Preservatives: From honey-covered berries to plastic-wrapped Twinkies

Tiny Matters

Humans have been finding ways of preserving food for thousands of years—long before the invention of silica gel packs that absorb moisture or chemicals that keep away bacteria and mold. This week’s Tiny Matters is about the evolution of food preservatives and additives and the regulations that came about to keep us safe from the more dangerous ones we came up with (ahem, arsenic candies).


Transcript of this Episode

Sam Jones: Humans have been finding ways of preserving food for thousands of years. And that need only grew as we left more nomadic lifestyles behind, settled into communities, and started farming and harvesting food, which meant we needed to find ways to keep that food from spoiling.

This was a time long before silica gel packs that absorb moisture, or chemicals like sodium benzoate that keep away microbes like bacteria. It was a time where we didn’t even know that bacteria could spoil food, or that bacteria were a thing at all.

So, what did we do to keep our food edible? I mean, whatever we did, it had to have worked decently well because… we’re still here.

[intro music]

Sam: Welcome to Tiny Matters, I’m Sam Jones and I’m joined by my co-host Deboki Chakravarti.

Deboki Chakravarti: Today’s show is all about food preservation—what it is and why it’s important, and its sometimes problematic history. We’ll also talk about preservatives in a context that’s not food-related.

Let’s start by tackling some of the basics.  

For most foods, if you don’t preserve them they’ll spoil pretty quickly. That’s generally because the chemical compounds that make up food will react with things in the environment—like moisture and air—causing the food to break down. We also live in a sea of bacteria and yeast and mold and many of those will go after your food if you don’t get to it first.

Sam: For example, the mold Penicillium expansum secretes a molecule called patulin, which reacts with proteins in fruit cells, destroying them and leaving you with a smelly, fuzzy-looking pile of mush. This is just one example, but there are tons of them.

Being able to preserve food so that it didn’t turn into a fuzzy-looking pile of mush was unbelievably important for our species to survive. It allowed us to harvest a bunch of food all at once and keep it around, so in times when there wasn’t as much food available we wouldn’t immediately starve.

Deboki: So let’s talk about the ingenious preservation approaches of our ancestors. Some may not sound wildly exciting or inventive compared to preservative approaches today, but I think we don’t give the humans who lived thousands of years ago enough credit for how much they figured out with so few tools available.

I think a fun one to start with is honey. Preservation with honey was big. Tons of ancient civilizations like the Greeks, Romans, and Chinese got on the honey bandwagon to preserve a bunch of foods, often different fruits. And word has it that when Alexander the Great died, he was temporarily embalmed in honey so that his corpse could make it back home to rest without turning into human sludge.

Sam: Nice. That’s a nice image. I actually tried using honey as a preservative once—not for a human corpse but a strawberry—and it worked unbelievably well. Over a month after completely covering a strawberry in honey it looked a little dehydrated, but there was no visible mold or bacterial growth.

Alright, so how does it work? Honey keeps food from rotting because it is super high in sugar. Sugar attracts water molecules, keeping them away from microbes like yeast and bacteria that need water to survive. Today some people may still preserve food in honey for the taste, but lately I’ve been seeing people using honey to ferment different fruits and vegetables. Which brings us to our next food preservation method that has been around a very long time as well: fermentation.

So fermentation is a process where carbohydrates like starch are broken down by bacteria and yeast. Fermentation is of course used to make beer because, depending on the ingredients used and how long you leave it for, you can get a lot of alcohol from it. But fermentation is also used in foods like kimchi, sauerkraut, kombucha, and yogurt.

Deboki: Like Sam said, fermentation is ancient, but drying food to preserve it is likely even older. Some researchers think that as far back as 12,000 BCE people in the Middle East and Asia were drying foods in the sun.

A process called curing did something similar—it removed water—but by using salt, not the sun. And in the 1800s people realized that  using saltpeter, which is actually potassium nitrate, for curing gave meat a reddish-pink color—the color of a hot dog—and not the typical gray color you’d get from coating things with table salt.

Years later, people learned that nitrates don’t only keep things looking more appetizing, they stop the growth of a super dangerous bacterium called Clostridium botulinum, which produces botulinum toxin—one of the deadliest compounds on Earth.

Sam: Deboki and I talk about botulinum toxin and the fact that it’s the active ingredient in Botox(!) in Tiny Matters episode 6, which is all about bioterrorism. So if you want to learn more, go listen to that. What you need to know about botulinum toxin in this context is that it stops your neurons from signaling to each other, leaving you paralyzed. The first symptoms of botulism often show up in someone’s face, as muscles that control their eyes and mouth begin to weaken. That paralysis spreads further down their body, eventually damaging muscles they need to breathe.

You usually hear about botulism in the context of canned goods. Canning is a much more recent way of preserving food compared to honey, drying, curing, or fermenting.
With canning, foods are placed in jars or…cans… and then heated to a temperature that destroys microorganisms and other things that could either make it rot or be dangerous. As the can cools it forms a vacuum seal which prevents anything from getting in. But if there is damage to a can, even a tiny opening could allow Clostridium botulinum in. And—unlike many bacteria—it thrives in low oxygen environments, so it can quickly grow and produce its deadly toxin.

Deboki: Canning was developed in France during the Napoleonic Wars, when France was trying to take over much of Europe. It’s more complicated than that, but totally irrelevant to canning so we’ll move on. In 1795, Napoleon Bonaparte offered a bunch of money for the invention of a food preservation method that could sustain large quantities of French troops that were both on land and out at sea.

In 1809, a guy named Nicolas Appert ended up winning that money which, if we take inflation into account, would be around 300,000 dollars today. Appert had discovered that applying heat to food in sealed glass bottles kept the food from deteriorating. And, in 1810, a guy in England named Peter Durand applied that method with tin cans.

Sam: There have been a lot of other preservation methods over the years, but the last one we’ll mention before we talk about more recently developed methods is freezing. In certain climates it was, of course, very easy to preserve foods through freezing. You could just… leave them outside. People would also use cellars and caves that were naturally very cold to keep food from rotting.

In the US, there were buildings called ice houses, and then you had smaller versions of this called ice boxes. But then more modern refrigeration was invented in the mid-1800s. Then in the late 1800s, quick freezing was discovered by Clarence Birdseye. He’s considered the founder of the modern frozen food industry and actually started the company Birds Eye. I definitely have Birds Eye frozen peas in my freezer right now.

So you might be wondering how society went from fermenting and drying things in the sun to canning to… candy bars and plastic wrapped Twinkies that can sit out on store shelves for months or even years.

It was during the Industrial Revolution, around the early 1800s, when the use of preservatives really took off. Scientists were learning how to synthesize different chemicals, leading to an explosion in the use of things like artificial thickeners and flavors and colors. But everything was so new—their toxicology and other safety implications were mostly unknown. For instance, red lead was used to make bright orange cheeses, and sweets were colored a beautiful greenish-turquoise using arsenic.

Sam: If you couldn’t already tell, there was little to no regulation when it came to what was in the stuff people ate. On top of that there were meat-packing plants that were super unsanitary and a flood of cure-all claims circulating for different medicines that either did nothing or were incredibly dangerous. But as we approached the 1900s that all started to change. For a lot of reasons.

In 1905, Upton Sinclair exposed a lot of these problems in his novel The Jungle, which he first published in serial form in Chicago’s socialist newspaper at the time called Appeal to Reason. People were understandably upset. And that combined with advocacy from scientists like chemist Harvey Washington Wiley, prompted Congress to establish some sort of responsibility for public health.

Deboki: They soon passed the Pure Food and Drug Act of 1906 which prohibited the sale of misbranded or adulterated food and drugs, and laid the foundation for the Food and Drug Administration aka the FDA. And in 1907, the first certified color regulations went into place, and seven colors were designated as being suitable to use in food.

These were no doubt important steps forward, but there was more work to do. For one, the law was lacking in specific standards for food. You could buy something that had “strawberry spread” on the label but that didn’t have any actual strawberries in it, but it did have seeds from hay thrown in to make it look like there were strawberry seeds in that spread. Or you could buy something called peanut butter that maybe had a few peanuts in it but that was mostly lard.

Sam: And the deceptive packaging was… impressive. Your had jars of chicken were sold with the white meat lining the jar, hiding the dark meat, lower-quality chicken in its interior. There were boxes of chocolate had false bottoms that made it look like you were getting way more chocolate than you actually ended up with.

Deboki: That one cuts deep. I would be so mad if I bought a box of chocolate and then realized there was a fake compartment in there to trick me.

Sam: Fair. It’s pretty upsetting. So chocolate—big issue. Potentially a bigger issue: the total lack of regulation for cosmetics. Things like hair removal cream that might make you lose your teeth and mascara that made people go blind. Those could be sold legally under the 1906 Pure Food and Drugs Acts.

So in 1933, to illustrate the need for a new law that would increase regulation of food and drugs and include cosmetics, the FDA assembled a bunch of the problematic products in an exhibit, initially just for Congress to see. Soon, the exhibit was open to the public as it traveled around the country. It was even at the World's Fair in Chicago. A reporter accompanying First Lady Eleanor Roosevelt during her tour dubbed it The American Chamber of Horrors. The name stuck.

Deboki: And so, in 1938, the Food, Drug and Cosmetic Act went into effect. It established quality standards for food, drugs, medical devices and cosmetics manufactured and sold in the United States. And it provided federal oversight and enforcement of those standards. This law still protects us consumers today, although it’s now been amended dozens of times. For instance, in 1958 you had the Food Additives Amendment, which requires manufacturers of new food additives to establish safety before they could be used.

Sam: Seems like should have always been the case, but OK.

…Yeah. And there have also been amendments tightening regulation of infant formula, dietary supplements, and so much more.

Sam: When I was doing research for this episode I was actually kind of blown away by how little ingredients, including preservatives, used to be regulated, particularly in cosmetics. Maybe because I don’t think about preservatives in that context. So, to learn more about that, we reached out to chemist Kelly Dobos.

Kelly Dobos:
I think a lot of people have an impression that cosmetics aren't regulated by the US FDA, but they certainly are.

Sam: Kelly is an independent cosmetic chemist consultant and a visiting professor teaching color cosmetics at the University of Toledo.

Kelly Dobos: A cosmetic doesn't need to be sterile per se—it's not going to be something like a drug product where it has to be completely free from bacteria—but it should be free from pathogens. And then the concentration of non-pathogenic bacteria should be low.

Deboki: So there can’t be any dangerous, or pathogenic, bacteria in or on a cosmetic product, and even with non-pathogenic microbes there are very specific limits. So when chemists are deciding what preservatives to use they need to consider the microbe or microbes that would be trying to colonize whatever product it is.

Kelly Dobos: So we've got gram negative bacteria, gram positive bacteria, and then we've got yeast and molds to worry about. So we are going to look at ingredients that have a known safe history of use that are also safe for skin. We also look for materials that have low allergenic potential.

They also have to be compatible the cosmetic’s pH, and with the other ingredients in the cosmetics—sometimes cosmetic ingredients can inactivate certain preservatives. So there's a lot of research involved in selecting the right preservative package for a cosmetic.

Deboki: When you think of something like eye shadow or face lotion, you might not immediately think, “I need to keep bacteria from growing in this!” but thankfully chemists like Kelly are on top of it. And when we chatted with her, she reminded us of another important factor to consider with cosmetics: how long you keep them around.

Kelly Dobos:
Food, you have the benefit of refrigeration or a much shorter shelf life. But a cosmetic–we're looking to have that be stable on the shelf for, you know, two to three years.

Kelly Dobos: Throughout the process of cosmetic product development, we are testing to prove that our preservative will last throughout the life of a product. We want to show that two to three years that that product is safe on the shelf, but also in consumer use. So we have preservative efficacy tests where we emulate cosmetic use or consumers inoculating the product with bacteria. So imagine you have a skin care cream that comes in a jar, you're touching it with your fingers, which of course are the most diverse microbial habitat you have on your body. So we try to simulate that kind of scenario in our product development testing to determine that we have an adequate preservative system and that it would last through that type of insult by the consumer.

Sam: Just like finding the right preservatives that keep your food from spoiling, the same needs to be done with cosmetics. I won’t look at a tube of lipstick the same way ever again.

Deboki: Me either.

Sam: And I definitely have some makeup sitting around that’s like 7 years old and I should probably throw it out…

Sam: Okay, so Tiny Show and Tell Time.

Deboki: Yeah.

Sam: I can go this time?

Deboki: Yes, yes.

Sam: Yeah. Why not? Okay. I'm going to be talking about wine. When you go into a liquor store, grocery store, whatever it may be. You see some wine on the shelves. You probably notice that a lot of those bottles are colored, a dark green or blue, or they're not clear for a lot of wines. That is actually on purpose. It's not just fancy. It's actually on purpose because when there's this chemical reaction in wine called, light-strike, the wine will actually start to produce a bunch of kind of gross odors, including sauerkraut, marmalade, maybe marmalade wouldn't be terrible, but wet dog is one of them. They're really just a huge range. And I don't know about you, but I don't want to drink wine that smells like wet dog.

I have two dogs and I know that smell and it's not good. So even though light-strike is something that people have known about for at least 50 years, winemakers, scientists, they just weren't really sure how fast it was happening under different conditions. And so this group of researchers actually stored more than a thousand bottles of wine in an imitation grocery store to try and understand the effects of shelf storage. So ultimately what they were able to do was they were able to hone in on different chemical changes throughout that time. And they were able to see that the clear bottles, you are getting tons of chemical changes, even within just a couple of weeks.

Sam: So if you go pull a rosé or a white wine off of a shelf where it's been under fluorescent lighting for a couple of weeks, you're already going to be getting the effects of those changes, those chemical changes. Whereas, wine that was in green bottles, didn't exhibit the same kinds of chemical change, even after over 50 days on a shelf. Any wine that seemed to be stored out of the light at all was pretty stable. I was interested in this story because of the headline that it had, which was, "Don't let your wine go to the grocery store naked."

Deboki: That's amazing.

Sam: I'm probably going to think twice before I pick up a bottle of wine, that's in a clear bottle, versus one that is a darker color. And it's hard because with things like rosés, apparently people like to see the color of it before they get it. But if you're going to a place where there isn't really fast turnover of purchasing of wines, there's a really good chance that you might pick up some of those wet dog smells. So that's my Tiny Show and Tell today.

Deboki: That's amazing. Do you know, there's a chemistry reason for why some beers are in green bottles as well, right?

Sam: Yes.

Deboki: Is it related to this?

Sam: Yeah, I think so. I don't know if it's this thing light-strike. I wouldn't be surprised if it is, this is just kind of an example of trying to understand more of the science behind something, to allow manufacturers and people who are selling wine to be able to put their wine in bottles that will actually keep for longer. It's less wasteful. People are getting better tasting wine. Feels like a win-win.

Deboki: Yeah. And I just love the idea of an experimental space designed to look like a grocery store.

Sam: I know, it's amazing.

Deboki: We're we got to build our simulation grocery store, you guys.

Sam: So Deboki, you ready? Do you want to do your Tiny Show and Tell?

Deboki: Yes. Yes. I will do my Tiny Show and Tell and I think it'll be emphasis on the tiny, because today I'm more in my mode of recommending an article that I just want a lot of people to read, just because I liked what it made me think about. So this was an article in Undark, called, What Menstrual Blood Reveals about Health and Disease. I just really enjoyed this article because I thought it was a really interesting exploration of, A, menstrual blood, potentially a very good source of health information, but also B, not a lot of people studying it for reasons that maybe seem actually kind of obvious, which is that ... and maybe if you're a listener or maybe you like have had this reaction of you hear menstrual blood and your immediate response might be just, "Ew." Who wants to handle people's menstrual blood, who wants to be sending in samples of their menstrual blood?

But as the article points out, it's kind of funny, because we study plenty of gross fluids from people's bodies. Poop is a thing that people have been studying for a very long time. Like it's not like we don't study gross things and get a lot of really valuable data out of it. And menstrual blood has a lot of potential advantages for different diseases, or for understanding different things about people's bodies. And this article is really diving into the ways that different people are, even though it's a small group, how there's really this kind of diverse array of ways that people are looking at menstrual blood. There's people who are looking at menstrual blood as potentially a way to diagnose endometriosis. It's one of those diseases that people have a really hard time getting a diagnosis for, just because it's hard enough to get people to take their pain seriously.

But also the diagnosis process is pretty invasive and it's pretty intense. So if we can use menstrual blood to diagnose endometriosis, the idea is that we might be able to get people their diagnoses faster and get them their treatment faster. There's also someone else who's looking at menstrual blood as a way to understand how the environment might impact people's reproductive health. But that's why I wanted to talk about this article and want to get other people to read it. Because even though a lot of these studies are very early stages and whether or not they're going to give us these new ideas and techniques, we've got a long ways before we're going to get there. I think it's worth thinking about.

Sam: That's so interesting. And you know, like you mentioned, there are so many other things that are "gross" that we study. I mean, fecal transplants and conversations around fecal transplants have been around for decades at this point. But then when you say something like menstrual blood, the immediate response is not always a positive one and people being really kind of weird and cagey around it. So I think the more people that are aware of this kind of research and how important it could be, whether it's for diagnosing endometriosis or maybe other things that might be going on, it feels like there could be so many really important implications of this. And I think the way that we're going to get to the point where it actually goes from experimentation phase to actual diagnoses for people, there have to be people on board.

And so, reading an article like this, feels silly to say humanizing it, but it really is this thing that I think people are just so repulsed by overall. And that's a societal thing that's not ...

Deboki: Yeah.

Sam: You've got approximately half of the people under age, whatever, 45 are experiencing this monthly. So, it's very much the reality. So how can we help all of those people? These kinds of topics make you really think a lot about why you feel a certain way and who told you, you should feel that way. So thanks Deboki, this is really cool. I'm excited to read it.

Deboki: I hope other people are excited to read it too.

Sam: I think so.

Thanks for tuning in to this week’s episode of Tiny Matters, a production of the American Chemical Society. I’m your exec producer and I’m joined by my co-host Deboki Chakravarti.

Deboki: This week’s script was written by Sam, edited by me and by Matt Radcliff who’s the Executive Producer of ACS Productions. As always, it was fact-checked by Michelle Boucher. The Tiny Matters theme and episode sound design are by Michael Simonelli and our artwork was created by Derek Bressler.

Sam: Thanks so much to Kelly Dobos for chatting with us.

Deboki: Sam and I are planning to do a Q&A episode in the next couple of months so please send us question–science questions, questions about the podcast, questions about us. We want to hear from you!  

You can find me on twitter at okidoki_boki

Sam: And you can find me on twitter at samjscience. We’ll see you next time.



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