Instant coffee, also called soluble coffee and coffee powder, is a beverage derived from
brewed coffee beans. Instant coffee is commercially prepared by either freeze-drying or spray
drying, after which it can be rehydrated. Instant coffee in a concentrated liquid form
is also manufactured. Advantages of instant coffee include speed
of preparation, lower shipping weight and volume than beans or ground coffee, and long
shelf life — though instant coffee can spoil if not kept dry.
History
Instant or soluble coffee was invented and patented in 1890, by David Strang of Invercargill,
New Zealand, under patent number 3518. It was sold under the trading name Strang's Coffee
citing the patented "Dry Hot-Air" process. The invention was previously attributed to
Satori Kato, a Japanese scientist working in Chicago in 1901. Kato introduced the powdered
substance in Buffalo, New York, at the Pan-American Exposition. George Constant Louis Washington
developed his own instant coffee process shortly thereafter, and first marketed it commercially.
The Nescafé brand, which introduced a more advanced coffee refining process, was launched
in 1938. High-vacuum freeze-dried coffee was developed
shortly after World War II, as an indirect result of wartime research into other areas.
The National Research Corporation was formed in Massachusetts as a process-development
company employing high-vacuum technology. It developed high-vacuum processes to produce
penicillin, blood plasma and streptomycin for US military use. As the war ended, NRC
looked to adapt its processes for peacetime uses. It formed Florida Foods Corporation
to produce concentrated orange juice powder, and originally sold its product to the United
States Army. That company later changed its name to Minute Maid.
These days examples of popular instant coffee brands are Nescafe, International Roast, Extra,
Folgers, Maxwell House, Robert Timms, Starbucks VIA and Kava.
Use
Instant coffee is available in powder or granulated form contained in glass jars, sachets or tins.
The user controls the strength of the resulting product, by adding more or less powder to
the water, ranging from thin "coffee water" to very strong and almost syrupy coffee. A
novel way is to use coffee bags, similar to tea bags.
Instant coffee is also convenient for preparing iced coffee like the Greek frappé, which
is popular in warmer climates and hot seasons. In some countries, such as Portugal, Spain
and India, instant coffee is commonly mixed with hot milk instead of boiling water. In
other countries, such as South Korea, instant coffee commonly comes pre-mixed with non-dairy
creamer and sugar and is called "coffee mix". Said to have been popularised in the UK by
GIs during World War II, instant coffee still accounts for over 75 percent of coffee bought
to drink in British homes, as opposed to well under 10 percent in the U.S. and France and
one percent in Italy. Production
As with regular coffee, the green coffee bean itself is first roasted to bring out flavour
and aroma. Rotating cylinders containing the green beans and hot combustion gases are used
in most roasting plants. When the bean temperature reaches 165 °C the roasting begins, accompanied
by a popping sound similar to that produced by popcorn. These batch cylinders take about
8–15 minutes to complete roasting with about 25–75% efficiency. Coffee roasting using
a fluidized bed only takes from thirty seconds to four minutes, and it operates at lower
temperatures which allows greater retention of the coffee bean aroma and flavor.
The beans are then ground finely. Grinding reduces the beans to 0.5–1.1-millimetre
pieces in order to allow the coffee to be put in solution with water for the drying
stage. Sets of scored rollers designed to crush rather than cut the bean are used.
Once roasted and ground, the coffee is dissolved in water. This stage is called extraction.
Water is added in 5–10 percolation columns at temperatures of 155 to 180 °C; this concentrates
the coffee solution to about 15–30% coffee by mass. After filtration, this may be further
concentrated before the drying process begins by either vacuum evaporation or freeze concentration.
Freeze drying
The basic principle of freeze drying is the removal of water by sublimation.
Since the mass production of instant coffee began in post-WWII America, freeze-drying
has grown in popularity to become a common method. Although it is sometimes more expensive,
it generally results in a higher-quality product. Agglomerated wet coffee granules are rapidly
frozen. Frozen coffee is placed in the drying chamber,
often on metal trays. 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 strength.
The drying chamber is warmed, most commonly by radiation but conduction is used in 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. Condensation — the previously frozen water
in the coffee granules expands to ten times its previous volume. The removal of this water
vapor from the chamber is vitally important, making the condenser the most critical and
expensive component in a freeze-drying plant. The freeze-dried granules are removed from
the chamber and packaged. Spray drying
Spray drying is preferred to freeze drying in some cases because of its economy, shorter
drying times, usefulness when dealing with such a heat-sensitive product, and the fine,
rounded particles it produces. Spray drying produces spherical particles
about 300 micrometres size with a density of 0.22 g/cm³. To achieve this, nozzle atomization
is used. Various ways of nozzle atomization can be used each having its own advantages
and disadvantages. High speed rotating wheels operating at speeds of about 20,000 rpm are
able to process up to 60,000 pounds of solution per hour. The use of spray wheels requires
that the drying towers have a wide radius to avoid the atomized droplets collecting
onto the drying chamber walls. Completed in 5–30 seconds.
Moisture content change: IN = 75-85% OUT = 3-3.5% Air temperature: IN = 270 °C OUT = 110 °C
One drawback with spray drying is that the particles it produces are too fine to be used
effectively by the consumer; they must first be either steam-fused in towers similar to
spray dryers or by belt agglomeration to produce particles of suitable size.
Decaffeination
In commercial processes, the decaffeination of instant coffee almost always happens before
the critical roasting process which will determine the coffee's flavour and aroma processes.
Composition The caffeine content of instant coffee is
generally less than that of brewed coffee. One study comparing various home-prepared
samples came to the result that regular instant coffee has a median caffeine content of 66 mg
per cup, with a median cup size of 225 ml and a caffeine concentration of 328 µg/ml.
In comparison, drip or filter coffee was estimated to have a median caffeine content of 112 mg,
with a median concentration of 621 µg/ml for the same cup size.
Regarding antioxidants, the polyphenol content of a 180 ml cup of instant coffee has been
estimated to be approximately 320 mg, compared to approximately 400 mg in a cup of brewed
coffee of the same size. Health effects
Instant coffee appears to be as efficient as regular drip brew coffee in decreasing
the risk of diabetes type 2. On the other hand, it has been associated with an increased
risk of bladder cancer in women when compared to regular coffee, whereas for men both instant
and regular coffee have been associated with an increased bladder cancer risk. However,
current review research suggests that there is no dose-response relationship between coffee
drinking and bladder cancer, and that previous studies may have been confounded by unidentified
risks of bladder cancer. Instant coffee decreases intestinal iron absorption
more than drip coffee. One study estimated that, when a cup of instant coffee was ingested
with a meal composed of semipurified ingredients, intestinal absorption was reduced from 5.88%
to 0.97%, compared to an absorption of 1.64% with drip coffee. It was also estimated that,
when the strength of the instant coffee was doubled, intestinal iron absorption fell to
0.53%. Apparently, however, there is no decrease in iron absorption when instant coffee is
consumed 1 hour before a meal, but the same degree of inhibition as with simultaneous
ingestion occurs when instant coffee is taken 1 hour after a meal.
Animal experiments have indicated that instant coffee confers no risk related to reproduction,
lactation, embryotoxicity or teratogenicity, but possibly a risk of a delay in bone calcification
in high doses. Brewed instant coffee contains a similar level
of acrylamide compared to drip brewed coffee. Regulatory context
In the EU, regulations include the following details:
Species of coffee bean Geographical origin
Processing detail Year of crop
Solvents used in decaffeination Caffeine level
Various institutions govern the coffee industry and help to achieve standardisation and also
release information to the public. International Coffee Organisation
Codex Alimentarius Commission of the UN National Coffee Association
Non-food use Instant coffee is one of the ingredients in
"Caffenol-C", a home-made, non-toxic black-and-white photographic developer. The other ingredients
in the basic formula are ascorbic acid and anhydrous sodium carbonate; some recipes also
include potassium bromide as a fog-reducing agent. The active ingredient appears to be
caffeic acid. Initial experiments on Caffenol were performed in 1995 at the Rochester Institute
of Technology; addition of ascorbic acid began around 2000, yielding the improved Caffenol-C,
which is less likely to stain negatives than the original formulation. Experiments have
shown that cheaper, less desirable brands of coffee work better for this application
than more expensive brands. See also
Instant breakfast Instant soup
List of dried foods Powdered milk
References
Bibliography Romualdo Verzosa Jr., ed.. Encyclopedia of
Chemical Technology, volume 6. John Wiley & Sons. ISBN 0-471-52674-6.
Masters, K. Spray Drying Handbook. Longman Scientific & Technical. ISBN 0-582-06266-7.
John J. McKetta, ed.. Encyclopedia of Chemical Processing and Design. Marcel Dekker Inc.
ISBN 0-8247-2604-9. External links
How Instant Coffee is Made from Madehow.com