Pentosans are a class of polysaccharides found in plant cell walls, primarily composed of pentose sugars like xylose and arabinose. They form a major part of hemicellulose in cereals, bran, and wood. In food science, they influence dough rheology, water retention, and bread texture while serving as dietary fiber with benefits for gut health. Chemically, they consist of beta-1,4-linked xylopyranose backbones often substituted with arabinose. They are not a single molecular entity but polymers that can be water-soluble or insoluble depending on structure and extraction. Pentosans are hydrolyzed to pentoses under acidic conditions and play roles in both nutrition and industrial processes like papermaking.