Maltose

What Is Maltose?

Maltose, commonly called malt sugar, is a disaccharide formed by two glucose molecules linked by an alpha-1,4-glycosidic bond. It is produced during the enzymatic breakdown of starch, a process that occurs when grains germinate and when starchy foods are digested. The enzyme amylase, present in both saliva and the pancreas, cleaves starch chains to produce maltose as an intermediate product.

Maltose has a sweetness approximately 30–60% that of sucrose and a glycemic index of around 105, making it one of the higher-GI sugars due to its rapid conversion to two glucose molecules upon digestion.

Maltose in Food Production

Maltose is central to the fermentation and brewing industries. During malting — the process of germinating and drying grains — starch is converted to maltose by naturally occurring amylase enzymes. This maltose then serves as the primary fermentable substrate for yeast in beer and whisky production.

Common food sources of maltose include:

• Malted grains: barley malt, malted wheat
• Fermented foods: beer, malt vinegar, certain breads
• Starchy foods during digestion: bread, cereals, potatoes
• Sweeteners: malt syrup, some rice syrups

Digestion and Health Considerations

Maltose is digested in the small intestine by the enzyme maltase (also called alpha-glucosidase), which splits it into two glucose molecules for rapid absorption. Because it yields two glucose units, maltose produces a significant insulin response and has a high glycemic effect.

People with glucose-galactose malabsorption or certain enzyme deficiencies may have difficulty digesting maltose. For individuals managing blood glucose levels — such as those with diabetes — foods high in malt sugar or malt-derived syrups should be consumed with awareness of their high glycemic impact. Maltose itself does not occur in appreciable quantities in most whole foods; it appears primarily as a product of starch digestion or food processing.