Whether you agree with the ads that freeze dried instant coffee packs in more flavor, or stand by the powdered brand you’ve been using for years, the manufacturing process for both is similar, at least until the final step.
When coffee arrives at a factory that will turn it into instant, it already looks like the ground coffee available in your supermarket. The green beans have been roasted to the appropriate color required by each brand, blended for that particular Maxwell House or Yuban flavor, and ground.
The factory staff then actually percolates huge amounts of coffee. Whereas you might put 4 tablespoons into your percolator, one factory may brew 1,800 to 2,000 pounds at a time.
The coffee then passes through tubes in which high pressure and temperature cause some water to evaporate, leaving behind coffee with a very high concentration of solids. This liquid, known as coffee liquor, is then ready to be dried by one of two methods.
Powdered instant coffee is dried by heat, which some people feel is detrimental to the flavor. The liquor is poured through a large cylindrical drier, roughly 100 feet high and 60 feet across, and is heated to 500 degrees Fahrenheit; by the time the liquor reaches the bottom, the water has evaporated, leaving powdered instant coffee, ready to be collected and packed into jars.
By the freeze drying method, the coffee liquor is frozen into blocks, which then are broken into granules of the desired size.
The granules are then put into a vacuum drier, a box kept in a continuous vacuum, which dries the coffee through sublimation, that is, the frozen water changes directly into vapor, which is in turn removed through valves. High temperatures that might damage the flavor are not required, since the granules are in a vacuum (the thinner the atmosphere, the lower the temperature at which water boils).
What remains after vacuum drying are coffee solids that dissolve instantly in hot water for a quick cup of coffee.