Pressure cycling extraction as an alternative to percolation for production of instant coffee

• Pressure cycling extraction of water-solubles from coffee was investigated.
• Instant coffee produced by freeze-drying the extract was analyzed by GC–MS.
• The efficiency of extraction by cyclic pressurization and by infusion was the same.
• The number of extracted species by pressure cycling was higher than that by infusion.
• Pressure cycling extraction was more effective than infusion to keep coffee volatiles.

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 ≈17 °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 ≈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 ≈17 °C; ii: infusion at 91.4 kPa and ≈100 °C; iii: pressurized extraction at 338.2 kPa and ≈17 °C). Pressure cycling extraction presented the optimal E (79 ± 6%), and a k (2.9 × 10−3 s−1, or 1033 s to reach equilibrium) comparable to that found at 100 °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 ≈17 °C) were analogous.

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