The beer industry is potentially interested to replace conventional diatomaceous earth (DE) filters with crossflow microfiltration (CFMF) systems to get rid of the environmental and safety concerns connected with filter-aid handling and spent filter sludge disposal.
Since the year 2000, rough beer clarification may be carried out by resorting to three different membrane systems, namely those proposed by Norit Membrane Technology/Heineken Technical Service, Alfa-Laval AB/Sartorius AG, and Pall Food & Beverage/Westfalia Food Tech. Whereas the Norit/Heineken or Pall Food & Beverage CFMF units consist of polyethersulfone (PES) hollow-fiber modules with pore size of 0.50 or 0.65 ?m, respectively; the Alfa-Laval/Sartorius CFMF units are made of PES flat-sheet cassettes with pore size of 0.60 ?m. The main problem with such systems is that the average beer permeation flux through PES membrane modules is about a fifth of that (250-500 L m-2 h-1) obtained with powder filters.
By using a ceramic single-tube membrane module with nominal pore size of 0.8 ?m under constant feed superficial velocity (vS=6 m s-1), transmembrane pressure difference (TMP=3-4 bar), temperature (T =10.0±0.5 °C), and periodic CO2 back-flushing in conjunction with pre-centrifuged, polyvinylpolypyrrolidone (PVPP) stabilized, and 2.7-?m cartridge filtered rough pale lager produced in the industrial brewery Birra Peroni Srl (Rome, Italy), it was possible to reduce the permeate chill haze to (0.31±0.06) EBC unit, as well as increase the average permeation flux to a value (337±1 L m-2 h-1) quite near to that achievable with conventional DE-filters (Cimini and Moresi 2015 J Food Eng 145: 1–9).
Unfortunately, the scaling-up of such CFMF process from a ceramic single-tube membrane to a multi-channel monolithic module is hampered by the fact that the inner channels of the monolith may be poorly back-flushed by the local CO2 flow rate, thus yielding permeation fluxes quite lower than those obtainable in a ceramic single-tube membrane.
To scale up the aforementioned process, it would be more advantageous to rely on hollow-fiber (HF) membrane modules, for several reasons: i) the high packing density, ii) the relatively low-power consumption, and iii) the capacity to withstand back-flushing procedures. Unfortunately, the membrane life span of the polymeric HF membrane modules is as short as two years.
By using the novel ceramic hollow-fiber membrane module consisting of 40 tubular elements with inside and outside diameters of 3 and 4 mm, length of 200 mm, and pore size of 0.8 ?m, recently manufactured by Hyflux Ltd (Singapore; http://www.hyfluxmembranes.com/inocep-ceramic-hollow-fibre-membrane.html), it was possible not only to offset the well known ineffectiveness of back-flushing cleaning techniques in ceramic multi-channel monolithic modules, but also to obtain a superior CFMF performance with respect to that the polymeric HF membrane processes patented by Heineken and Norit Membrane Technology. Moreover, the extended membrane life span of the ceramic HF modules up to ten years would reduce the contribution of the annual membrane replacement to the overall operating costs of beer clarification. (Cimini and Moresi 2015 Food Bioprocess Technol, DOI 10.1007/s11947-015-1575-z).
Further work is directed to assess the effect of HF membrane porosity on the main characteristics of the beer permeate collected.
Alessio Cimini (firstname.lastname@example.org), Mauro Moresi (email@example.com)
Department for Innovation in the Biological, Agrofood and Forestry Systems, University of Tuscia, Via S. C. de Lellis, 01100 Viterbo, Italy