Separation and Purification Technology, Vol.164, 163-169, 2016
Pressure cycling extraction as an alternative to percolation for production of instant coffee
Pressure cycling (300 s at 91.4 kPa + 300 s at 338.2 kPa per cycle) was performed to extract water-soluble compounds from ground coffee at approximate to 17 degrees C. The efficiency of solute removal (E) at equilibrium, and the extraction rate constant by dispersing the solids in the solvent (k) were examined. The obtained aqueous solution was freeze-dried at approximate to 2.25 Pa for 48 h and the produced instant coffee was analyzed by GC-MS to speculate about its quality. For comparison, an additional set of experiments by involving three different extraction procedures was also carried out (i: infusion at 91.4 kPa and approximate to 17 degrees C; ii: infusion at 91.4 kPa and approximate to 100 degrees C; iii: pressurized extraction at 338.2 kPa and approximate to 17 degrees C). Pressure cycling extraction presented the optimal E (79 +/- 6%), and a k (2.9 x 10(-3) s(-1), or 1033 s to reach equilibrium) comparable to that found at 100 degrees C in percolator batteries of commercial extractors. The qualities of lyophilized coffee from pressure cycling extraction and from the best expected condition of extraction for the purpose of retention of coffee volatiles (i.e.; 91.4 kPa and approximate to 17 degrees C) were analogous. (C) 2016 Elsevier B.V. All rights reserved.
Keywords:Extraction;Freeze-drying;Coffee extract;Instant coffee;Efficiency of extraction;GC-MS analysis;Coffee volatiles;Aromatic hydrocarbons