What are the 5 examples of non reducing sugars?

November 26, 2025 •

3 min read

Carbohydrates constitute over 90% of a plant's dry weight; a significant portion of these are non-reducing sugars. Non-reducing sugars lack a free aldehyde or ketone group, preventing them from acting as reducing agents. This structural characteristic makes them less reactive during food processing compared to reducing sugars.

Quick Summary

This article highlights the characteristics of non-reducing sugars and provides five examples: sucrose, trehalose, raffinose, stachyose, and verbascose. It explains the chemical basis of their non-reducing nature and their importance in biological systems and food processing.

Key Points

Structural Difference: Non-reducing sugars lack a free aldehyde or ketone group because their anomeric carbons are linked in a glycosidic bond.
Sucrose (Table Sugar): Composed of glucose and fructose, it is the most common non-reducing sugar, with both anomeric carbons involved in the linkage.
Trehalose (Fungi Sugar): A disaccharide of two glucose units, it serves as a stabilizer and energy reserve in many organisms, including fungi and insects.
Raffinose (Legume Sugar): This trisaccharide (galactose, glucose, fructose) is found in legumes and is indigestible by humans, leading to fermentation in the gut.
Stachyose and Verbascose: These are larger RFOs found in legumes; stachyose is a tetrasaccharide, and verbascose is a pentasaccharide, both indigestible by humans.
Chemical Stability: Their resistance to oxidation makes non-reducing sugars valuable in food processing for preventing unwanted browning and degradation.

Understanding Non-Reducing Sugars

Non-reducing sugars are carbohydrates that do not have a free aldehyde or ketone group, also called a carbonyl group, in their cyclic structure. In these molecules, the anomeric carbons of the monosaccharide units connect via a glycosidic bond, leaving no reactive groups available for oxidation. This differentiates them from reducing sugars such as glucose and fructose, which have a free functional group that can reduce other compounds, like copper ions in the Benedict's test. The stability of non-reducing sugars is crucial in biological processes, where they are transport and storage molecules, and in food science, where they resist browning reactions.

The 5 Examples of Non-Reducing Sugars

1. Sucrose

Sucrose, the most common non-reducing sugar, is a disaccharide commonly known as table sugar.

Composition: It is formed from one molecule of glucose and one molecule of fructose.
Bonding: The glycosidic bond links the anomeric carbon of the glucose unit ($\alpha$-1) to the anomeric carbon of the fructose unit ($\beta$-2). Because both reactive anomeric carbons are involved in the bond, neither can participate in a reducing reaction.
Natural Sources: Sucrose is found in abundance in sugarcane and sugar beets.

2. Trehalose

Trehalose is a non-reducing disaccharide valued for its protective properties in nature.

Composition: This sugar comprises two glucose molecules linked by an $\alpha, \alpha$-1,1-glycosidic bond.
Function: It acts as a stress protectant and energy source in various organisms, including fungi, bacteria, and insects, helping them resist conditions like desiccation and freezing.
Uses: Its stabilizing properties have made it valuable in the food and cosmetic industries.

3. Raffinose

Raffinose is a trisaccharide from the raffinose family of oligosaccharides (RFOs).

Composition: It consists of galactose, glucose, and fructose units.
Sources: This sugar is found in many plants, especially legumes, cabbage, and asparagus.
Significance: Since humans lack the enzyme ($\alpha$-galactosidase) to digest it, raffinose is fermented by bacteria in the large intestine, which can lead to flatulence.

4. Stachyose

Also an RFO member, stachyose is a larger oligosaccharide found in many vegetables.

Composition: Stachyose is a tetrasaccharide composed of one fructose, one glucose, and two galactose units.
Digestibility: Similar to raffinose, stachyose is not digested in the human small intestine due to a lack of the necessary enzyme, and it is fermented by gut microbes.
Food Source: It is abundant in legumes such as soybeans, green beans, and peas.

5. Verbascose

Verbascose is a pentasaccharide, representing the next level of complexity in the raffinose family.

Composition: It is built from one glucose, one fructose, and three galactose units.
Occurrence: Like other RFOs, it is found in the seeds of various legumes and other plant parts, serving as a carbohydrate reserve.
Properties: As an RFO, it is also indigestible by humans and fermented by gut microbiota.

Comparison of Reducing and Non-Reducing Sugars


Feature	Reducing Sugars	Non-Reducing Sugars
Free Anomeric Carbon	Yes, at least one is available.	No, all anomeric carbons are involved in glycosidic bonds.
Functional Group	Possess a free aldehyde or ketone group.	Lack a free aldehyde or ketone group.
Test Reaction (e.g., Benedict's)	Positive (produces a color change from blue to red/orange).	Negative (no color change) until hydrolyzed.
Common Examples	Glucose, Fructose, Lactose, Maltose.	Sucrose, Trehalose, Raffinose, Stachyose, Verbascose.
Maillard Reaction	Directly participate in Maillard browning reactions.	Do not participate directly, but can be hydrolyzed to reducing sugars that can react.

Conclusion: The Stability and Function of Non-Reducing Sugars

Non-reducing sugars are key in chemistry and biology, mostly because of their structural stability. By having their anomeric carbons locked in glycosidic bonds, they avoid the reactive properties seen in reducing sugars. This makes them ideal for safe transport in plants, stress protection in microorganisms, and reliable use in the food industry where browning is undesirable. Understanding these five examples—sucrose, trehalose, raffinose, stachyose, and verbascose—shows how molecular structure dictates biochemical function and industrial application.

For additional information, consider consulting the Chemical Society.

Frequently Asked Questions

The key chemical feature of a non-reducing sugar is that the anomeric carbons of its component monosaccharides are joined in a glycosidic bond, leaving no free aldehyde or ketone group available for oxidation.

To test for a non-reducing sugar, perform a hydrolysis step using dilute acid to break the glycosidic bonds. This releases the individual monosaccharides, which are reducing sugars, allowing a subsequent Benedict's or Fehling's test to give a positive result.

Sucrose is a non-reducing sugar because the glycosidic bond forms between the anomeric carbon of the glucose unit and the anomeric carbon of the fructose unit. This locks both reactive centers, preventing the molecule from opening to expose a free carbonyl group.

Most polysaccharides, like starch and cellulose, are non-reducing because the proportion of reducing end groups is very small compared to the total number of sugar units in the large polymer. The reactivity is essentially negligible.

No, non-reducing sugars do not participate directly in the Maillard reaction, which requires a reducing sugar. However, if hydrolyzed, the resulting monosaccharides can then participate in the reaction.

Trehalose is biologically significant as a stress protectant and energy reserve in many organisms. It helps creatures like insects and fungi survive freezing and dehydration by forming a glassy, protective matrix around cellular components.

Raffinose and stachyose are associated with flatulence because humans lack the enzyme $\alpha$-galactosidase needed to break them down in the small intestine. They pass into the large intestine, where gut bacteria ferment them, producing gas.