Brew your own ancient beer: Yeast from 3,000

Homebrewers will soon be able to time travel with their taste buds and brew beer similar to what the Philistines in Goliath's hometown of Gath drank.

An interdisciplinary team of researchers, archaeologists and brewmasters in Israel first isolated 5,000-year-old yeast in 2019, as published in the peer-reviewed mBio journal in 2019. But now, the fruits of that discovery are about to become available for hobby brewers and sourdough aficionados everywhere, when the first batch of commercially available ancient yeast ships in December. Pre-orders are open now.

"We want to create an opportunity for every person to connect with this story, with the past, that we as a civilization have carried on for tens of thousands of years since we started fermenting," said brewmaster Itai Gutman, who previously owned a brewery in Jerusalem and now is the CEO of Primer's Yeast, the company that is selling the ancient yeast.

The idea first came up during a "night with probably too much alcohol" when Gutman started spitballing ideas with Prof. Ronen Hazan, a microbiologist at the Hebrew University's Institute of Dental Sciences and School of Dental Medicine. They started talking about whether it's possible that yeast clinging to the inside of a vessel used for beer thousands of years ago might still be evident there today, and whether it would be possible to use them to brew beer.

Hazan got in touch with a few archaeologist acquaintances, who were even more excited about the idea. They quickly sent over a number of ancient vessels for testing, both ones that they believed were used to hold beer and wine, and others to serve as a control. Hazan teamed up with his biologist colleague Prof. Michael Klutstein, and eventually, the scope of the project grew to include archaeologists and other scholars from the Hebrew University, the Israel Antiquities Authority, Tel Aviv University and Bar-Ilan University.

"I think that many people would like to know what is the taste of the beer that Goliath or King David drank, and many people would be curious to drink the wine of Jesus Christ in the Last Supper," said Hazan. "With history, we can always imagine or see something with our eyes. But this is another sense we can activate to touch the past, which is really rare."

The Primer's Yeast company spun off from academic research about a year and a half ago, with the help of Yissum, Hebrew University's initiative to usher research into commercialization.

Yeast usually eats sugar, but can also survive on its own for thousands of years because it goes through an autolysis process, "which in microorganism terms is cannibalism," explained Gutman. "The colony sacrifices old cells in order to feed new cells, and they have a stasis situation where they are not losing nor gaining material."

That's why Hazan is quick to point out that the yeast itself isn't 3,000 years old – it's the descendant of 3,000-year-old yeast. Still, it's the closest modern-day humans can come to tasting something that was used thousands of years ago, even if the rest of the beer-making ingredients are modern.

Using organic residue analysis, scientists were able to identify organic molecules that had survived in the matrix of the ceramics over the years, including the yeast microorganism. For a few vessels, the scientists sequenced the full microbiome inside of the vessel, discovering ancient bacteria and viruses in addition to the yeast microorganism, Hazan said. He said a PCR yeast test, similar to the PCR corona test, can also quickly and cheaply determine the presence of yeast inside a vessel.

"I always dreamed of being an archaeologist, and here I got a chance to combine archaeology and microbiology," said Hazan, whose day job focuses on phage therapy, or utilizing viruses to target antibiotic-resistant bacteria. "Finally, archaeology is coming to be a real hardcore science."

The scientists were able to isolate six strains of the intoxicating single-celled fungus from 21 pieces of pottery from the biblical Tell es-Safi/Gath site west of Jerusalem (ca. 900 BCE), Jerusalem's Ramat Rachel (ca. 8th to 4th century BCE), and the Bronze Age En-Besor site in the western Negev and an Egyptian brewery found on Tel Aviv's Ha-Masger Street (both ca. 3100 BCE).

Finally, archaeology is coming to be a real hardcore science

The isolated yeasts were separately brewed by Gutman, using the same standard modern recipe. The resulting brews had vastly differing tastes: During fermentation, the different yeasts emit different gasses with flavors or aromas based upon their genetic makeup and original source.

Those who can't wait to try the brew – or don't feel like fermenting at home – can purchase the first commercial run of beer made in cooperation with Shikma Brewery, Primer's Yeast and the Israel Museum, in honor of an exhibition that opened this month.

"The Feast" exhibition, which runs from May 12 to December 31, explores banquets, feasts and food in the Ancient Near East in the 4th-1st millennium BCE. The beer, called "Mishteh," or "Feast," is available for purchase in the museum's gift shop and at select beer stores across Israel.

Shikma created a 5% ABV copper-colored beer using its house blend of mild home-grown lightly caramelized malts and hops that allow the taste of the yeast to shine, explained Anat Meir, brewmaster of the Shikma brewery.

"As a brewmaster, the raw materials are our playground," Meir said in a video produced in honor of the beer's launch.

This beer is not exactly what people drank in ancient times. The Egyptians and Philistines would have likely flavored theirs with cinnamon, cardamom and herbs, rather than the hops used in modern ales and lagers, according to archaeologist Dr. Yitzhak Paz from the Israel Antiquities Authority, who was part of the project. For an added boost of sugar for the yeast to feed on, ancient brewers would have also likely added dates and pomegranates, he said.

Beer was a basic commodity in the ancient world and was consumed by rich, poor, adults and children, as well as used in religious ritual, according to Paz. Ancient beer was not the clear amber substance we recognize today, but would have been filled with sediment, and produced from a variety of grains, including millet, corn, sorghum and wheat. The vessels that provided the yeast organisms had filtered spouts, like a watering can, to keep the sediment out of the drinker's glass.

The single-cell organism yeast comes in over 1,500 strains and occurs naturally in a variety of habitats, including in salty seas, in soil and between sweaty toes. Many wines utilize the yeast found on grape skins, but others intentionally add different strains to produce different flavors or effects.

Until relatively recently in human history, when commercial production began around the turn of the 20th century, the strains were isolated by trial and error. Those yeast strains that were found suitable for brewing or baking were often carefully guarded in "starters," usually a soupy mix of active yeasts. Today, sourdough bread is still baked using this principle.

A Times of Israel reporter who tried one of the first iterations of beer brewed with the ancient yeast in 2019 said at the time it was "slightly sweet, with a subtle tang… and tasted [of] banana and other fruits."

The yeast that will be commercially available by the end of the year is the "PTS-900BCE" strain or the Philistine yeast from Tel Safi that dates to 900 BCE, Gutman said. This strain is very similar to baker's yeast commonly used today and one of the most common types of yeast used throughout history. Gutman said they chose this strain because it was the easiest and most versatile to produce.

Right now, they’re also working on two yeast strains related to wine, including one related to ancient Roman wine and one that was used for mead, or fermented honey wine.

In the future, the team hopes to expand beyond yeast to isolate microorganisms on ancient pottery that used to hold fermented milk products like cheese and yogurt, Hazan said.

Gutman said early on they decided to commercialize the yeast rather than brew their own beer for sale to let people take a hands-on approach to connecting with the history.

It was this magical moment where you’re not sure reality is real anymore

"Everyone has different interests in the fermentation process, and we want to give as many options to the public to connect to this unique experience," said Gutman.

Hobbyists can use the Primer's Yeast for anything from baking to fermenting. He still remembers the first time he saw the ancient yeast in action when he put it into a few small jugs to make the first batch and see what would happen.

"I saw this ring of foam coming up the top of jug, which means the fermentation process started and CO2 is being produced," said Gutman. "It was just this moment of, wow. This yeast was underground on a clay vessel for who knows how many millennia, and now it's stretching its muscles and starting to work."

"It was this magical moment where you’re not sure reality is real anymore," Gutman added. "I studied biology for many years, and I never imagined you could actually make use of a sleeping colony lost underground for so many years that's been selected by humans two or three millennia ago. That's really mind-blowing."

Gutman continued, "There's this understanding that you’re touching something that was domesticated by our ancestors, but we found it, and we can actually use it now the way they used it back then. That is just fascinating."

Amanda Borschel-Dan contributed to this report.

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