ISSN: 1314-6246 Gyurova & Enikova J. BioSci. Biotechnol. 2015, SE/ONLINE: 209-213 REVIEW SPECIAL EDITION / ONLINE Section “Biotechnologies & Applied Biology” Second National Youth Conference “Biological sciences for a better future”, Plovdiv, October 30-31, 2015 209 Desislava Gyurova 1 Rositsa Enikova 2 Dietary fibers – definitions, classifications and analytical methods for the physiological assessment of their content in foods Authors’ addresses: 1 Department ”Organic Analysis”, National Center of Public Health and Analyses, Sofia, Bulgaria. 2 Department “Microbiological Analyses”, National Center of Public Health and Analyses, Sofia, Bulgaria. Correspondence: Desislava Gyurova Department” Organic Analysis”, National Center of Public Health and Analyses, Sofia 1431, Bulgaria. e-mail: d.k.gyurova@gmail.com ABSTRACT The aim of this study is to present the most contemporary interpretation of the term “dietary fiber” as an ingredient of carbohydrates and its importance in human nutrition. The authors emphasize the “evolution” of the definition for dietary fibers in the years, as well as different approaches in the methods for their determination. The knowledge of the composition of foods rich of dietary fibers and oligosaccharides; and the harmonization of analytical methods together are a prerequisite for their correct identification and determination in the process of completion of the database for chemical composition of Bulgarian foods as well as in exchange of analytical data at regional and international level. Key words: dietary fiber, oligosaccharides, physiological properties, foods Introduction Dietary fibers are nowadays defined as “edible plant and animal material not hydrolyzed by the endogenous enzymes of the human digestive tract” (Commission Directive, 2008). They are assigned to the group of non-starch polysaccharides (including lignin) and Regulation EU № 1169/2011 (Regulation EC, 2011) on food labeling sets the following definition: “Dietary fibre means carbohydrate polymers with a degree of polymerisation (DP) not lower than 3 which are neither digested nor absorbed in the small intestine.” The fiber categories contained in foods are defined by the Regulation as: a). Edible carbohydrate polymers naturally occurring in the food as consumed, b). Carbohydrate polymers, which have been obtained from food raw material by physical, enzymatic or chemical means, that have beneficial physiological effect proven by generally acknowledged scientific evidence, c). Edible synthetic carbohydrate polymers, those have beneficial physiological effect proven by generally acknowledged scientific evidence.” Discussion The current European legislation has set a value for the energy conversion factors for dietary fibers of about 8 kJ/g (4 kcal), and the recommended daily intake for adult population as set in scientific publications is from 20 to 25 g. In the earlier periods of progress of the science concerning non-starch polysaccharides the fibers were identified as “soluble” and “insoluble”. Those terms were very valuable for the initial understanding of the physiological properties of dietary fibers, incorporating the simple division into fibers that principally affect the glucose and lipid absorption in the small intestine (the soluble ones) and fibers that slowly and incompletely ferment with a marked effect on gastrointestinal functions (the insoluble ones). This division, though, is not chemically well substantiated but depends more on extraction conditions (Asp, 1992). Besides, the physiological differences are not very essential in most of the soluble dietary fibers that ferment quickly and fully while not all insoluble fibers affect glucose and lipid absorption. From physiological point of view the dietary fibers pass undegraded from the human small intestine to the colon where a part of them could undergo fermentation under the effect of intestinal