NEW FATTY ACID ESTERS OF SOLUBLE DIETARY FIBERS WITH EMULSIFYING PROPERTIES NADEZHDA PETKOVA1*, MINA TODOROVA1, KREMENA NIKOVSKA2, PANTELEY DENEV1** 1
University of Food Technologies, Department of Organic Chemistry and Microbiology, 26 Maritza Blvd., Plovdiv, Bulgaria, 2 University of Food Technologies, Departament of Catering and Tourism, 26 Maritza Blvd., Plovdiv, Bulgaria, E-mail address: *
[email protected], **
[email protected] Abstract Fatty esters of carbohydrates constitute an interesting group of non-ionic surfactants. These compounds are environmentally friendly, with low toxicity and present interest in agriculture, pharmaceutical, cosmetic and food industry. Inulin and fructooligosaccharides esters were synthesized by reacting these carbohydrates with methyl esters of saturated fatty acids (C12 to С18). The esterification reaction was performed in presence of catalyst NaOMe and absence of solvent. A new method for synthesis with the ultrasonic influence has been developed and applied. The fructooligosaccharides esters and modified inulin have been characterized by measurement of melting point, water activity, thin-layer chromatography (TLC) and FT-IR. A preliminary study of their emulsifying and stabilizing properties was analyzed. The rheological properties, dispersion and emulsion stability of oil-in-water emulsions (O/W) prepared with different concentration of inulin esters as emulsifier were investigated. Key words: inulin, fructooligosaccharides, ultrasonic synthesis, inulin fatty acid esters, fatty acid methyl esters (FAME), emulsifiers Introduction Fatty esters of carbohydrates constitute an interesting group of non-ionic surfactants [8,11]. These compounds present a good biodegradability and a low toxicity, which confer to them a particular interest in pharmaceutical [22], cosmetic [19], food industry and agriculture [11]. Polymeric surfactants attract considerable attention as dispersants for solid in liquid medium and as emulsifiers. In recent years, the interest to surfactants that are based on polysaccharides via the grafting of alkyl chains increased dramatically [8]. Inulin is a polydisperse linear polysaccharide, member of fructan family, which serves as a reserve carbohydrate in underground part of the Compositae plants such as Cichorium intybus, Inula helenium and Helianthus tuberosus [18, 20]. Inulin has been defined as consisting mainly of β-(2→1) fructosyl fructose units (Fm), and usually but not always the chain contains a terminal αglucopyranose unit (1→2) (GFn) at the reducing end (Figure 1). A small percentage of inulin molecules have a terminal fructoside unit found primarily in the pyranose form in aqueous solution [5]. The degree of polymerization (DP) of inulin varies from 2 to 70 and depends on plant species, harvesting time and post-harvest conditions [4]. Molecules with DP
