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Inulin is a raw material that is most often extracted from chicory roots for industrial production. Inulin is a complex sugar belonging to the fructans. After starch, it is the second most common spare carbohydrate in the world of flora. It is found in more than 30,000 plants. Other examples of plants that contain high amounts of inulin are: Jerusalem artichoke, garlic, asparagus, salsify and dandelion root. In contrast, the most commonly consumed inulin-rich vegetables and fruits on a daily basis are onions, leeks, garlic, bananas, wheat, rye and barley. Inulin can also be produced by certain bacteria and fungi.
The history of inulin dates back to the early 19th century. In 1804, Valentin Rose, a German pharmacologist credited with the discovery of baking soda, among other things, detected a peculiar substance in the roots of the oman (Latin: Inula helenium). In 1817, British scientist Thomas Thomson named this compound “inulin” after the Latin name of this plant. German plant physiologist Julius Sachs pioneered the study of fructans. In 1864, he detected spherocrystals of inulin under a microscope after precipitation with ethanol.
Prebiotics are food components that are resistant to digestive enzymes in the digestive tract. These substances positively affect the host by selectively stimulating the growth of beneficial bacteria in the colon. They differ from probiotics in that they do not contain any microorganisms, but only stimulants.
Inulin contains in its chemical structure fructose residues linked by β-(2-1)-d-frutosyl bonds. The human body does not produce enzymes that can cut such bonds, so inulin is resistant to digestion in the small intestine. Almost 90% of inulin passes into the colon and is metabolized by bacteria present there, which produce short-chain fatty acids. A systematic review by Le Bastard et al. analyzed nine randomized, double-blind clinical trials, and in all of them, inulin consumption was associated with a significant increase in the number of Bifidobacterium bacteria. Other concordant results included increases in Anaerostipes, Faecalibacterium and Lactobacillus and a decrease in Bacteroides.
In people with constipation, inulin intake was associated with a significant increase in stool frequency. This confirms the potential effect of inulin on the composition of the human intestinal microflora. A meta-analysis by Yurrit et al. showed that inulin supplementation of 20-40g/day significantly improved the consistency, hardness and transit time of stools in people suffering from chronic constipation. In turn, consumption of each 1g of inulin increased wet stool by an average of 1.5-2g.
Inulin has found many uses in the food industry. The FDA, the U.S. Food and Drug Administration, has recognized it as safe and given it GRAS (Generally Recognized As Safe) status. It is used in the bakery, meat, dairy, and confectionery industries in many products:
- Cereal products i.e. breads, pastries, breakfast cereals;
- Dairy products, i.e. cheeses, processed cheese, fermented milk drinks, pastes, ice cream, frozen desserts;
- Products with reduced fat or sugar content.
Due to its high fibre content and prebiotic effect, it is used in functional foods. Functional foods resemble conventional foods in form, but in addition to providing nutrients they benefit health.
The wide use of inulin is based on its technological and functional properties. It improves the texture of the product, as well as has a stabilizing effect. It also works well as a fat and sugar mimetic. The highly branched polymers of inulin are characterized by good solubility. They are capable of forming gel-like particles, thus changing the texture of the product thereby providing a fat-like mouthfeel. Short-chain molecules, on the other hand, improve taste, sweetness and are used as replacements for sucrose. Hence the widespread use of chicory inulin in “light” products, i.e. those with reduced sugar or fat content.
Inulin is a natural carbohydrate with a number of health-promoting and functional properties. It is a source of dietary fibre. As a prebiotic, it stimulates the development of normal intestinal microflora and helps with constipation. When added to food products, it can improve texture, and can partially replace fat and sugar.