BREWING
the spent hop slurry for dosing as a bittering hop in the brewhouse. With a maximum hop load of 45kg, the Alhop is limited to medium sized breweries (or microbreweries undertak- ing extreme dry hopping). For larger breweries Alfa Laval offer the Iso-Mix External Drive (IMXD). The IMXD is a motor-driven rotary jet mixer which can be tted to the base cone of a cylindroconical vessel. The jet mixer agi- tates and mixes the contents of the vessel and is fed by a recirculation pump. As well as enabling dynamic dry hopping in a single vessel, the system is also used to homogenise the vessel contents before processing through a centrifugal separator to reduce spikes in solids level in the feed beer. With a separate mixing tank to suspend the hops maintaining a particle concentration that the unit can handle, it is also possible to dose a dry hop slurry into vessels using the IMXD. Lervig Brewery in Stavanger, Norway have several IMXDs which are used to dry hop 250hL batches with up to 200kg of hop pellets. Mike Murphy the Lervig Head Brewer reports improved extraction efciency, reduced beer losses and the ability to “push the hoppiness of the beer to a higher level” through the use of IMXD. GEA HOPSTAR Dry In the GEA HOPSTAR Dry, the hops are loaded manually into a purged mixing vessel which is then lled with beer. The pellets are disaggregated and extracted by mixing with an agitator. The hops are then left to sediment out onto a screen in the base of the vessel. Fresh (un-dryhopped) beer is then run into the base of the mixing vessel at lower velocity than the sedimentation velocity of the hop material. As ow up through the hops is so slow, the bulk of the hop solids remain on the screen in the mixing vessel. Any solids which do get entrained are removed in an inline screening section where a sieve and rotating scrapers hold back all particles above 100µm. The number of cycles of mixing and elution can be varied to achieve the desired level of extraction of hop compounds. After elution is complete the beer above the internal screen is drained under top pressure and a ush with DAW is also possible to minimise beer losses. To ensure dry hopping on large conditioning vessels is homogeneous, the system is used with jet mixers (similar to the IMXD).
Alfa Laval Alhop skid
water to CIP effectively. It also blocked fairly regularly and gave high levels of hazes which were difcult to remove. The HopGun has been attered by imitators in recent years with several companies selling equipment which looks very similar, many with ballistically- themed names. Alpha Laval Alhop In the Alhop, hops are added to a tank which is on a recirculation loop down the centre of a cylindrical screen. After purging the tank and loop, the system is lled with beer. The beer and hop pel- lets are recirculated to break down the hops and start the extraction process. Once fully homogenised, more beer is introduced into the recirculation loop while dry hopped beer is taken off through the screen. This process is continued until the desired extraction is achieved. Because the beer is owing down the screen as well as across it, the screen blocks at a slower rate. The system can then recover beer left in the recirculation loop by pushing out the beer with CO 2 and washing the spent hop with deaerated water. The Alhop also offers the opportunity to use
Braukon HopGun The Braukon HopGun works on the same basic principle as the Torpedo only the hops (usually pellets) sit on the outside of the strainer which is mounted in the centre of the cylinder. Beer enters tangentially through the side of the cylinder causing a rotation of the beer/hop material inside. A candle strainer in the centre prevents the larger hop solids leaving the unit, with the rotational movement of the beer mixing the con- tents and slowing the blocking of the strainer. A range of sizes are available to process up to 100kg of hops. Andrew Patterson (then Head Brewer) purchased a HopGun
to improve and standardise dry hopping at the Dark Star Brewery, Sussex, UK. Yields were improved signicantly, and the time taken to extract aroma was reduced from a week to a few hours. On the downside he did nd the unit was a big lump to move
and work around in the brewery and took a great deal of time, effort and
The Alfa Laval Iso-Mix External Drive (IMXD)
44 ● BREWER AND DISTILLER INTERNATIONAL I october 2019
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