| Abstract [eng] |
Because the growing demand for higher nutritional value food, the technologies for isolation of valuable components from fruit, vegetable and grain processing by-products that could be used as functional components for food production are of great interest in scientific world. The aim of the work was to apply ultrasonic treatment in the case to increase the efficiency of soluble and insoluble dietary fiber (SK) extraction from by-products of rice processing industry and to evaluate their physicochemical and functional properties. The secondary food raw material formed during rice milling ‒ rice bran (RS), which are not rationally used despite the valuable components they contain was chosen for the experiment. Dry fractionation of raw material was applied in order to obtain RS fraction with higher SK content. In the first stage of the work, ultrasound (UG) was used for RS treatment to evaluate the efficiency of SK extraction with hot water. Using a composite experimental design, the temperature and time of UG treatment were optimized and the material-to-water ratio was selected to obtain the highest water-soluble (TSK) and insoluble fiber (NSK) yields. Based on the obtained experimental data, a reliable mathematical model for predicting TSK and NSK yields (R2 = 0,856 and R2 = 0,847, respectively) was developed and optimal ultrasonic treatment conditions (50 ℃, 30 min, raw material / water ratio 1:4) were determined. By treatment with ultrasound RS and extraction with hot water under these conditions, 6,68 g / 100 g s.m. TSK and 22,69 g / 100 g s.m. NSK. In the second stage of the work, different extraction methods (extraction with hot water and alkali; extraction by cellulase hydrolysis and ultrasonic extraction) were used to extract TSK, NSK and ŠSK. Ultrasonic extraction was found to be the most efficient method for recovering TSK, NSK and ŠSK (20,61; 72,59; 22,46 %, respectively). Microstructure analysis of TSK and ŠSK samples extracted in different ways showed that the extraction conditions affect the size of SK particles and their surface area, the homogeneity of the fiber structure. Qualitative analysis of SK saccharides and FT-IR analysis showed that residues of pyranose form (hexoses) predominate in TSK samples, while residues of furanose form (pentoses and hexoses) predominate in ŠSK samples. The results showed that the extraction conditions have a significant effect on the technological and bioactive properties of TSK and ŠSK. |
