If you were invited to a  dinner party in Ancient Rome, the spread might have looked a  little bit like what you’d find in your friend’s apartment today:  bread, cheese, honey, some wine.

But there might have been some  other delicacies that felt more… unorthodox to our modern palates. Like roasted pig udder or nut-fattened  dormice—the rodent cousins of mice.

But no matter which dishes were on  the buffet, every Ancient Roman chef almost certainly had a not-so-secret  sauce in their kitchen called garum. Garum is a fish paste made by  fermenting whole fish or fish guts under the hot sun in barrels full  of salt and other seasonings. From what we can tell based on  recipes and other writing from across the centuries, garum was used by all  social classes in sauces and dips.

Despite its pungent odor, it was  widely beloved for its unique taste. And modern researchers have been hungry to know what was so special  about this ancient condiment. [♪ INTRO] For the scientists and historians  who wanted to recreate garum, their first hurdle was  figuring out what it even is. Food historians have traced  references to a stinky fish sauce across countless texts in Greek and Latin.

Mysteriously, they found several  different words that all seem to refer to the same sauce…or maybe  several variations of the sauce over time. See, there’s the Greek word  gáros, which may have originally referred to the specific fish  that was used for the sauce. And garum was the Latin counterpart that  Ancient Romans used and wrote about.

For example, Pliny the Elder wrote  about garum’s quote “exquisite nature” and “unpleasant smell” in  his text Natural History, describing how it was “prepared from  the intestines of fish and various parts which would otherwise be  thrown away, macerated in salt; so that it is, in fact, the  result of their putrefaction.” Pliny the Elder also wrote about  garum’s…uh…medicinal properties. He claimed it was a great treatment for  wounds like dog bites, ulcers, or burns. But, yanno, Pliny said a lot of things.

But there’s another word that was  used by later

Romans: liquamen. Liquamen may have been a  generic term for fish sauce, since it appears throughout a very  famous, very old Roman cookbook. Or liquamen may have referred to a liquid extracted during the garum preparation process. In any case, modern food  scientists mostly use “garum” to describe any and all of the  old, Roman, fermented fish sauces.

So that’s what we’ll call it in this episode, too. Now, garum isn’t special because  the Ancient Romans were somehow incredible geniuses who figured out  fermentation science for the very first time. Fermentation was already a well-established  food preservation technique, and cultures across Asia have been fermenting fish in various ways for hundreds  or thousands of years.

If you’ve ever cooked a  Southeast Asian dish at home, you might even have a bottle  of fish sauce in your pantry! Scholars aren’t sure if fish sauces in  Southeast Asia are derivatives of garum or were invented independently. But it’s no surprise that  fermented fish sauce caught on, because fermentation is an incredibly  cool and effective preservation method.

There are actually a couple different  kinds of biochemical processes that fall under the umbrella term of “fermentation.” But they have a key principle in  common: without oxygen around, some microbes can thrive and  break down food molecules, like proteins and carbs, into molecules  that we taste as unique flavors. But there are also microbes that break  food into compounds that can poison us. So fermentation is a game about  controlling the decomposition process so that we get something yummy and safe to eat, rather than an impending case of food poisoning.

To be fair to bacteria and fungi, they’re  all just trying their best to survive. But, for simplicity’s sake, because we’re  talking about food that humans prepare for humans to eat, we can draw a  line between “heroes” and “villains”. The microbes that don’t hurt us can  be considered “good” or “beneficial”, and the ones that can kill us are, well, “bad.” For example, some of the microbial good guys are Lactobacillus, or lactic acid bacteria.

They’re often found at the scene of  fermentation because they thrive in low-oxygen environments and  can withstand some saltiness. One of their main chemical  byproducts is lactic acid, which you’ll get whenever  carbohydrates are broken down into shorter sugar molecules  without getting oxygen involved. So you can thank Lactobacillus for  contributing to the tart and umami flavors in foods like pickles and  yogurt, as well as garum.

More importantly, lactic acid also  creates an environment hostile to many kinds of bad bacteria and fungi. As those good fermentation microbes  chomp their way through our pickle jars, they’re actively deterring other  organisms that could hurt us. Another way to control the  decomposition process is by adding salt— a crucial ingredient for  garum, you might remember!

Salt can inhibit some types of  potentially harmful bacteria, like E.coli, by limiting their water access. Too much salt, and the  E.coli dry out and collapse. Goodbye, tummyache!

Fermentation can break down the  carbohydrates in vegetables and in meats, but some Lactobacillus species are also good at breaking proteins into shorter amino acid chains! And that’s really important  when you’re fermenting fish, which are famously animals  with protein in their flesh. Basically I’m telling you that pickles  and pickerel can both be fermented by lactic-acid-producing bacteria!

But the exact species and macromolecules  involved are a little bit different. Fermentation is complicated  enough, but there’s an additional, extra weird thing going on  with fish sauces in particular. It turns out that the biochemistry of whole  fish fermenting is closer to the rotting end of the scale than your average pickle would be.

That’s because microbes  aren’t the only ones involved. See, for garum you usually just take  the whole fish, cover it in salt, and then stick it in a sealed container. Then any microbes that can survive  that super salty environment get to work breaking stuff down, but  the enzymes from within the fish’s own digestive system also catalyze  the protein-decomposition process.

This is a huge difference  because enzymes aren’t alive. Most of them are specialized  proteins that help kick off chemical reactions inside of living creatures. Normally they’re contained in cells or stick to certain areas of the body, like your gut.

But death makes everything…a little goopier. Before I tell you about the flavors  these fermentation processes create, I have a quick ad we’ve brewed  just for you, and it isn’t stinky. Thanks to CookUnity for  supporting this SciShow video!

CookUnity is a chef-to-you meal  delivery platform that connects you with hundreds of fresh, fully prepped  meals from award-winning chefs. I’m talking about over 130 chefs  across the country from the Food Network to James Beard Award  winners and Michelin-starred masters. And they cook all kinds of food.

With CookUnity, you can choose from  over 400 meals nationwide each week, including over 45 global cuisines and diets. With such a diverse selection  of global gourmet flavors, there’s something for every palate. We got cuisine from all over the world, from Cajun shrimp and kielbasa  pasta to barbecue chicken to pad kra pao with pork. …Which by  the way smelled and tasted amazing!

It was sweet and flavorful. Chef Stacy Bareng knew what they were doing. You can also personalize your  choices with options for keto, vegan, low-sodium, or high-protein meals.

CookUnity offers gourmet dining at  home with restaurant-quality meals by award-winning chefs,  delivered fresh to your door. All meals are handcrafted in small  batches in local kitchens near you. Then they’re delivered fully cooked,  so all you have to do is heat them up in two minutes or less, and you’re ready to eat!

They’re healthy meals without the  hassle of cooking or meal planning. CookUnity is offering our  viewers 50% off their first order when you click the link in the description  below and use the code SCISHOW50. Since the line between decay  and fermentation can be so fine, maybe it’s no surprise that this process can produce flavors that are intense  and…a little controversial.

Some amino acids that come from broken  down proteins are responsible for savory flavors, like salty,  buttery, and—sometimes—stinky. So garum and other fermented fish sauces are notorious for their funky, polarizing flavors. Dozens of Ancient Roman recipes  called for some kind of garum.

In fact, it was such a common ingredient  that there were words for garum mixed with other kitchen staples:  oenogarum was garum mixed with wine, oxygarum had vinegar, hydrogarum  had water…you get the gist. But just because it was popular, that  doesn’t mean it was universally beloved. I mean, look at mustard!

Psychologically speaking, the  feeling of disgust could warn us that something is unsafe for us. So an aversion to stinky foods  might be connected to an urge to avoid a rotten meal, or food that  made us sick the last time we ate it. But there are plenty of foods,  like a stinky French cheese, that aren’t dangerous for us to eat.

Their appeal is often precisely because they sit on the edge between disgust and delish. And the question of why some  foods taste good to us is a big, open question with lots of different hypotheses. Several groups of scientists have  proposed that savory or umami tastes could indicate the presence of nutrients, like  proteins and salts, that our bodies need.

But, unlike a nice, aged steak, the  question of umami can’t just be cut and dry. Some studies found that high-umami foods  might have both positive and negative health effects, including  better nutritional balance but also potentially increased headaches. Basically, nutrition is complicated!

We don’t need to solve all  of nutritional science today, but we do need to get back to the reasons  we do know fermentation is great for us. For one, fermentation helps us  preserve food for longer periods. Humans can’t always eat freshly caught  fish or ripe fruits and vegetables.

It’d sure be helpful to store up some  of those good proteins, sugars, fats, and other nutrients for later  in the year, like the winter. If you follow the right steps,  fermentation is a really reliable way to reduce the risk of bad microbes or  pests making your food inedible. Of course there are other food preservation  methods, like freezing or drying.

But fermentation’s superpower is that  it transforms the molecules inside food, making them smaller and easier  for our bodies to process. In a way, fermentation sort  of pre-digests our food before we ever put it in our mouths. And, depending on who you  are, that’s either the coolest or the grossest possible way  I could have phrased that.

This transformative power is  kind of why fermented foods and drinks have taken off  as modern-day “superfoods”. There’s evidence that fermentation  breaks down certain carbohydrates, proteins, and fats that would be  hard for us to digest on our own. With the help of fermentation, our bodies  absorb more nutrients from the food.

Plus, all that microbe and enzyme  action doesn’t just produce lactic acid and other substances that  inhibit bad bacterial growth… it also makes byproducts that  are beneficial in other ways. For instance, some species of  Lactobacillus can make B or K vitamins that we can’t make ourselves, or acids that help combat  inflammation in our immune systems. Some of the living bacteria themselves  could be considered probiotics, which can join—and even reshape—the  microbiome party in our guts.

All that to say, researchers aren’t just  interested in studying fermented fish sauces like garum because these condiments  were an Ancient Roman fad. Cracking garum’s composition  can also help us understand how our ancestors’ food technology  improved taste, safety, and nutrition. Although they’re probably partly  studying it because it’s fun and weird.

Listen, humans are gonna human. One research group recreated several  different versions of garum in the lab. Their recipes were inspired by six  surprisingly well-preserved samples found in buried vessels at a  garum shop in Pompeii, Italy.

The vessels were unearthed in the  1960s and have been studied ever since. Previous analyses of these trace  amounts of garum showed that it was probably made from anchovies, and the  presence of pollen indicated it might have been flavored with spices, such  as thyme, sage, fennel, and mint, which were common in recipes from the time. These researchers measured  the amino acids, fatty acids, and mineral content of the ancient garum, to serve as a benchmark for  their attempts to recreate it!

They composed their fishy brews  by layering whole anchovies, salt, and spices in a 5 liter vessel. To mimic a Roman garum vessel exposed to the sun, they kept the temperature pretty  constant at 50 degrees celsius. After 25 days of the fish enzymes  digesting through the goop, they mushed up the dissolved fish bones  and flesh into a fermented paste that, uh, looks about as good as it sounds.

But then they strained out the  solid chunks, leaving a transparent, stinky, fishy liquid that was  chockfull of glutamic acid— an amino acid known for its strong umami. With our modern understanding of fermentation, we can look back at recipes from the  past and see that our human ancestors were finding creative ways to  preserve food and make it tasty, with an added fermented-goodness  nutritional boost! Even if some of the medicinal claims of fish sauce may have been…a little far-fetched.

And not only do we have  evidence that Ancient Romans considered garum an essential condiment. But, now, we can taste it ourselves. Because beyond the lab, food  technicians have started to bring modern-day garum back to the public market!

They’re even making experimental  garum—or, I guess, just fermented sauce— out of other non-fishy things  like grasshoppers or bee larvae. Unfortunately I don’t have any to try here today… but with these modern garum recreations, that Ancient Roman-themed  dinner party could be way more authentic than I initially thought. So whether you love a funky  fish sauce or a tart kombucha, you're joining in a scientific and  culinary experiment that’s been bubbling away since before Ancient Rome — literally bubbling, in the sun, in  a barrel full of fish intestines. [♪ OUTRO]