Starch is a non-reducing sugar because its chemical formula is stable and does not oxidize. Starch and a few types of sugar compounds, such as sucrose, are considered non-reducing sugars, explains Reference.com.
Amylose starch, commonly just called starch, is a non-reducing sugar because it does not oxidize easily, which means the oxygen molecule does not chemically combine with copper to turn into an acid. This, in turn, helps it store energy. According to Agriculture and Consumer Protection, starch comes in both crystalline form, amylose, and non-crystalline form, amylopectin. Starch granules vary in shape, ranging from round and lenticular, or lentil-shaped as commonly found in barley and wheat, to polyhedral, oval and reniform or kidney-shaped, found in oats, potatoes and peas.
Starch is one of the most critical carbohydrates because it is digestible and is found largely in roots, including potatoes, and seeds, such as wheat, rice and barley. Fructose and sucrose are also non-reducing sugars and are found in honey, fruits and vegetables.
Reducing sugars, on the other hand, are sugars that oxidize and a conversion takes place. These sugars include glucose, lactose, maltose and galactose. These sugar molecules are found commonly in honey, fruit, corn syrups, milk, dairy products, fermented dairy products and malt.