INSTANT COFFEE CLEANING AND BLENDING The first step in the processing line is a thorough cleaning of the green coffee beans, to remove defective beans and extraneous matter. Blending is usually carried out to achieve optimum flavour development in the roasting stage ROASTINGAND GRINDING Roasting enhances the flavour and aroma and may be carried out batch-wise orcontinuously. The lattercontinuous method is more cost effective. Grinding to a particle size most suitable for the extraction process follows EXTRACTION This is either continuous or batch. The continuous method employs a tiltable jacketed pressure vessel containing two helicoidal conveyors. Hot water enters the top end and the extract flows through the trough by gravity. The dwell time is from 30 to 40 minutes. In two stage extraction, atmospheric ressure is used in the first stage and pressure Batch extraction is carried out in a counter-current column battery unit featuring split extraction under closely controlled conditions, and yields of over 48 percent can be achieved. The first stage produces a prime quality extract, which is held separately pending final pretreatment and drying. The second stage produces a high overall extract yield but with low solids and this has to be subsequently concentrate CONCENTRATION recovery section, or arotary thins stage falling fiImevaporatorwitharoma evaporator designed uniquely by niro for heat sensitive products Both types of evaporator operate under vacuum, thereby maintaining low extract temperatures SPRAY DRYING The concentrated extract is pumped to the pressure nozzle in the dryin chamber where it is atomized and contacted with hot air Drying temperatures are low in order to preserve aroma and flavour in the dry product. An in-lir sparge system operating with inert gas in the feed system allows adjustment of powder bulk density and colour. The enlarged conical section of the drying chamber separates the dried coffee from the drying air so effectively that virtually all the powder leaves the base of the chamber, where it is cooled, screened and passed to storage, packing or agglomerationINSTANT COFFEE CLEANING AND BLENDING The first step in the processing line is a thorough cleaning of the green coffee beans, to removedefectivebeans and extraneous matter. Blending is usually carried out to achieve optimum flavour development in the roasting stage. RO&TIJXGANDGRINDING Roasting enhances the flavour and aroma and may be carried out batch-wise or continuously. The latter continuous method is more cost effective. Grinding to a particle size most suitable for the extraction process follows. EXTRACTION This is eithercontinuousorbatch. Thecontinuous method employsa tiltable jacketed pressure vessel containing two helicoidal conveyors. Hot water enters the top end and the extract flows through the trough by gravity. The dwell time is from 30 to 40 minutes. In two stage extraction, atmospheric pressure is used in the first stage and pressure in the second. Batch extraction is carried out in a counter-current column battery unit featuring split extraction under closely controlled conditions, and yields of over 48 percent can be achieved. The first stage produces a prime quality extract, which is held separately pending final pretreatment and drying. The second stage produces a high overall extract yield but with low solids and this has to be subsequently concentrated. CONCENTRATION Two methods are used, eithera two stage falling film evaporator with aroma recovery section, or a rotary thin film evaporator designed uniquely by Niro for heat sensitive products. Both types of evaporator operate undcr vacuum, thereby maintaining low extract temperatures. SPRAY DRYING The concentrated extract is pumped to the pressure nozzle in the drying chamberwhereit isatomizedand contacted with hot air. Drying temperatures are low in order to preserve aroma and flavour in the dry product. An in-line spargesystem operating with inert gas in the feed system allows adjustment of powder bulk density and colour. The enlarged conical section of the drying chamber separates the dried coffee from the drying air so effectively that virtually all the powder leaves the base of the chamber, where it is cooled, screened and passed to storage, packing or agglomeration. 198