Significant shrinkage reduction thanks to tank geometry and surface properties in cylindroconical fermentation tanks

Practical findings from BrauKon long-term trial I Beer shrinkage has always been one of the biggest challenges in breweries with regard to efficient beer production and maximising the sales beer. Especially in the production of hop-emphasised craft beers, where hop plugging is often applied, the beer yield is drastically reduced. Thanks to the latest practical findings from a BrauKon long-term trial, a significant reduction in shrinkage can now be achieved by adapting two features within the cylindroconical fermentation tanks (ZKTs) – essential are a special surface finish and a defined cone angle.

The need for the long-term test by the plant manufacturer BrauKon arose in the context of a tank expansion. By adding two new fermentation tanks to two existing tanks in a customer project, it quickly became apparent that the quantities of beer bottled from the respective tanks varied greatly. A comparison of the bottling reports showed that the efficiency of the existing tanks was better than that of the new ones. This also led to the need to take a closer look at the topic of shrinkage reduction in combination with the possible influencing factors in cylindroconical fermentation tanks.

The role of the cone and the surface finish

The differences between the two different types of tanks were worked out and compared together with the parameters that seemed to be responsible for increased efficiency. It emerged that the ZKTs differed significantly in two characteristics: the cone opening angle and the surface finish of the respective tank.

While tank 1 had an opening angle of 70°, tank 2 had an opening angle of 60°. Furthermore, the tanks differed in their surface condition of the inside of the cone. The surface in tank 1 had a longitudinal grind with electropolish, tank 2 only the “classic” longitudinal grind. These two different characteristics led to the decision to carry out the long-term test with four different tanks and with the standardisation of all other variables in the beer production process. In the end, it was hypothesised that these two factors mentioned above could be the cause of the different efficiency. The aim of the practical trial was thus to compare the beer loss that occurs during the production of hop-stopped beers in the different cylindroconical tanks (ZKTs).

Each tank was filled between seven and eleven times on average over a period of twelve months. Four tanks of 60 hl each were used:

Tank 1 with 60° cone opening angle and classical longitudinal grinding

Tank 2 with 60° cone opening angle with classic longitudinal grinding and electropolishing <0.3 µ roughness

Tank 3 with 70° cone opening angle with classic longitudinal grinding

Tank 4 with 70° cone opening angle with classic longitudinal grinding and electropolishing <0.3 µ roughness

Traditionally high Schwand, especially for hop-accentuated craft beers.

In the production of strongly hoppy and fruity aromatic beer styles, such as Pale Ales and India Pale Ales, the technique of hop tamping is widespread and is used to flavour the beers in a natural way. This is done almost exclusively with hop pellets, which have the positive property that they dissolve as soon as they come into contact with beer and release the bound essential oils directly into the beer. The major disadvantage of hop plugging, however, is a very high beer loss, as hop pellets absorb up to 6 times their own volume of beer when used, without releasing it again in the further production process. Hop plugging, also called “dry hopping”, can thus increase shrinkage by up to 50 per cent, depending on the amount of hops and hop products used.

In the daily handling of this technology in combination with the use of a wide variety of hop varieties, hop quantities and hop products, it is well known that shrinkage can vary. Until the latest BrauKon field test, however, no attempts had yet been made to take a closer look at the responsible parameters of tank geometry and composition and to work out which production factors or materials can be adjusted to limit shrinkage and thus increase beer yield. Through BrauKon’s long-term trial at Mrs Gruber in Gundelfingen (formerly Camba Old Factory), an industry-wide solution has now been found that goes hand in hand with a significant increase in the efficiency of the fermentation tanks and a maximisation of yield. However, when it comes to increasing efficiency in beer production, it is not uncommon to assume that maximising yield is accompanied by a reduction in the quality of the beer. The current long-term experiment now proves the opposite.

The beers used were exclusively hop-stopped India Pale Ales, Imperial India Pale Ales and Triple India Pale Ales. The aim was to determine the beer loss and a possibly higher yield with over 40 tank occupancies in just over a year and under constant practical conditions, and to show the potential for savings. Subsequently, the practical test from Gundelfingen was confirmed on Camba Bavaria’s own brewing plant at BrauKon’s headquarters in Seeon. The result: Overall, up to five per cent difference in the yield of hop-stopped beers could be achieved.

Standardisation of other influencing factors

With regard to the comparability and significance of the results obtained, it was essential to create the same basic conditions for each tank and for the other influencing factors that play a significant role in beer production. In the long-term practical trial, all other variables, such as the yeast strain and quantity, the hop product and quantity, and the hop plugging technique, were therefore standardised. In addition, a constant tank volume was used.

Auswahl des Hefestamms und Menge

Hefestämme besitzen unterschiedlichste Eigenschaften, die sowohl direkten Einfluss auf das Gärverhalten als auch auf das Bier selbst haben. Die Vermehrung der Hefe und die Bildung von Biomasse sowie deren Sedimentationsverhalten ist von essentieller Bedeutung, da sie maßgeblich an den Schwänden und Bierverlusten beteiligt sind. Aufgrund dieser Eigenschaft der Hefe wurden daher der Hefestamm und Hefemenge (Hefezellen / ml) im Langzeitversuch standardisiert. Der Vergärungsgrad der gewählten Hefe lag im Schnitt zwischen 75 – 82% und besitzt ein schwaches- bis mittelmäßiges Sedimentationsverhalten – was bei dieser Art von hopfengestopften Bieren – den „Hazy IPAs“ – absolut erwünscht ist. Die Menge der Zellzahl bei der Hefegabe wurde ebenfalls standardisiert.

Auswahl der Hopfenprodukte und Menge

Noch wichtiger bei der Standardisierung der Parameter war die Auswahl der Hopfenprodukte sowie der Menge, die beim „Dry Hopping“ der Biere Verwendung finden. Einige Hopfenprodukte unterscheiden sich eklatant in ihrem Aufbau bzw. ihrer Zusammensetzung und somit auch in ihrer Wirkungsweise und ihrem Sedimentationsverhalten. Letzteres ist maßbeglich dafür verantwortlich, wie hoch die Bierschwände ausfallen. Bei Hopfenpelltes, die aus größeren Pflanzenbestandteilen bestehen, (wie Typ 90) sedimentieren deren Bestandteile erfahrungsgemäß deutlich schneller, als bei Hopfenpellets, die aus kleineren Pflanzenbestanteilen (wie Typ 45) bestehen. Aufgrund von Schwerkraft setzen sich die großen Pflanzenbestanteile schneller ab. Dies hat zur Folge, dass die Trennung zwischen Feststoffen und Bier zum einen schneller stattfindet und sich zum anderen die Lagerzeiten der Biere verkürzt. Ein weiterer großer Vorteil zeigt sich auch darin, dass der „Kalttrub“, bestehend aus Eiweiß, Hefe und überwiegend Hopfen, deutlich kompakter ist und sich dieser schneller und einfacher vom Bier trennen bzw. entfernen lässt. Aufgrund dieser Eigenschaften wurden für den Praxis-Versuch überwiegend BBC Pellets und Typ 90 Pellets im Mengenbereich zwischen 10-15g/l verwendet.

Standardisierung des Abschießens

In order not to unnecessarily increase the shrinkage and beer loss in the field test, the process of draining was limited to two employees and the amount drained was determined. It was also determined to drain only the sediment that settles at the 1.5°C cooling and as little liquid as possible.

Maximum shrinkage reduction: A BrauKon ZKT with 70° cone opening angle in combination with an electropolished surface.

From the direct comparison of the shrinkage results of the tanks (Table 1-4) it was clearly evident that the type of surface finish has a definite influence on the efficiency of the tanks. The electropolishing technique for both the 60° cone opening angle and the 70° cone opening angle showed a significant reduction in shrinkage. The electropolished tank achieved up to 3.5% more yield compared to the classic longitudinally ground tank. Furthermore, the hypothesis regarding the influence of the cone opening angle on the shrinkage was clearly proven. Contrary to expectations, the use of the flatter cone opening angle of 70° proved to be a clear advantage over the classic 60° cone opening angle – here between 2.6 -3.8% shrinkage reduction could be achieved in the long-term tests.

The following classification underlines which tank with which features works best and thus demonstrates the lowest shrinkage and highest efficiency:

• Platz 1. ZKT mit 70° und Elektropolitur 22,48%
• Platz 2. ZKT mit 60° und Elektropolitur 25,01%
• Platz 3. ZKT mit 70° und Längsschliff 26,01%
• Platz 4. ZKT mit 60° und Längsschliff 29,89%

Der flachere 70°-Konus-Öffnungswinkel in Kombination mit einem polierten Konus-Inneren wies mit 22,48% mit Abstand den geringsten Schwand auf.

Table 1: Evaluation ZKT 70° with longitudinal grinding

Tankbelegung	Kaltwürze in hl	Abfüllmenge in hl	Schwand in hl	Schwand in %
	42,4	30,8	11,4	27,01
	38,9	28,7	10,2	26,22
	42,2	32,3	9,9	23,42
	40,7	30,9	9,8	24,0
	41,6	29,9	11,7	28,06
	41,7	30,7	11,0	26,38
	41,9	30,1	11,8	28,13
	41,7	30,5	11,2	26,89
	40,9	31,1	9,8	24,00
	Durchschnittlicher Schwand:	26,01%

Table 2: Evaluation ZKT 70° with electropolish

Tankbelegung	Kaltwürze in hl	Abfüllmenge in hl	Schwand in hl	Schwand in %
	43,0	32,3	10,7	24,81
	42,3	33,0	9,3	21,99
	40,2	31,5	8,7	21,64
	42,0	32,9	9,1	21,63
	62,7	48,7	14,0	22,3
	40,3	31,9	8,4	20,92
	41,1	31,2	9,9	24,09
	Durchschnittlicher Schwand:	22,48%

Table 3: Evaluation ZKT 60° with longitudinal grinding

Tankbelegung	Kaltwürze in hl	Abfüllmenge in hl	Schwand in hl	Schwand in %
	64,0	48,4	15,6	24,38
	42,2	30,3	11,9	28,17
	42,0	26,0	16,1	38,21
	43,1	29,8	13,3	30,83
	36,2	25,3	10,9	30,09
	39,6	29,0	10,6	26,8
	41,0	28,4	12,6	30,73
	Durchschnittlicher Schwand:	29,89%

Table 4: Evaluation ZKT 60° with electropolish

Tankbelegung	Kaltwürze in hl	Abfüllmenge in hl	Schwand in hl	Schwand in %
	41,8	30,0	11,8	28,23
	38,7	29,9	8,8	22,74
	61,8	44,7	17,1	27,67
	40,5	31,1	9,4	23,28
	40,4	31,9	8,5	21,08
	42,0	32,9	9,1	21,63
	41,8	33,0	8,8	21,05
	42,2	30,2	12,0	28,50
	42,4	31,2	11,2	26,48
	41,5	30,1	11,4	27,4
	42,1	30,7	11,4	27,01
	Durchschnittlicher Schwand:	25,01%

Conclusion I Minimising shrinkage and maximising yield are omnipresent in everyday brewing and not only provide information about the effectiveness of beer brewing, but in the best case result in a significant maximisation of the sales beer. The long-term test of the plant manufacturer BrauKon has now proven in practice that a significant reduction in shrinkage is possible by using a cylindroconical tank (ZKT) with a 70° cone opening angle in combination with an electropolished tank surface with <0.3 µ roughness, thus significantly increasing the efficiency of the tanks. This is now possible without having to sacrifice quality in the production of high-quality beers and without having to make further investments in terms of personnel, time or energy after the acquisition of the fermentation tank type. It turned out that the biomass of the cold lees collected better in the tank cone due to the flatter cone opening angle and could be removed more easily without losing too much valuable product. The test was carried out on a total of four ZKTs with different cone opening angles and tank surface conditions in order to determine the highest possible shrinkage savings. In total, even up to five percent difference in the yield of hop-stopped beers could be achieved in some cases.

Authors:

Christian Kull, Leiter Qualitätssicherung Technologie,
Entwicklung und Gesellschafter, Braukon GmbH

Enzo Frauenschuh, Geschäftsführer und Braumeister, FrauGruber Craft Brewing GmbH

Themen-Schlagwörter: BrauKon, Schwandreduzierung, Tankgeometrie, Oberflächenbeschaffenheit, zylindrokonische Gärtanks, Craft-Biere, Praxisversuche