According to the Encyclopedia Britannica, an oligosaccharide is a carbohydrate that contains between three and ten simple sugars linked together. Oligosaccharides occur naturally in small amounts in many plants. They may also be formed by breaking down more complex carbohydrates.
The chicory root, Jerusalem artichoke, onion, garlic, leek, legumes and other plant foods contain oligosaccharides. Most of these carbohydrates are sweet. Oligosaccharides have a distinctive taste that has led to their use as a partial substitute for sugars and fats in some foods. Due to their increasing use in the food industry, more and more oligosaccharides are being produced synthetically, as their occurrence naturally is rather limited.