Methylpentoses are six-carbon sugars that carry only five hydroxyl groups, with rhamnose and fucose as the classic examples. They occur as components of plant gums, pectins, bacterial cell walls, seaweed polysaccharides, and some glycoproteins, where they influence texture, water binding, and microbial interactions. In food analysis they serve as useful markers: rhamnose levels help characterize pectin and gum arabic quality, and fucose appears in human milk oligosaccharides and fucoidans studied for prebiotic and health potential. Their distinctive structures make them identifiable by chromatography and mass spectrometry, supporting authenticity testing of gums and hydrocolloids.