The Blockbräu brewery in Hamburg uses self-generated nitrogen for longer taste stability

Article Brewing and Beverage Industry 06/2020

In-House Nitrogen Production

Blockbräu has won several awards for its brewing skills in recent years. The brewery with adjacent dining experience takes the finest ingredients and innovative recipes to create finely matched flavours for its various kinds of beer, thrilling thousands of visitors every week. To retain the aromas, the inn-cum-brewery in Hamburg’s premier location by the landing stages on the river Elbe uses nitrogen in the brewing process and for filling bottles and kegs. The flavour and aroma as well as the character and quality of the beer can be ensured through the environmentally friendly use of nitrogen. A nitrogen generator produces the necessary protective gas directly on site affordably and in an environmentally friendly way.

The Blockbräu is to Hamburg as, say, the Hofbräuhaus is to Munich. The brewery with the spectacular view of Hamburg harbour is also a tourist magnet and a place of refuge for locals. With room for 450 people on 3 levels and a further 400 seats on the sunny harbour terrace, the Blockbräu is a restaurant and event location in one. But it isn’t only the panorama and copper brewhouse in the guest room that draws the guests but above all the excellent beers that are brewed here. Under the direction of brew master Thomas Hundt, about 5,000 litres of pale beer, wheat beer and Senatsbock are made here each week – that’s almost 300,000 litres per year. The Senatsbock and the new-style Hefeweizen took two awards in 2019 in the Meiningers International Craft Beer Award and the European Beerstar.

Taste and quality are everything at Blockbräu. In the brewhouse, under the watchful eyes of the guests, Hamburg brewing water, hops and malt are used to create the wort, which is then placed in the fermentation vessels. In seven tanks with a volume of 4,000 litres each, this is then cooled to 12-22 degrees and left to ferment. Four of the tanks are used to brew pale beer with an off-dry note, which is attributed to the aromatic Hallertau hops. Two of the tanks are reserved for seasonal wheat beer, which delighted customers in summer 2020 with a fresh flavour and aroma of banana and citrus fruits. In winter, the menu includes the Weizenbock – an amber-coloured, naturally cloudy stout speciality. Another tank is reserved for the legendary Senatsbock, which is brewed according to traditional recipes as a co-brewing with seven other Hamburg breweries.

Oxygen, the enemy of beer

In the unitanks, which are used in the tanking process both for fermentation and storage, the wort is created from two decoctions. After three days of fermentation without pressure, the tanks are pressurised so that the natural fermentation carbonic acid can bind in the beer. After reaching the final degree of fermentation, a two-day diacetyl rest is added to avoid a high concentration of this metabolic product of yeast and bacteria and the taste errors it causes. To mature the beer, the tanks are then cooled to 1 degree Celsius and left for a period of up to 6 weeks.

After storing, all contact with oxygen should be meticulously avoided, otherwise oxidative reactions can take place that could give the finished beer a broad and bread-like taste. In order to empty the fermentation of cooling tanks, the interior is therefore filled under pressure with a gas mixture. The mixture consisting of 50% nitrogen (N₂) and 50% carbon dioxide (CO₂) is pressed into the cylinder from the top, which expels the oxygen out of the tanks while the beer flows out at the bottom. Before filling with the next batch, the tanks are first steam sterilised and then rinsed several times with nitrogen.

From the storage tanks, the beer continues its journey to the various stainless steel bar tanks. These are pre-charged with the same N₂-CO₂ gas mixture. In this way, the necessary counterpressure is built up to prevent the pressurised beer from foaming and also to avoid the negative impact of oxygen. From the four stainless steel tanks on the ground floor, each with a volume of 2,000 litres, the beer is finally pumped to the taps on all levels of the inn-cum-brewery at 4 degrees Celsius, to the delight of the guests.

Nitrogen produced on site

The gas mixtures is prepared by a gas mixer in the brewery’s plant room. Another two tanks here, each with a volume of 280 kilograms, serve as the source of the CO₂. The requisite CO₂ is supplied by tanker as required. The requisite nitrogen, on the other hand, is conveniently produced directly on site and therefore gentle on the environment. Since the opening of the Blockbräu in 2012, a nitrogen generator from Inmatec has supplied the brewery with the requisite nitrogen. In 2017, a new, larger generator was installed owing to the increased production, especially in the area of bottle filling. The PN 1250 OnTouch extracts nitrogen from the surrounding air with the aid of pressure swing adsorption technology. To this end, the air is passed into a valve block under pressure, where it is distributed in alternation to two adsorption tanks. These towers filled with a carbon molecular sieve switch in alternation between filter mode and regeneration mode. In this way, oxygen and carbon dioxide molecules from the ambient air are adsorbed in the sieve in one vessel, while the sieve in the second vessel regenerates under compressed air relief. The nitrogen obtained in this way is passed to a product tank with a volume of 150 litres. Another 500-litre buffer vessel offers additional storage space for any production peaks. Together, the vessels store at a pressure of 11 bar a usable volume of approx. 7 m³ of nitrogen.

In this way, up to 7.9 m³ of nitrogen with a particularly high N₂ purity of 99.8% can be produced every hour, which, due to the brewery’s strict hygiene rules, is above the required food-compliant level of 99.5%. The nitrogen, together with the stored carbon dioxide, is pushed through a more than 60 metre-long beer line extending over several floors to its various points of use. The 50/50 mixture ratio of the gas is ideal for this, as it provides the ideal saturation and conveying pressure for the cool beer without causing it to carbonate, even at 2 bar.

Pre-charging, rinsing, transferring – nitrogen protects against spoilage

Moreover, N₂ and CO₂ are needed in the Blockbräu for the filling of kegs and bottles. These are steamed before use and also rinsed and pre-charged with the gas mixture. The new nitrogen generator now generates a sufficient quantity of nitrogen to support the simultaneous production of beer and the filling of bottles and kegs. Even at busy times before and after weekends, when tanks are emptied, transferred, pre-charged and purged, the generator operates at no more than 80%, providing further spare capacity for a future doubling of the bottle filling area.

The Blockbräu belongs the Block Group, a provider in the area of system gastronomy, hotel trade and food production, for which freshness, quality and regionality play an important role. For example, the filled beer is delivered to various companies of the Block Group and elsewhere. A good 100 fresh kegs go to the 5-star Grand Elysée Hotel Hamburg every year, 80,000 0.3l bottles with the brand name Just Beer are dispatched to the Better Burger restaurant chain Jim Block. In addition, various events are supplied with kegs.

“Generating nitrogen right in the brewery with a nitrogen generator is the ideal solution for us. The costs per cubic metre are well below those of the delivered carbon dioxide and so the purchase price of the extremely low-maintenance generator was amortised after just 1.5 years. Moreover, the nitrogen generator provides the required quantity of N₂ for the brewing process as well as the bottle and keg filling at all times, and we still have sufficient space to increase production. Thanks to the gas mixture that we use, the beer tastes good and stays fresh for a long time. That was ultimately a big plus point during the coronavirus slump. We are very happy with the Inmatec solution,” says Thomas Hundt, brewmaster at the Blockbräu in Hamburg.

Published in print magazine "Brewing and Beverage Industry 6/2020"
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