Freeze-drying Instant Coffee |
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Freeze-drying Instant Coffee |
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A far better method of production is
that of freeze-drying, as the coffee is not subjected to the
harshness of steam heat. The process is much slower, and therefore
more expensive on a commercial level. A strong coffee extract is
made and poured onto a shallow trough, where it is frozen. It then
passes very slowly through a vacuum chamber where sublimation
occurs: the temperature is slightly raised as the air pressure is
lowered: before the frozen extract, now in the form of ice crystals,
can return to a liquid state, it is absorbed into the vacuum,
leaving behind only the coffee-flavor substances which, when the ice
is gone, are in the form of the freeze-dried particles. Again,
coffee aroma is sprayed into the top of each jar before it is
sealed. Because the freeze-drying process is gentler and destroys less of the original coffee flavor, most coffee companies have found it worthwhile to use a better grade of beans from which to make the extract, and while this, too, raises the price over that of powder or granules, it also ensures a better cup of instant coffee. |
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