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New Dry Hopping Concept
„One pound weight of the best hops, as taken from the pocket, should be infused into each barrel of ale” is a recommendation from the second half of the 19th century for brewing a Pale Ale. Nowadays, extreme beer styles can also be found, sometimes with multiple hop applications of over 2 kg/hl.
Based on the findings of a research paper originally published in BrewingScience, banke GmbH, Taufkirchen, Germany, developed a large-scale industrial cold hopping system under the name LoopulEX and put it into operation in several breweries in 2021 in quantities ranging from 100 to 3500 kg of hop pellets per batch.
Process diagram of the new dry hopping system, exemplified as a two-tank process with a decanterThree-stage process
In this system, the dry hopping process can be broken down into three process steps which, as illustrated in the diagram opposite, run in chronological order:
- Dispersing and dissolving the hop pellets in beer;
- Extraction of the aromas from the hop particles and transfer of the hop aromas into the beer;
- Separation of the hop particles.
Overview of the dry hopping systemDispersing and dissolving the hop pellets
The aim of the first step is to dissolve the pellet structure and expose the hop particles for extraction so that the aromas are fully accessible to the liquid phase and can be extracted. The hop mass concentration of such a suspension can be selected to a maximum, resulting in a compact plant size. From a process-technical point of view, hop solids concentrations between 6.5 - 8.5 mas.% have proven themselves in practice here. In order to accelerate the dispersing process, an agitator is used which is gentle on the yeast but at the same time quickly breaks down the hop pellets into primary particles. This means that this first step takes only 30 - 60 min, depending on the respective hop variety and pellet properties. In this highly concentrated hop suspension, many hop aromas are oversaturated and cannot be optimally extracted.
Dispersing and dosing system unit with automatic filling for batch sizes up to 1000 kgTransfer of hop aromas
In the second step, the hop-beer suspension is added to a beer stream, thereby significantly lowering the hop mass concentration locally. This dilution and the resulting increased concentration gradient enable an ideal extraction of the hop aromas into the beer. Thus, an extraction efficiency is achieved that is similar to using the entire beer volume in the tank. This new ideal extraction balance is achieved within one minute in the holding and mixing section on the way to the decanter.
Mode of action of the redilutionSeparation of the hop particles
After the hop aromas have been extracted, the hop particles are separated by a solid-liquid separation in the final third step. Two technologies can be used for this, depending on the quantity of beer produced. For smaller quantities, a special hygienic curved sieve can be used, for larger quantities a decanting centrifuge. The systems differ in the degree of separation and the dry substance content.
With decanter technology, up to 96 percent of the beer can be recovered from the hop sludge with separation rates of 98 percent. The separated hops have a dry substance content of 32 - 38 percent. This means, for example, that up to 15 percent more sales beer can be obtained from heavily hopped beers. The costs for waste water are also significantly reduced.
Separated hop solids after extraction with a dry matter content of 35 percentPractical experience
Thanks to these three inline process steps outside the beer tank, which run in series, hop quantities of up to 1000 kg per cycle can be realised within the LoopulEX system under ideal dry hopping conditions with process times of less than 8 hours. Automatic pellet filling of the dissolving tank allows almost any amount of hops to be processed.
In 2021 and 2022, for example, several projects were realised in which the total batch sizes ranged between 100 kg and 3500 kg of hop pellets, with beer batch quantities between 500 and over 6000 hl. Beer losses, for example, were reduced from more than 400 hl per tank to less than 14 hl, which corresponds to a saving of 96 per cent of the beer previously lost.
In addition, the time for the dry hopping process was reduced in all breweries from two to four days to less than 8 h in some cases.
Due to the high extraction efficiency, the system was able to additionally reduce the hop dosage while maintaining the aroma profile. In all cases, the desired aroma profile of the beer could be completely achieved by adjusting the process conditions in such a way that no differences between the new and old production methods could be detected in the sensory analyses carried out.
In addition, it was observed that due to the rapid separation of the hop particles, the well-known hop creep effect was significantly reduced or could no longer be detected at all.
The presented inline process of hop extraction, based on a hop-beer suspension with a high solids concentration and prompt re-dilution with beer, makes it possible to have the entire dry hopping process take place at only one central location in the brewery. Analogous to the cleaning-in-place principle, it could be called dry-hopping-in-place here accordingly.
