Beer is really just a by-product

Thursday 18 May 17


Preben Bøje Hansen
Food technologist
National Food Institute
+45 45 25 75 17

DTU Brewery

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At DTU Brewery, the students draw on several study programmes to learn about food equipment, hygiene, and processes. We went along to watch Rasmus carry out his first brewing session.

It is almost nine a.m. and the kettles are picking up steam at DTU Brewery. Biotechnology student Rasmus Frøding is busy at work on the grain hammer mill. It looks like grain, but the right term is malt—i.e. germinated barley. Sack after sack is emptied into the machine, as it is easier to extract taste, sugar, and proteins out of crushed grain—which is the whole aim in beer brewing.

Adding carefully weighed amounts of citric acid lowers the pH value in the 330 litres of water, which—once it has reached 58°C—will receive 90 kg of crushed malt. The grain enzymes go into shock if the pH value is too high—it should preferably be 5.3, Rasmus explains.

Rasmus carefully notes down volumes and batch numbers in the control log for the purposes of the food inspectors, who have awarded the DTU Brewery an elite smiley.

The crushed malt is added to the water in the masher. It looks like a large washing machine, where you can see inside the special filters—a DTU invention—shaped as short, round tubes on a rotating disc. Rasmus is busy now.

Photo: Marianne Vang Ryde   



Armed with a timer and a giant whisk, he controls the mashing process, where the malt is pumped up and down at three-minute intervals and the bottom filters turn each time liquid is syphoned off the top. Even though there is plenty of stirring going on, Rasmus still has to climb a ladder and use the whisk to break up any lumps.

After a 15-minute malt massage, the temperature is increased to 63°C using steam in order to release the starch—after which pumping and syphoning are repeated at three-minute intervals. Finally, the temperature is boosted all the way to 75°C to kill off the enzymes, and then the grain is drained of all that is needed to make beer.

"Beer is fun, but for me it’s more the process I find exciting."
Rasmus Frøding, MSc student

Brewing at boiling point
During the last temperature increase, Rasmus and Food Technologist Preben Bøje Hansen have fitted a hose connecting the masher to the cooking kettle. The mashed fluid is pumped across, the residual sugar flushed out of the mash using more water—and the remaining 500 litres, which have now changed name to herb—are ready to be topped up with a bag of hop balls and boiled for one hour.

A small sample of the initial herb is tapped to assess the sugar content. Everyone tastes and has a guess—Preben hits the mark with 16 per cent. Jes Hedensted, a BEng student on his second semester, has just arrived and has a taste. Aiming to become a brewer, he comes as often as he can and helps out in order to learn the craft. Now, he takes on the strenuous task of shovelling out the mash. The 90 kg malt has been transformed into 120 kg of grain mass—spent grain—as it is known in technical jargon. However, it is far from useless in Preben’s opinion, so it needs a turn in the filter press.

Photo: Marianne Vang Ryde

Rasmus takes samples at all stages of the process. He is gathering material for his master's thesis in biotechnology engineering, where he is investigating how to separate the individual substances in the excess grain.

“Beer is fun, but for me it’s more the process I find exciting,” he says.

While the herb reaches boiling point and a heavy beer aroma begins to fill the high-ceilinged room, the filter press is pasteurized with hot water. Preben fits a large spiral coupling and a funnel to the filter press, rinses again, then—a bucket at a time—begins adding water to the grain mass so the large cylindrical filters can squeeze out additional fluid when the filters roll against each other.

The activity level and the noise from the pumps reaches new heights, water flushes across the floor, Preben feeds the machine, Rasmus and Jes stand on either side and extract the grain from the press while the pressed, creamy liquid is collected in two buckets.

Rasmus takes his samples, and Jes says that he is going home to bake bread with some of the whole grain dry matter, and that he will try making oatmeal porridge with the liquid, which is high in fibre and protein.

“It tastes pretty good—almost like yoghurt drink,” he adds.

The rest in food
The filter press, which was invented by Preben and his colleague Peter Stubbe, is currently being developed and commercialized through their company Dacofi. At the same time, Preben is experimenting with bread, sausages, meat balls, and milk products containing the nutrient-rich, but low-sugar brewery by-product.

The herb has finally finished boiling. Using vacuum suction, it is transferred to the fermenter, where it is mixed with a yeast that has been used before. The yeast, which Preben has cultivated himself, can be used for as many as seven brews of beer.

Over the next ten days, the yeast will gradually consume the sugar, converting it into alcohol and CO2. As soon as the yeast stops bubbling, Preben taps the finished beer into kegs that are carbonated the day before the beer is due to be served.

What the expert thinks of DTU’s own beer


By Kaj Framke,

   Photo: Kaj Framke

I’ve been given the honour of reviewing a couple of fine beers from DTU Brewery. I normally manage the Danish beer blog—Kaj Ølblog—where to date I have reviewed almost 900 beers since 2010.

I have an academic background as opposed to technical/engineering one. I have but a humanistic approach, so my review bias will be more towards the good story rather than the technical details.

I was offered no fewer than six beers. I have chosen three to review here. I will give all six a full review on my blog at a later date.

Photo: Kaj Framke  

The pilsner—a beer everyone knows


 “A narrowly defined, but carefully selected profile that lands right in the middle.”

There is nothing quite like starting with a pilsner. The classic, most widespread standard beer type that everyone knows and which is therefore challenging to brew: the end result must be recognizable as a pilsner, while being able to stand out in a genre characterized by uniformity.

DTU Brewery’s pilsner is light and fresh with an alcohol volume of 5.5 per cent corresponding to a full-strength beer. An elegant brew with a delicious, firm meringue head—a by-product of the high protein content—brewer Preben revealed. And it makes good sense. As far as I am aware, the protein content in egg whites is also up there (but you tell me—you’re the engineers).

After a fresh and bitter bouquet of especially lime, the brew takes on a very elegant light texture. The flavour is nonetheless full with a narrowly defined, but carefully selected profile that lands right in the middle.

An initial creamy mouthfeel gradually gives way to an increasingly pleasing taste of fresh birch that lingers at the back of the throat. A strong beer of great elegance—not destined for freshers’ trip benders—which is meant as a compliment.

4½ beer glasses (out of 6)


Photo: Kaj Framke  

Recess—a recurring experiment


“An unconventional and quite unique experience”

One of brewer Preben’s annual experiments is ‘Recess’. Brewing assistant Jes gave a gripping account of how students on the course ‘Introduction to Food’ brew a beer, which they are then tested on. The leftovers from the brewing experiments are gathered together in a joint pool. Pilsner malt from Fuglsang is then added, and out of this mixture comes Recess, which therefore changes from year to year. But despair not—Preben always saves the recipe.

The brew has a lightly spiced scent with a hint of Gammel Dansk liqueur. It’s a shame that I can’t remember which spices go into making Gammel Dansk (and even sadder that I can’t be bothered Googling it).

The brew blend and the southern Jutland malt provide a slightly vinous aroma finish featuring the spicy flavour of oak. Here, carbonation (the last phase of beer brewing process, ed.) provides a generous pleasant tingle and the spicy slightly acidic nature of the oak tree aroma is particularly noticeable on tonsils and gums. An untraditional and quite unique beer experience that you would hardly expect from a random mix of student brewing experiments.

4 beer glasses (out of 6)




Photo: Kaj Framke  

 Provost Half ’n’ Half—the most popular


“Watch out! The 8.5 per cent packs a real punch!”

‘The Provost’ is reportedly extremely popular on campus. “Where’s the provost?” is apparently a common refrain at parties where the organizers have committed the faux pas of not having this brew on the wine list.

This, too, in principle at least—is a pilsner. However, it is double fermented, as we know it from the Belgian Dubbel: First, the beer brewed is brewed using standard malt and then using pure barley, where the enzymes from the ordinary malt brewing process are used to break down the starch in the barley. (That’s for you academics out there… Personally, I don’t understand a word of it—I’m simply repeating what the brewer told me).

A somewhat unpretentious, slightly acidic smell of grass suggests a light-footed, immediately accessible taste experience. But watch out! The 8.5 per cent packs a real punch! The brew stabs the tongue, palate and gums with its hot brandy scalpels, holding out the short-term prospect of joyful inebriation—followed by a thundering hangover.

A surprising accompanying sweetness gives the impression of liqueur and apple aperitif, which I drank in my time as a punk rocker. It was better than it sounds. A well-rounded experience that deserves five beer glasses.

5 beer glasses (out of 6)