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Dr. Rachel Lloyd: The Science of Sugar

A food chemist with a sweet legacy

Rachel is drawn looking off to her right. She's wearing a dress with a high collar and brooch. The background is a cloud of green, orange, and yellow. On the bottom right of the portrait is a sugar beet, and on the top left is a sucrose molecule.
Dr. Rachel Lloyd by Sachi Weerasooriya

Humans LOVE sugar. There’s something about that sweet taste that our brains just can’t get enough of – whether it’s in cold ice cream, melt-in-your mouth candies, or a rich, steaming cup of hot chocolate. It’s one of the fundamental tastes that our tongues can detect, so we’ve been trying to extract that flavor for almost the entirety of human history. For most of that time, the only ways to sweeten things that aren’t inherently sweet came from natural sugars like honey, or sugar extracted from a plant called sugar cane.

But did you know that you can also extract sugars from vegetables like the sugar beet? It’s a hard process – one that requires a lot of knowledge of chemistry and agriculture – and for a long time, scientists couldn’t quite figure out how to make it work in the US. This changed in the late 1800s, due in large part to the research of a chemist named Dr. Rachel Lloyd. Now, because of her discoveries, extracted sugar from sugar beets makes up a pretty big part of American agriculture. Let’s dive into the big ideas of food chemistry, sugar beets, and the sweet science that Rachel Lloyd uncovered along the way.

"The next time you pour sugar into a recipe, it might very well have come from a Nebraskan sugar beet – a tasty testament to Dr. Rachel Lloyd’s sweet legacy."

Watch the video or read more below!

Table of Contents:


The Science of Yummy Food

How can we tell if something is sweet? That may seem like an obvious question– just taste it! But when you think about it, our ability to taste anything at all is pretty awesome. With our tongues and taste buds, we’re able to detect thousands of microscopic chemicals and translate those chemical signals into the sense of taste. It’s usually easy for our brains to identify taste categories like sweet, salty, or savory. But it’s harder to identify the specific chemical structures that are interpreted by our brains as these particular tastes. There’s a whole research field called “food science” that studies this! Food scientists want to understand exactly how tastes depend on the chemical makeup and structure of food molecules.

When I say your food is full of chemicals, that might sound a bit scary, but in reality everything is made up of chemicals. A “chemical” is just a substance that contains a single type of molecule. And while the word chemical might make you think of test tubes in a lab filled with bubbling, neon liquid, chemicals aren’t necessarily synthetically made. For example, water is a chemical made up of the molecule H2O. So how do we know exactly what chemicals are inside the foods we eat? Can we use chemistry to detect the molecules that our brains are so good at interpreting? Could we even use chemistry to make our foods taste better?


A Chemical Reaction

These are the kinds of questions that chemists in the late 1800s were trying to answer, including a chemist named Rachel Lloyd. Rachel was born in 1839 in Ohio, and she wasn’t always interested in chemistry. It wasn’t really until she was 20 years old that she started learning about the field from her husband, Franklin Lloyd. Franklin was a chemist and he set up a chemical laboratory in his home, which Rachel credited for sparking her love of the field. Tragically, her husband died only six years later, when Rachel was only 26. After that, she decided to use her newfound love of chemistry to support herself. For a long time, she taught science, chemistry, and pharmacology – the study of how different chemical drugs affect the human body – at schools across the US.

She learned a lot from her late husband, but Rachel also worked hard to further her chemistry education. She took classes during Harvard University’s summer sessions (since, as a woman, she wasn’t allowed full admittance at the school). She pursued her own chemical research, and in 1881 she became the first female chemist to publish research in a major chemistry journal. Rachel was determined to get her doctoral degree in chemistry, but no institutes in America would grant a PhD to a woman at the time. So she enrolled at a school in Europe and got her degree in 1887, becoming the first American woman and second woman in the world to do so!


Sugar Beets - Sweeter than Honey

After Dr. Lloyd got her degree, she was invited to teach at the University of Nebraska’s brand new chemistry department. There, she decided to focus her research on a new crop in the American Midwest: sugar beets! Since around the 1700s, people had been trying to extract sucrose (a sugar) from these vegetables by chemically separating the sugar from the beets’ pulp. In America, the crop had been introduced primarily by abolitionists as an alternative to sugar cane crops grown by enslaved people in the West Indies. But beet sugar had so far been a commercial failure in the US. The process for extracting the sugar didn’t work well, which gave it a bad taste, and poor agricultural practices often caused the beet crops to fail.

Sugar beets contain a large amount of sucrose (a sugar)

There are a lot of different chemicals that make up the food we eat, including carbohydrates, fats, and proteins. Sugars fall into the category of carbohydrates, which are molecules that are made of long chains of carbon, hydrogen, and oxygen atoms. Plants (like sugar beets) generate carbohydrates to use as fuel for themselves or as building blocks for their cells, and the only carbohydrate made by an animal is lactose, which is in milk. Usually the carbohydrates in our foods come in the form of starches, sugars, and fibers. These are more complex molecules that our body then breaks down into simpler molecules, like glucose, so that we can process them for energy. In the case of sugar beets, a chemical process is necessary to break the complex carbohydrates into the simple, sweet sucrose molecule, which includes soaking the beets in water, adding in calcium hydroxide, and crystalizing the extracted sugar.

So Dr. Lloyd began research to try to figure out the best ways to grow strong sugar beet crops to extract the most sugar out of them. To figure out the best farming conditions for the beets, her students and collaborators sent seeds to farmers all across Nebraska and asked them to send back the beets they grew. She and her students tested those beets’ sugar content to see how it depended on the growing conditions the farmers used. Dr. Lloyd and her students looked at over 700 different samples of beets, comparing four distinct species and a huge number of different soil and climate conditions.

Historic saccharometer (photograph by Mike Peel)

To measure the beet sugar content, Dr. Lloyd used something called a saccharometer. The saccharometer is a weighted glass bulb with a long thin tube, and it uses buoyancy to measure the sugar content of a solution it’s floating in. Dr. Lloyd would extract the sugar from the beets, dissolve this sugar in a set amount of water, and then submerge the saccharometer in the sugar solution. With the instrument calibrated properly, Dr. Lloyd could figure out the exact sugar concentration based on how high the bulb was floating in the solution. Saccharometers are very sensitive instruments, and are actually still used today to figure out the sugar concentration in things like wine and ice cream.


Whatever Floats Your Boat

Have you heard of buoyancy? It’s literally what floats your boat… and your balloon, and Dr. Lloyd’s saccharometer. Humans have always experienced buoyancy, but the Ancient Greek mathematician Archimedes (287-212 BCE) discovered how to measure it precisely. When you submerge an object in fluid (could be air, water, or any other liquid or gas), that object forces the fluid out of its way. We say that the object has displaced the fluid, and the amount of fluid displaced is equal to the volume of the object doing the displacing. Archimedes’ principle says that the buoyant force on an object is equal to the weight of the fluid displaced by the object:

where ρ is the density of the fluid (mass divided by volume), V is the volume displaced, and g is the force of gravity. So ρ x V x g is exactly the weight of the displaced fluid. The buoyant force acts in the direction opposite to gravity. If the buoyant force is less than the weight of the submerged object, then the object will sink through the fluid. However, if the buoyant force is exactly equal to the weight of the object, then that object floats!

What if the buoyant force is greater than the weight of the object? In this case, the buoyant force will push the object out of the fluid until the buoyant force and the weight are exactly equal. By pushing the object out of the fluid, the displaced volume V gets smaller, and so does the buoyant force. This is how objects can float on top of a fluid, or partially submerged.

The saccharometer is a carefully calibrated instrument that is designed to be the exact density of plain water. Changing the density of the fluid it’s floating in (ρ, in our equation for the buoyant force) will therefore change the magnitude of the buoyant force. The saccharometer’s position in the fluid will change (rising out of the water or sinking lower) based on any small change in the density of the fluid. Based on the equation for the buoyant force, will a denser fluid make the saccharometer float higher or lower?


Nothing Beats a Beet

Dr. Lloyd’s research group found that by using the right species with careful farming techniques, sugar beets could be a successful crop in the region to produce high quality (and sweet!) sugar. After these findings, the sugar beet industry in Nebraska grew substantially, and by 1899 there were already three beet processing factories in the state. In 1890, Nebraska produced around 700,000 pounds of granulated sugar; just 5 years later, in 1895, it grew to over 8 million pounds! Beet sugar manufacturing is still a major industry in Nebraska today, and Dr. Lloyd’s contributions had a major and direct impact on this industry and agriculture more broadly.

Food science and chemistry have come a long way since the 1800s– we now have chemicals that can produce almost every flavor imaginable, artificial sugars that taste almost as good as the real thing, and complex food molecules produced entirely in a lab. Despite these impressive advancements, most American-made sugar is actually from sugar beets, made possible because of Dr. Rachel Lloyd’s research. In fact, most white sugar sold in grocery stores isn’t labeled by the plant that it came from. This means that next time you’re pouring sugar into a recipe, it might very well have come from a Nebraskan sugar beet – a tasty testament to Dr. Rachel Lloyd’s sweet legacy.

Written by Mark Griep and Caroline Martin

Edited by Ashley Cavanagh

Illustrations by Taylor Contreras

Portrait by Sachi Weerasooriya

Sources and additional readings:

Dr. Rachel Lloyd's legacy from the University of Nebraska Foundation

Rachel Lloyd from Wikipedia


Let’s dive deeper into the sweet world of food chemistry

Experiment (20-30 minutes): Rachel used buoyancy to measure the sugar concentration of different foods, and you can too! Use this at-home experiment to learn about why things sink and float, and use that knowledge to calculate the densities of different foods around your house.

Make (15-20 minutes): When you toast a marshmallow, why does it get tastier as it gets browner? The answer is through a chemical process called the Maillard reaction. Learn about this chemical reaction by making a secret message hidden in the marshmallow, only revealed with chemistry!

Taste (15-30 minutes): Your mouth is an amazing, delicate chemical detector, and it can also be part of your home laboratory! Experiment with different combinations of acids and bases (all with edible chemicals) and how those chemicals affect your sense of taste.


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