What is Spray Dried Coffee?
Instant coffee comes in three different forms, freeze dried, spray dried and liquid concentrate. Although the initial brewing process is the same for all methods they vary greatly with the methods used to produce the final coffee product.
Typically the coffee beans chosen for instant coffee production are from the lower end of the quality scale, since many of the subtle flavours and aromas of the more expensive types are lost in the production process.
Freeze dried coffee was discussed in a different article, so here we concentrate on the production of Spray Dried Coffee.
Stage One - This stage involves the production of large quantities of freshly brewed coffee using industrial bulk brewers. Freshly ground coffee is put into contact with hot water in industrial brewers until the desired degree of extraction has occurred. The process can either be the drip filter method that many use in the home or an industrial version of the coffee percolator. A large quality of waste material in the form of used coffee grounds are produced by these methods. However these days they are recycled for use in animal foods, used as organic fuels or processed as compost.
Stage Two - The resulting coffee liquor liquid is then concentrated through an evaporation process where some of the volatile aroma components are removed and stored to be returned later prior to packing.
This stage produces a thick more viscous coffee liquid that is then ready for the next stage in the making of spray dried instant coffee.
The ice crystals that formed in the freezing process from the water content in the beverage are then removed in a process called sublimation. Here the frozen granules are subjected to a high vacuum which results in much of the water ice content to be transformed directly into gas (without a liquid stage it would normally undergo) before being returned to room temperature.
The resulting freeze dried coffee typically contains just 3 to 5 percent water. The more volatile flavour and aroma compounds extracted at the initial brewing stage are then returned to the dried product just before packing.
As you can imagine an industrial factory producing freeze dried coffee produces vast amounts of used coffee grounds in the production process, but these are not put to waste. They are usually sold on as animal feed, compost or organic fuel.
It should be noted that freeze dried coffee is different from spray dried coffee and is generally accepted as superior in quality. The spray dried production of coffee will be the subject of another article.
For more information about coffee and coffee brewing equipment visit http://www.cafebar.co.uk