Lager made with the 133-year-old yeast that forever changed beer is surprisingly tasty

For a long part of humanity’s history, beer was more than an after-work or weekend beverage. In many years and in many cultures, going back to at least the construction of the pyramids of Egypt, daily rations of beer helped fuel workers throughout their days.

More recently, factory workers used those malted rations to get through their labour.

And while the taste and alcohol content of many of these beers varied greatly, it turns out that by the end of the 19th century, at least some factory workers were downing a brew that would still be considered surprisingly tasty by today’s standards.

We know this because near the end of the 2016, Business Insider had the chance to visit Brooklyn Brewery for an event hosted with the Danish brewery Carlsberg to try a beer made with 133-year-old yeast that had been extracted from one of the first bottles of lager ever brewed with purified lager yeast.

This wasn’t just a copy of a beer dating back to those days, it actually used an ancient ingredient. That still-living yeast was taken from one of those more than 100-year-old bottles and was used to create a fresh batch of beer according to the original specifications of 19th century brewers: the Carlsberg Rebrew.

A dark lager with a rich brown colour and a taste that resembles a good bread, complex without being too heavy or malty, the Rebrew was more interesting and flavorful than many modern lagers.

“Elegant rather than dense, at 5.8% abv it’s in the style of a Munich dark lager, the style of the day, the dark colour being driven by the specially kilned malts,” Susanna Forbes writes, describing the same beer for Imbibe Magazine. “The flavours of rich toffee are accompanied by some residual sweetness.”

Carlsberg RebrewKevin Loria/Business InsiderCarlsberg’s Bjarke Bundgaard showed this copy of the 19th century brewing records that were used to create the Rebrew.

Perhaps most importantly, it’s a very drinkable brew — essential since factory workers at the end of the 1800s drank quite a lot of it.

Every worker got four litres of beer as their daily ration at the time, according to Bjarke Bundgaard, a beer historian for Carlsberg, the Danish brewery behind Rebrew.

“People drank quite a lot then,” he tells Business Insider. Though, he says those brews probably had significantly lower alcohol content.

Why the precious ingredient in Rebrew is so special

If there’s a magic ingredient in beer, it’s yeast.

It’s the tiny living organism that takes the grain, hops, and water you have beforehand and converts that mixture into the delightful beverage that human civilisation has celebrated for thousands of years.

But it was only in the 19th century, relatively recently in the history of beer, that scientists isolated yeast itself, understanding the full role that these tiny creatures played.

Different types of yeast make different beers. While some produce consistent and predictable results, others can be incredibly unpredictable.

In the latter half of the 19th century, a number of scientists — pioneers of microbiology — were starting to crack the mysteries of fermention, realising that yeast was responsible for the seemingly magical transformation of water into beer. Louis Pasteur was one of those researchers and is frequently credited with revealing many of the mysteries of fermentation, but it was in 1883 that Emil Christian Hansen, a researcher at the Carlsberg Laboratory (Carlsberg conducts scientific research alongside their beer-making operation), actually managed to isolate the yeast that was considered the key to lager production.

Lager had skyrocketed in popularity at the time. But many batches of the cold-fermenting beer would spoil, contaminated by wild yeast. In order to prevent that spoilage, researchers realised they’d have to identify the species that made the perfect lager, using that and only that for fermentation. That was the inspiration for Hansen’s work, and after the discovery, the brewery reportedly shared that special lager yeast with the rest of the industry.

There are different varieties of yeast that can be used for lager, but that original species, Saccharomyces pastorianus, was the main one that most future lagers would use. And according to scientists at Carlsberg, the genetic sequence of the specimen they took from those old bottles for the Rebrew project is essentially a perfect match for the original samples in their gene bank.

S. pastorianus is the name for that yeast that has won precedence today, a name in honour of Pasteur. But Hansen had called the yeast by another name, one that was considered a synonym for its current moniker for some time, Saccharomyces carlsbergensis.

And at Brooklyn Brewery, where Business Insider had the chance to taste the Rebrew, brewmaster Garrett Oliver claimed that some circles still go by that name.

“We still refer to lager yeast as carlbergensis,” said Oliver.

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