What Type of Sugar is Cornstarch?

December 9, 2025 •

3 min read

Cornstarch is a pantry staple known for its thickening power, yet many people are confused about its classification. Despite being composed of sugar molecules, the question of "What type of sugar is cornstarch?" has a more complex answer than one might expect. It is not a simple sugar but rather a complex carbohydrate known as a polysaccharide.

Quick Summary

Cornstarch is a complex carbohydrate, a polysaccharide made from long chains of glucose molecules. This molecular structure, unlike the simple molecular makeup of sugars, explains why cornstarch is not sweet and requires digestion to be broken down into glucose for energy.

Key Points

Polysaccharide: Cornstarch is a complex carbohydrate, or polysaccharide, made of many glucose units linked together.
Not Sweet: Unlike simple sugars, cornstarch does not taste sweet because its large molecules do not fit into the taste receptors on the tongue.
Requires Digestion: The body must break down the long chains of glucose in cornstarch using enzymes, a slower process than absorbing simple sugar.
Functional in Cooking: Its polysaccharide structure is what allows cornstarch to act as a powerful thickening agent when heated, a process called gelatinization.
Energy Source: Although it isn't a sugar, cornstarch is broken down into glucose by the body and used for energy, just at a slower, more sustained rate.

Understanding the Fundamental Difference: Starch vs. Simple Sugar

To understand what type of sugar cornstarch is, one must first grasp the core chemical differences between starch and simple sugars. Both are carbohydrates, which are organic compounds containing carbon, hydrogen, and oxygen, but they differ significantly in their structure and properties.

The Chemistry of Carbohydrates

Simple Sugars (Monosaccharides and Disaccharides): These are small, simple carbohydrate molecules. Monosaccharides, like glucose and fructose, are single sugar units. Disaccharides, like sucrose (table sugar), are made of two sugar units bonded together. Their small size allows them to be absorbed quickly by the body, providing a rapid energy source and eliciting a sweet taste.
Complex Carbohydrates (Polysaccharides): Polysaccharides, like starch, are made of many sugar units bonded together in long, complex chains. In the case of cornstarch, these chains are made entirely of glucose molecules. Because of their size and structure, they do not dissolve in water or fit into the taste receptors on the tongue in a way that triggers a sweet sensation.

The Role of Starch in Plants

In plants, starch serves as an energy storage unit. This is why corn kernels contain such a high percentage of starch in their endosperm. When the plant needs energy, it can break down the stored starch into glucose. Humans utilize a similar process during digestion. Cornstarch is extracted from the endosperm of the corn kernel, resulting in a fine, white, and flavorless powder that is nearly pure starch.

How Cornstarch is Processed by the Body

Unlike simple sugars which are absorbed quickly, cornstarch requires a slower, more complex digestive process. The human body uses enzymes, such as amylase in saliva and the pancreas, to break down the long polysaccharide chains of cornstarch into individual glucose units.

This is why if you chew a starchy cracker for an extended period, it will begin to taste sweet—your saliva's amylase has had enough time to start breaking the starch down into simple sugars. The slower breakdown process means that the glucose is released into the bloodstream over a longer period, resulting in a less dramatic spike in blood sugar compared to consuming a simple sugar.

The Culinary Functions of Cornstarch

Cornstarch's unique properties, which stem from its polysaccharide structure, make it invaluable in cooking and baking.

The Science of Thickening

When cornstarch is mixed with a liquid and heated, it undergoes a process called gelatinization. The heat causes the starch granules to absorb water and swell, eventually releasing their long glucose chains (amylose and amylopectin) into the liquid. These molecules then form a mesh, or gel, that thickens the liquid. This is a key reason why it is used as a thickening agent in sauces, soups, and gravies.

Amylose vs. Amylopectin: Standard cornstarch is composed of both amylose and amylopectin, two different types of glucose polymers. The ratio of these two polymers affects the thickening properties. Amylose forms strong gels, while the branched structure of amylopectin contributes to viscosity and stability.

Comparison Table: Starch vs. Sugar


Feature	Starch (Cornstarch)	Simple Sugar (Sucrose/Glucose)
Chemical Type	Complex Carbohydrate (Polysaccharide)	Simple Carbohydrate (Mono/Disaccharide)
Molecular Structure	Long chains of glucose units	One or two glucose/fructose units
Taste	Neutral, flavorless	Sweet
Digestion	Slower, requires enzymatic breakdown	Very rapid absorption
Solubility in Water	Insoluble in cold water, forms a paste when heated	Soluble in water
Primary Function	Energy storage in plants, culinary thickener	Quick energy source

Conclusion

In conclusion, cornstarch is not a simple sugar but a complex carbohydrate known as a polysaccharide, meaning "many sugars". It is made from long, linked chains of glucose molecules which are too large to register as sweet on the human tongue. Instead, this structural complexity gives cornstarch its remarkable functional properties, such as its ability to thicken sauces and crisp up fried foods. While the body can break cornstarch down into glucose for energy, this process is much slower than with simple sugars, making it an entirely different type of carbohydrate both chemically and functionally.

Frequently Asked Questions

Cornstarch is a starch, which is a type of complex carbohydrate. While it is made of glucose, which is a simple sugar, its molecules are arranged in long, complex chains, fundamentally differentiating it from simple sugars.

Cornstarch is not sweet because its large polysaccharide molecules are too big to fit into the sweet taste receptors on your taste buds. Only after the starch is broken down into smaller glucose molecules through digestion does the sweetness become apparent.

No, cornstarch does not contain simple sugar. It is made of carbohydrates in the form of complex polysaccharides. While it will eventually be broken down into glucose (a simple sugar) during digestion, its uncooked form does not contain sugar.

Because cornstarch is a complex carbohydrate, it is digested more slowly than table sugar. This means it releases glucose into the bloodstream over a longer period, resulting in a more gradual, less dramatic rise in blood sugar.

The primary culinary use of cornstarch is as a thickening agent. When heated in a liquid, its starch granules swell and break, releasing molecules that form a viscous gel that thickens the mixture.

Cornstarch is made from the endosperm of the corn kernel. Through a wet milling process, the kernel's starchy part is separated, washed, and dried into a fine powder.

Yes, cornstarch is a complex carbohydrate. This classification refers to its molecular structure, which consists of long chains of simple glucose units, distinguishing it from simple carbohydrates like table sugar.