- Fructans are a diverse group of polysaccharides composed primarily of fructose units, usually with a terminal glucose residue. They belong to the broader family of carbohydrates and are distinguished by the type of glycosidic linkages between the fructose monomers.
- The most common forms are inulin-type fructans, which have β-(2→1) linkages, and levan-type fructans, which are characterized by β-(2→6) linkages. In some cases, mixed-linkage fructans contain both types of bonds. These structural variations strongly influence their solubility, fermentability, and biological properties, making fructans an important class of natural carbohydrates.
- In the plant kingdom, fructans serve primarily as reserve carbohydrates. Unlike starch, which is the main storage carbohydrate in most plants, fructans accumulate in over 15% of flowering plant species, particularly in grasses (Poaceae), lilies, and members of the daisy family (Asteraceae). Plants store fructans in roots, tubers, bulbs, and stems, where they function not only as energy reserves but also as molecules that enhance stress tolerance. Fructans help plants survive drought, cold, and salinity by stabilizing membranes, retaining water, and acting as osmoprotectants. This ecological role explains why fructan-rich plants often thrive in temperate and arid regions.
- For humans and other animals, fructans are classified as dietary fibers and prebiotics. Because the human digestive system lacks enzymes capable of breaking down β-(2→1) or β-(2→6) linkages, fructans pass undigested through the small intestine and reach the colon. There, they are selectively fermented by beneficial gut microbiota, especially Bifidobacterium and Lactobacillus. This process supports digestive health, enhances mineral absorption, and produces short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, which contribute to gut and systemic health. Fructan consumption has been linked to improved bowel function, immune modulation, and potential reductions in risks of metabolic and inflammatory diseases.
- In the food industry, fructans—particularly inulin and oligofructose—are widely used as functional ingredients. They serve as fat replacers, sugar substitutes, bulking agents, and texture enhancers in products such as yogurt, baked goods, and beverages. Their mild sweetness and ability to improve mouthfeel without raising blood glucose levels make them particularly valuable for diabetic-friendly and low-calorie formulations. Fructans also contribute to satiety, supporting weight management diets.
- Fructans hold promise in biotechnology and medicine as well. Their prebiotic effects are being explored in nutraceuticals and therapeutic foods designed for gut health. Modified fructans and their derivatives are under study for use in drug delivery systems, protective coatings for probiotics, and biodegradable biomaterials. Because of their biocompatibility and fermentability, fructans are also being investigated for their role in modulating inflammation and protecting against certain chronic diseases.
