The yeast lives: Aharon Maier of TAU holding a Philistine beer vessel from Gath Yaniv Berman, courtesy of the IAA
Lechaim!

Israeli Archaeologists Resurrect 5,000-year-old Yeast and Make Beer From It

Scientists found microbes that survived for thousands of years inside pores in the clay of ancient pottery used to make and store beer and wine



If you want to walk like a drunk Egyptian, look no further than a new study by Israeli researchers who have detected yeasts used to make beer as much as 5,000 years ago - and whose microscopic descendants still survive in the clay of the vessels used to produce or store the drink.

The yeast may have spent at least some of that time in spore form, says Ronen Hazan, a microbiologist from the Institute of Dental Sciences at the Hebrew University of Jerusalem. Or, when circumstances were inauspicious, the cells may have simply gone into low-metabolism mode, breathing, eating and procreating extremely sluggishly. Either way, the colonies of yeast survived thousands of years to make it to this day.

Think of bears hibernating in winter. They slumber while not eating for months, and survive the fast because their systems enter a state of extremely low metabolism. Ditto the yeast, albeit because of being trapped in a buried clay pot, not snowed in.

More importantly, these hardy single-celled microorganisms are still capable of producing the alcoholic beverages they once fermented for kings, pharaohs and the simple folk of the Levant, in some cases more than 5,000 years ago. The team of archaeologists and microbiologists brewed various kinds of “aromatic and flavorful beer” using yeast strains that were extracted from ceramics found at different archeological sites across Israel, they report.

The best brews were “taken for additional compound and flavor analyses,” and the results were published last month in mBio, a journal of the American Society for Microbiology. Whether such “additional analyses” involved a group of scientists hanging around a lab and chanting “Chug! Chug! Chug!” while quaffing beer fit for a pharaoh is something that Haaretz has been unable to confirm.

Anyway, the point of the study was not just to get researchers classically buzzed. It was to serve as a proof-of-concept for a new method that could help archaeologists better understand the diets, habits and daily lives of ancient peoples, says Hazan. The concept is that microbial colonies isolated from the environment can survive, whether by sporulating or by metabolizing at glacial rates, for thousands of years, and the microscopic descendants of the original microbes could shed light on how people lived back then.

The postulation was that yeasts used to ferment liquids in ceramic storage jars, jugs and other pottery vessels would have colonized the pores of the ancient containers, Hazan explains.

While civilizations rose and fell around them, the yeast colonies survived for millennia in their ceramic homes. They were buried underground but would occasionally perk up under appropriate circumstances, for instance when it rained, says Hazan, who did the work with his colleague Dr. Michael Klutstein, with archaeologists Prof. Aren Maier (at Gath) and Yuval Gadot (at Ramat Rahel), and with the beer maker Itai Gutman.

Using light microscopy and genome sequencing, the researchers were able to locate and identify the descendants of the original population of yeasts hidden in the ceramic pores, he says.

The researchers sampled pottery from different locations and periods, selecting vessels which could be linked to alcohol production or consumption, either because of their shape or the context in which they were found.

The oldest vessels came from Ein Besor, an Egyptian site in the northern Negev desert, and from the remains of an Egyptian brewery uncovered during construction work in Tel Aviv. Both sites have been dated to the end of the 4th millennium B.C.E. – more than 5,000 years ago.

The archeologists also sampled jugs found in the Philistine city of Gath, today known as Tell es-Safi, and dated to around 850 B.C.E. The most recent remains were from the early Persian period, around 500 B.C.E., and were excavated at Ramat Rahel, which was an important administrative center near Jerusalem. 

In the pottery from all the sites, the scientists identified yeast strains associated with the production of alcoholic beverages: beer in most cases, and mead at Ramat Rahel. Genome sequencing showed that most of the strains are still commonly used in the production of traditional beverages in Africa, says the article in mBio.

Yeast older than the pyramidsIsrael Antiquities Authority, YouTube

For example, the Ramat Rahel yeast is similar to the strain used to make tej, the traditional Ethiopian honey wine. The exception to this African link was found in one of the Philistine ceramics from Gath, which was shown to contain Saccharomyces cerevisiae, today the most commonly used species of domesticated yeast in the beer, wine, and bread industries.

Philistine beer was wonderful

But how do we know that the little fungi actually descended from yeasts used by the Egyptians or the Philistines and weren’t from a later contamination of the vessels?

The researchers were encouraged by the results from their control group, which sampled pottery and other remains not thought to be associated with alcoholic beverages. Out of 21 alcohol-related samples, six yielded yeast strains. Out of 110 control samples, only two contained yeasts, from strains commonly found in the soil and not linked to alcohol production.

But the proof is always in the pudding – or, rather, in the booze – which is why the scientists decided to see if the age-old yeasts could actually make beer.

Food experts and experimental archeologists have often tried to reproduce foods and beverages of yore, but they usually use modern ingredients to prepare recipes gleaned from ancient texts or archaeological evidence at production sites, Hazan says. 

“As far as I know this was the first time that beer is made using the same yeasts that were in use thousands of years ago,” he says.

The researchers used a basic modern beer recipe, meaning the results probably did not taste exactly like the brews quaffed in antiquity, when it was common to add flavors and additives to the mix, explains Yitzhak Paz, an archaeologist with the Israel Antiquities Authority who took part in the project.

“In ancient Egypt for example they often added date or pomegranate juice to give it a sweeter, fruitier taste,” Paz says. “Still, most of the beers we made tasted very good.”

According to expert tasters recruited for the study, three brews made from the samples taken at En Besor, the Philistine city of Gath and Ramat Rahel all scored high marks. A fourth beer, also from Gath, had a “slight spoiled off-taste” but was still considered drinkable, the report in mBio says.

The researchers also looked for yeasts in glass bottles that were excavated at General Edmund Allenby’s army camp in central Israel used by the British during World War I. But here they came up with nothing because glass doesn’t have the same porous structure of ceramics that can make a comfortable home for these microorganisms, Hazan says.

Be responsible, give the baby beer

All this is fascinating, but how exactly does it help archaeologists?

First of all, we need to remember that in antiquity, alcoholic beverages were much more than the social lubricants they are today. Beer, in particular, was ubiquitous in the Levant, and was drunk by all, from babies to the elderly, often instead of water, explains Paz. At a time when most water sources could be dangerously contaminated, drinking a slightly alcoholic beverage was probably a safer alternative, he says.

Possibly a large percentage of ancient ceramics bear colonies of yeast or bacteria that were used to make not only beer but also other fermented foods, such as bread, cheese and pickles.

Studying these microscopic critters could provide us with new information on the diets of ancient populations, not to mention, which vessels were used for which purpose. Unless they were lucky enough to find residual foodstuff at the bottom of ancient pottery, such as in the recent case of the “oldest cheese in the world,” archaeologists have had to make educated guesses based on ancient texts – for periods after writing was invented – or their own hunches.

For instance, archaeologists have no idea what was done with giant basalt mortars over 11,000 years old found in Israel. They may have been used to grind grain. Or they may have been pounded to make a sound that would summon the tribe. Those are just two of the theories. 

And for dessert, studying and comparing the microbes that different ancient civilizations used to make food and drink could bring us new knowledge about the links between these cultures, their trade routes, and the exchanges of technologies and populations that connected them.

Yaniv Berman, courtesy of the Israel Antiquities Authority

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