How Freeze Dried Coffee Is Made

Freeze dried coffee is instant coffee and is also called soluble coffee or coffee powder. It is a beverage derived from brewed coffee beans that have been either freeze-dried or spray dried. Most instant coffee is commercially prepared by either of these methods, which can be rehydrated later. The first instant coffee was invented in 1901 by Satori Kato, a Japanese scientist working in Chicago. Some say Kato introduced the powdered substance even earlier in the early 1880s in Buffalo, New York, at the Pan-American Exposition. George Constant Louis Washington, an American inventor and businessman, developed his own instant coffee process shortly thereafter, and first marketed it commercially in 1910. The Nescaf brand, derived from Nestle and caf, was developed after seven or eight years by Max Morgenthaler. It was introduced after a more advanced coffee refining process and was launched on April 1, 1938.

High-vacuum freeze-dried coffee was developed shortly after World War II, as an indirect result of wartime research into other areas. Today, coffee beans are commercially roasted to bring out the flavor and aroma. Rotating cylinders is where beans and combustion gases are used and at 325 °F the popping sounds of roasting begin. Depending on the roast desired it takes from eight to fifteen minutes for the entire roasting process with about 25-75% efficiency. The coffee roasting process using a fluidized bed only takes from thirty seconds to four minutes; and, it operates at lower temperatures that allows greater retention of the coffee bean aroma and flavor. The beans are then finely ground by sets of scored rollers that crush the beans into.020 to 0.043 inch pieces in order to allow the coffee to be put in solution with water called extraction for the drying stage. In perculation columns at temperatures of 308° to 350 °F this concentrates the coffee solution to about 15-30% coffee by mass. The solution may be further concentrated before the drying process begins by either vacuum evaporation or freeze concentration.

This freeze-drying, also known as lyophilisation, lyophilization or cryodesiccation, is a dehydration process where coffee in this instance is frozen and then the water is removed by sublimation. Sublimation transitions a substance from the solid phase to the gas phase without passing through a liquid phase to preserve the ground coffee; it also makes coffee more convenient for transport. Freeze-drying works by freezing the ground coffee material and then reducing the surrounding pressure to allow the frozen water in the coffee to sublime; that is, to go from a solid phase to a gas phase.

Advantages of instant coffee include the speed and simplicity of preparation. Instant coffee dissolves instantly in hot water that can be boiled in 2 minutes or less in an electric tea kettle. It has a lower shipping weight per volume than beans or ground coffee to prepare the same amount and it has a much longer shelf life as long as the instant coffee is kept dry. If it is not kept dry, it will spoil.

Another advantage of instant coffee in the powder or granulated form is that it is contained in glass jars, sealed packets or tins. The user can control the strength of the coffee product, by adding more or less powder to the water, ranging from thin "coffee water" to very strong and almost syrupy coffee. Instant coffee is also convenient for putting predetermined amounts in small plastic bags for iced coffee as well as for using hot milk instead of boiling water.