BREWING
This means that oxygen control around the dealcoholisation plant and throughout the brewing process must be as tight as possible so as to not damage avour and avour stability. Given that analytically thermally dealcoholised beer has signi cantly reduced levels of volatile aroma com- pounds and thermal load is placed on the beer during the process, it unsur- prising that the avour of the beer is sometimes reported as thin, lacking in fresh, fruity aromas and carrying more bready, caramel aromas than standard beers. In addition to this, thermally dealcoholised beers can suffer from an increase of off- avours. Membrane dealcoholisation A number of different membrane-based approaches for beer dealcoholisation have been proposed and operated exper- imentally. Dialysis and osmotic distillation have both been trialled commercially but only reverse osmosis and nano ltration have made it to the wider marketplace. For the purposes of this article reverse osmosis (RO) and nano ltration (NF) are effectively the same process. The only difference between the two is the pore size of the membrane and some pore sizes t both classi cations. Osmosis is the process whereby a solvent moves from an area of low-sol- ute concentration to an area of higher solute concentration across a semiper- meable membrane in order to achieve an equilibrium. The osmotic pressure is that which is required to hold the sol- vent back on the more solute concen- trated side of the membrane. Reverse osmosis reverses the process by applying a pressure greater
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Ethyl acetate Isoamyl acetate Isoamyl alcohol
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Feed beer
DeAlcoTec
Alternative
Volatiles in dealcoholised beer from CENTEC unit vs competition
into the dealcoholised beer stream once this is cooled. As some ethanol is also collected during this recovery, the beer produced from the blending cannot be below 0.05% ethanol unless made so by dilution. To adopt a thermal system, you have to be pretty serious about pro- ducing AFBs. Thermal plants are big beasts and require either a very high ceiling or one with a great big hole in it. The maintenance costs for mechanical systems are very high with a full strip down required annually. In addition you have the fact that you are making a highly ammable and in the right conditions, explosive liquid. Part of the plant will be subject to ATEX zoning considerations. Despite the use of the vacuum to enhance evaporation
column which is packed with ne sheet stainless-steel to increase the mass transfer surface. Vapours formed from the dealcoholised beer are fed into the bottom of the column. They rise upwards inside the column in counter current to the falling warm liquid beer absorbing the volatile ethanol from the product. The less volatile com- ponents fall to the column base and ow into the falling lm evaporator that generates the vapour for the dealcohol- isation of the warmed beer entering the column at the top. A vacuum ow through unit is maintained and controlled by a vacuum pump. Operating at a greater degree of vacuum than analogous technologies, the maximum temperature of operation is below 40 ° C. The volatiles from the original product can be separated in an aroma recovery system and added back to the nished product. With this system the option of a recti er is available allowing concentration of the ethanol up to 90% ABV. CENTEC claims its system is the gentlest available technology – work undertaken at Weihenstephan Univer- sity is used to support this. A unit has recently been installed in Gaffel Brauerei in Cologne, Germany who is reported to be very pleased with the alcohol-free version of its Kolsch. Alfa Laval makes an equivalent technology (the imaginatively named dealcoholisation module) which uses culinary steam as the ethanol stripping agent in a column based on those used in its ALDOX deaerated water produc- tion systems. In the Alfa Laval unit the volatiles are recovered by cooling after the degas- sing stage and can be blended back
thermal systems do increase the thermal load on the beer.
GEA AromaPlus (Courtesy of GEA)
BREWER AND DISTILLER INTERNATIONAL ● 4
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