What Makes Sugar Sweet?

Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov
Sugar cubes.
Sugar cubes.

The human tongue responds to a range of different substances, registering them as various tastes. Evolution programmed our gustatory sense to find nutritious things tasty, and un-nutritious things un-tasty — for the most part. Human beings are flexible about what they eat relative to many animals, hence our omnivore status, but there are many types of organic material that we are incapable of digesting, and hence perceive as unpleasant. Sugar is highly digestible and offers a very condensed source of calories, so to us it tastes good — and has a distinct flavor that we label sweet. All mammals, except cats, can taste and enjoy this substance and are more inclined to eat poor-tasting food if it contains some.

Mammals are programmed to eat unhealthy foods if they have a sweet taste.
Mammals are programmed to eat unhealthy foods if they have a sweet taste.

Scientists now know that the tongue is covered with tiny clusters of chemical sensors called taste buds. It is the geometric shape of incoming molecules that determines how they taste. Some foods have multiple molecules that all contribute to their overall taste sensation. There are several types of sugar that exist, but by far the most frequently consumed by humans is a molecule called sucrose. There are also other molecules, like saccharine, that taste sweet even though they aren't sugar, although the taste sensation is slightly different.

Chemical sensors called "taste buds" sense the sweet molecules as they enter the mouth.
Chemical sensors called "taste buds" sense the sweet molecules as they enter the mouth.

The reason that two different classes of molecule produce the same sweet taste was confirmed in the 1960s. They both have a dual set of hydrogen atoms poking out from their surface like a prong, ready to bond with receptors in the tongue. In sugar, these two atoms are between 2.5 and 4 angstroms apart, where an angstrom is a length approximately equal to the width of two hydrogen atoms. Saccharine has an entirely different molecular structure, but the same prongs with similar spacing, leading to a similar taste sensation.

Cats don't taste sweetness.
Cats don't taste sweetness.

Bitter-tasting substances also have two hydrogen atoms sticking out for bonding, another prong, but the average separation of these two atoms is 1.5 angstroms. The different spacing of hydrogen atoms by a mere few atomic diameters is enough to produce the high level effect of either sweetness or bitterness. That is why sugar tastes sweet, and quinine tastes bitter.

Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

You might also Like

Readers Also Love

Discussion Comments

anon322546

Really, I didn't knew cats can't taste sugar.

ddljohn

@turkay1-- The surface of our tongue has many taste buds. These buds come in different shapes. Some are made to detect sweet, while others taste sour, spicy, bitter and so forth.

Each flavor has a different shaped molecule. It's kind of like the shape game we all played as kids. Each molecule fits into the taste bud on our tongue that matches its shape. Once this happens, the sensory nerves send a message to our brain which tells it what the flavor is. So if the sweet taste bud is filled with a molecule, our brain gets the message that we're tasting something sweet.

With the sweetener you're talking about, I believe the molecule structure of sugar is changed so that the calorie content is removed but the molecules that identify flavor on our tongue remain. So we still taste sweet but our blood sugar levels are not affected.

burcidi

Fructose-- the sugar found in fruit-- tastes sweeter and better than table sugar or sucrose to me. Why is this?

How is the composure of fructose different than sucrose?

What about honey? Honey tastes sweeter than sucrose too. Lactose on the other hand, the sugar in milk products don't taste as sweet.

candyquilt

Isn't there a new calorie free sugar substitute on the market that's made from sugar, but it's not quite sugar?

How do they make this and still retain the sweetness of sugar?

Oceana

So, sugar's sweetness is actually dependent upon the receptors of the tongue receiving it. It's kind of like the question of whether or not a tree falling in the forest makes a sound if no one is there to hear it. Is sugar actually sweet if the animal ingesting it can't sense the sweetness?

Perdido

I had never thought about sugar being a concentrated form of calories, but it definitely is. It makes sense that we crave it so much now.

I have a bad addiction to sugar cookies. Once I start eating one, I can't stop at just one or two.

The craving is worse if the sugar cookies are topped with either sweet icing or colored grains of sugar. The more sweetness in the cookie, the more I want it.

lighth0se33

@JackWhack – Dogs have more taste buds than cats, though they do have less than humans. I've read that they can taste sweetness, probably because wild dogs sometimes have to eat fruit when there isn't enough meat to survive on.

My dogs love watermelon. I've even seen them eating blackberries right off the vine.

This taste for sugar can be harmful at times, though. I've heard that antifreeze has a sweet taste, and that is why dogs are drawn to it. Never let your dog come in contact with the stuff, because it will kill him.

JackWhack

It's kind of sad to me that cats can't taste the sweetness of sugar. However, it probably isn't good for them anyway, so this might be a good thing.

Can dogs perceive sweetness? Do they like eating sweet things?

anon290776

My cat has recently been diagnosed with cancer and the vet says she will die within the year. I was wondering if it was at all possible to let her taste sugar just once before she finally dies; it's on her bucket list.

anon286161

So, why does sugar taste sweet?

anon198375

If this article leads you to wonder what the natural diet for humans is, then read the book 80/10/10 by Douglas Graham.

wizup

@anon21306 - That's a very good question. Splenda is a sweetener with no calories, unlike our regular sugar's calories. Splenda consists of dextrose, maltodextrin, and sucralose. It gets its sweet taste from sucralose which is 600 times sweeter than real sucrose.

The ingredients in the little pink packets of Sweet N Low are dextrose, soluble saccharin, and traces of anti-caking agents. This mixture is 300 times sweeter than real sucrose but leaves a bitter taste in your mouth.

Sweet N Low is a popular artificial sweetener but it cannot be used for baking because saccharin becomes unstable under heat.

Splenda is often the preferred sweetener for sugar free desserts because sucralose remains stable in both hot and cold conditions.

anon21306

What makes artificial sweeteners taste so much like real sucrose? What molucule creates the sweet taste in Splenda and Sweet'N low?

anon3490

Its great work. I would like to congratulate you on this tremondous task undertaken.

My Question:-

What r alkaloidal reagent & why they named so?

Post your comments
Login:
Forgot password?
Register:
    • Sugar cubes.
      Sugar cubes.
    • Mammals are programmed to eat unhealthy foods if they have a sweet taste.
      Mammals are programmed to eat unhealthy foods if they have a sweet taste.
    • Chemical sensors called "taste buds" sense the sweet molecules as they enter the mouth.
      Chemical sensors called "taste buds" sense the sweet molecules as they enter the mouth.
    • Cats don't taste sweetness.
      Cats don't taste sweetness.