Carbohydrates, like proteins and fats, are major food constituents. They are divided into three main groups: monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides are simple sugars that cannot be hydrolyzed into simpler compounds. Oligosaccharides yield two to ten simple sugars on hydrolysis. The reducing ability of a sugar depends on the presence of a potentially free carbonyl group in its structure. Reducing sugars participate in Maillard browning. Polysaccharides yield a large number of sugars upon hydrolysis. Starches, with their ability to bind large amounts of water, are useful polysaccharide thickening agents. Commercial starches are obtained from cereal grains, root sources, or trees. Each starch has its own characteristics.