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- Title
Fouling of polyethersulphone ultrafiltration membranes during the decaffeination of ground coffee brews.
- Authors
Manios, Triantafyllos K.; Mattia, Davide; Bird, Michael R.
- Abstract
The production of reduced caffeine coffee beverages (so called 'half-decaf) has recently gained increased commercial attention. Ultrafiltration (UF) can offer a viable alternative to the use of solvents in the decaffeination process, also operating at ambient temperatures, and a low operational cost. This paper reports the development and evaluation of the fouling occurring during the selective reduction of caffeine from coffee brews using a commercially available synthetic tight ultrafiltration (TUF) polyethersulphone (PES) membrane (GP95PP - Alfa Laval) with a 2 kDa molecular weight cut off (MWCO). Performance is reported in terms of fluxes, hydraulic resistances, and component rejection ratios. A cross-flow rig was operated at transmembrane pressures of 2-9 bar and cross-flow velocities of 0.04-0.1 m/s at temperatures in the range 25-50 oC. The process is viable: a retentate is produced with a much reduced caffeine concentration whilst still rich in higher molecular weight bioactives. Commercial PES membranes (GP95PP - Alfa Laval) had a permeate flux of 6.5 L m-2 h-1 and a fouling index (FI) of ca 60%. Rejection ratios were ca 30% for caffeine, 2 90% for both polyphenols & proteins, & 2 80% for melanoidins, over a 29 hr filtration period. Membrane surface modification due to fouling takes place, altering the hydrophobicity, An effective cleaning protocol is reported comprised of 0.5% w/v NaOH at 500 C. The flux decline and recovery are reported for multiple fouling and cleaning cycles.
- Subjects
ALFA Laval Inc.; COFFEE grounds; ULTRAFILTRATION; COFFEE brewing; FOULING; COFFEE; MOLECULAR weights
- Publication
Food & Bioproducts Processing: Transactions of the Institution of Chemical Engineers Part C, 2022, Vol 136, p14
- ISSN
0960-3085
- Publication type
Article
- DOI
10.1016/j.fbp.2022.09.005