Spray dried coffee, freeze dried coffee and liquid instant coffee are used the world over with limited appeal. But what actually is instant coffee and how are the different forms produced? The initial producion process is the same for all three, but they undergo different final processes depending on the variant required. 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. Much waste product is produced in the initial brewing chambers in the form of used coffee grounds. 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. Stage Three - The concentrated liquid coffee is then sent to the spray-drying tower where it is turned into powder.
This is achieved by pumping the coffee concentrate through an atomizer where it is broken into small droplets. The falling droplets lose their water content rapidly as they come into contact with the drying gases. They are are suspended in the drying air and typically separated by centrifugal action. The powdered coffee produced can however often be too fine to be easily used.
Consequently it often undergoes an additional process called agglomeration, which results in a more useable and appealing product. The fine coffee particles are gathered into larger particles using a partial re-hydration process which produces a more visually tempting finished product somewhere between the consistency of powder and freeze dried coffee. Spray dried coffee is considerably cheaper to produce that freeze dried coffee, the latter of which is considered the more higher quality product.
For more information about coffee and coffee brewing equipment visit http://www.cafebar.co.uk