well as links to the entire process.
Instant coffee was invented by a scientist named George C.
Washington, in 1906. (Further down in my answer, this is disputed by
another site, claiming a different inventor!)
?He was an Englishman living in Guatemala and a chemist by trade. An
avid coffee-drinker, he noticed a powdery buildup on the spout of his
favorite silver coffee pot. That prompted his curiosity and further
experimentation followed. He eventually produced a dried coffee
crystal much like we still have today. His brand was called Red E
?There are two methods for producing instant coffee crystals:
freeze-drying and spray-drying. The freeze-drying method preserved the
most 'coffee flavour' but it's a more involved procedure. First, the
coffee is allowed to sit so the water evaporates naturally, leaving a
concentrated coffee solution. This concentrate is then frozen to
around -40 Celsius. The remaining water freezes into ice crystals.
Sublimation (a natural process similar to evaporation) is used to
remove the ice. What's left is dry grains of coffee.
The second method is spray-drying. The water is again allowed to
evaporate, forming a concentrate. The concentrated coffee is sprayed
from a high tower in a large hot-air chamber. As the droplets fall,
the remaining water evaporates. Dry crystals of coffee fall to the
bottom of the chamber. The high temperatures involved in this method
do tend to effect the oils of the coffee and more flavour is lost.?
?The Freeze Drying Process
1.Agglomerated wet coffee granules are frozen. For instant coffee this
is a very important stage. Freezing too fast leads to large ice
crystals and a very porous product and can also affect the colour of
the coffee granules.
2.Frozen coffee is placed in the drying chamber, often on metal trays.
3.A vacuum is created within the chamber. The strength of the vacuum
is critical in the speed of the drying and therefore the quality of
the product. Care must be taken to produce a vacuum of suitable
4.The drying chamber is warmed, most commonly by radiation but
conduction is used some plants and convection has been proposed in
some small pilot plants. A possible problem with convection is uneven
drying rates within the chamber, which would give an inferior product.
5.Condensation - the previously frozen water in the coffee granules
expands to 107 its volume, the removal of this water vapour from the
chamber is vitally important, making the condenser the most critical
and expensive components in a freeze drying plant.
6.The freeze dried granules are removed from the chamber and packaged.
This site contradicts the site above in saying that instant coffee was
first invented by Sartori Kato, in 1901, by a Japanese scientist
working in Chicago. Its possible that each person developed a process
for making instant coffee, independent of the other.
?Spray drying is the most economic method of producing soluble coffee.
The feed to the spray dryer is a mixture of concentrated aroma and
hydrolysed fractions, with the preserved aroma components added. In
order to maximize aroma retension, drying of the extract takes place
under conditions that maintain low powder temperatures. Different
types of spray dryers can be used for drying of cofee. Bulk density
and colour control is possible by means of in-line gas mixers. Inert
gas is injected into the feed system just prior to the nozzle atomizer
used in the spray drying system.
In cases where spray dried powders require further agglomeration, an
additional process stage is used involving powder wetting, afterdrying
and cooling. Control of weeting is carried out with water and/or
saturated steam in an agglomeration chamber equipped with a rotating
impacter. The agglomerates are then dryed and cooled in the attached
fluid bed, followed by sieving and packing. Fines and oversize
fractions are reprocessed within the agglomeration plant.?
"The production of instant coffee is unsuitable for small-scale
enterprises as it requires very expensive machinery eg an extractor
and a freeze or spray drier. A report by the Natural Resource
Institute (NRI) states that the smallest economically viable instant
coffee factory is 1000 tons/year in India. Various people are trying
to design machinery suitable for small-scale production of instant
coffee which may be able to reduce the throughput necessary for
economic viability. To produce an instant coffee, the soluble coffee
solid and volatile compounds have to be extracted and then dried into
a powder or granules.? Page 4-7 describes the entire process:
?Most recently the process of lyophilization or ?freeze-drying? has
become the standard method of making instant coffee. This method is a
vast improvement over other methods for two reasons. The first is that
the coffee concentrate is extracted under high pressure so the water
used never actually boils even though the water is well above the
The second is that the water is removed without adding heat which
helps preserve the coffee flavor. The concentrate is then frozen and
placed in a vacuum chamber and the temperature is raised to just above
freezing, at which point one would expect the mixture to melt.
However, since it is in a vacuum the frozen water is prevented from
becoming a liquid. But since the temperature is above freezing the
solid water (ice) goes directly from a solid to a vapor. It is then
vented to a separate chamber where it is refrozen as pure water. What
is left in the vacuum chamber is the coffee residue.?
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