Modern nutrition focuses on a relationship between food quality and health promotion. In recent years the food industry is experiencing the rise in demand for the value-added products. This trend will continue undoubtedly, and it is evident in both developed and developing countries [1]. Dietary fibres (DF) are one of the focuses of the health beneficial approach. By the most popular definition by European Food Safety Authority (EFSA), that is used in regulatory context, the dietary fibres are non-digestible carbohydrates (non-starch polysaccharides, resistant oligosaccharides and resistant starch) plus lignin [2].

Naturally occurring carbohydrate polymers involving non-starch polysaccharides (NSPs) represent a class of natural biomacromolecules that are widely derived from marine algae, plants, and edible mushrooms [3]. The term NSPs comprise all the plant polysaccharides except starch, and they have complex structure containing up to several hundred thousand monosaccharides units. The most abundant plant cell wall NSPs include hemicellulose, cellulose, and pectins; while fructans, and galactomannans, and glucomannans represent NSP group that is not so copious and serves as the storage polysaccharides within the plants [4,5].

Consumption of NSPs rich foods has approved beneficial effects that include immunomodulatory, anti-diabetic, anti-tumerogenic, antiviral, antioxidant, anti-inflammatory and anti-atherosclerogenic activities [5,6] exhibited by several biological activities that depend on NSPs extraction and purification, and their structural features [3].

In focus of this paper are fructans and their fractions, regarding their widespread application in food industry and dual effects on human health. Application of fructans in general will differ since long-chain fructans are characterized by lower solubility, higher sweetness, higher heat resistance, and higher viscosity than short-chain fructans. Fructans showed a high potential for application in the food industry as thickeners, sweeteners, as a fat and sucrose replacers and fillers (lowering energy value of foods), for improvement of the texture of food, which contribute to the food functionality. Fructans as well as all other NSPs are not connected by α-1-4Glc and α-1-6Glc glycoside linkage and they usually cannot be degraded by human endogenous enzymes (HEE). Absence of HEE dictates exertion of a variety of beneficial biological effects of fructans as part of DF in digestive tract function of healthy population. This is suggested based on the results by in vitro and in vivo studies which showed that fructans (both short- and long-chain) possess immunomodulatory properties and protect human intestinal barrier function thus preventing intestinal inflammation [7,8].

However, along with the health benefits, the consumption of food rich in fructan fractions, namely fructooligosaccharides (FOS) and fructose (in excess to glucose), can cause problems and disturbances in the gastrointestinal tract function (since they cannot be degraded by HEE). These compounds are osmotically active, pass through the small intestine and undergo fermentation by colonic bacteria producing gases such as methane and hydrogen that lead to bloating and worsening symptoms of irritable bowel syndrome (IBS). This condition affects 6.5 to 34.2 % of the world's population of all ages, and mostly the female population [9,10]. Research has shown that the population of western countries often encounters these health problems, which is conditioned by lifestyle and diet. In nutrition, bakery products as staple food, especially made from wholegrain flour are a particular problem, due to their high content of these specific dietary fibres [11,12].

Bearing in mind all above mentioned there is a knowledge gape in available plant sources of FOS degrading enzymes applicable as natural food additives for lowering FOS content during food production for growing population suffering from IBS. This review summarizes and provides consolidated data on the most important fructan rich plant sources, based on the fact that plants rich in fructan at the same time possess the enzymes responsible for their modification (which includes hydrolysis) [13,14]. The work also brings future perspectives for the safe use of fructans, especially in the bakery sector, since cereals are staple foods all around the world and therefore represent significant portion of human diet due to their nutritional value, including high DF content.