Coffee bulk density

Spray Drying and Agglomeration. Most instant coffee products are spray-dried. Stainless steel towers with a concurrent flow of hot ak and atomized extract droplets are utilized for this purpose. Atomization, through pressure nozzles, is controUed based on selection of the nozzles, properties of the extract, pressures used, bulk density, and capacity requkements. Low inlet ak temperatures (200—280°C) are preferred for best flavor quaHty. The spray towers must be provided with adequate dust coUection systems such as cyclones or bag filters. The dried particles are coUected from the conical bottom of the spray drier through a rotary valve and conveyed to bulk storage bins or packaging lines. Processors may screen the dry product to... 

Fig. 4.6. Distribution of grain size as a function of bulk density of freeze dried coffee extract, which has been gassed with different pressures of C02 before freezing.

Yan et al. (2001), studied how bulk density of instant nonfat milk, spray-dried coffee, and freeze-dried coffee was affected by HHP processing times, particle size, and water activity. The experimental curves for each powder in Figure 10 show that the powder bulk density increased as the pressure increased but remained constant after the pressure reached a critical value of 207 MPa for spray-dried coffee and 276 MPa for freeze-dried coffee at different water activities. The final compressed densities were not significantly different. When the pressure is higher than the critical value, there are no void spaces between the agglomerates or primary particles even the primary particles are crushed, leaving no open or closed pores within. Bear in mind, it is assumed that the compression mechanisms are the same as those in the confined uniaxial compression tests. 

Most food-processing companies use spray dryers to produce powdered products. Spray drying has the ability to handle heat-sensitive foods with maximum retention of their nutritive content. The flexibility of spray-dryer design enables powders to be produced in the various forms required by consumer and industry. This includes agglomerated and nonagglomerated powders having precise particles size distribution, residual moisture content, and bulk density. As examples, spray drying of milk, tomato juice, tea extracts, and coffee is discussed. 

The major applications of dense gases, fluids above or in the vicinity of the critical point, have been for the extraction of specific compounds from solid matrices or liquid mixtures. Well-known examples include the decaffeination of coffee, extraction of olfactory compounds for the perfume and food industries, the extraction of essential oils, and the use of SCFs for the extraction of heavy fractions from distillates. These processes benefit from the selectivity of dense gases. A variety of new applications has been identified for which the properties of dense gases, other than the solvent power, are utilized. One field is the utilization of dense gases as a reactant for reactions. The dense gas processes for the production of low density polyethylene (LDPE) by free radical polymerization, and more recently, the manufacture of fiuoropolymers have annual outputs measured in bulk tonnages. 

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