Development of a synbiotic dairy beverage incorporating Sri Lankan plant derived Inulin-type fructans

© 2015 Dr. Deshani Chirajeevi MudannayakeInulin-type fructans are linear polydisperse fructose polymers consisting mainly of β-(2-1) fructosyl-fructose linkages, studied and scientifically proven to have prebiotic properties. The present study aimed at identifying inulin sources grown in Sri Lanka, and to investigate their potential use as prebiotics. The overall study was conducted in five major experiments. The objective of the first experiment was to determine inulin-type fructan content in 20 selected food plants grown in Sri Lanka. Inulin content of selected plant parts were analyzed by thin layer chromatography and enzymatic spectrophotometry. Seven important inulin bearing plants, were identified. Those plants in descending order of inulin content were, Allium sativum (18%), Asparagus falcatus (17%), Asparagus racemosus (11%), Allium cepa (8%), Allium ampeloprasum (6%), Taraxacum javanicum (5%) and Vernonia ceneira (4% w/w fresh wt). The A. falcatus (AF) and T. javanicum (TJ) plants were chosen as inulin sources for further study. The second experiment was aimed to extract and purify inulin from roots of AF and TJ plants and, to compare chemical and physicochemical properties with commercial Chicory inulin (Chi I). Inulin contents in purified powders were analyzed by enzymatic spectrophotometry and HPLC techniques. Total phenolics, flavonoids and antioxidant capacities were determined by Folin–Ciocalteu, standard quercetin, and ABTS methods. Mineral composition was determined by atomic absorption spectrophotometry and flame photometry. FT-IR analysis was conducted for chemical characterization of inulins. The AF and TJ inulin powders contained 65% and 45% inulin content compared with Chi I, which contained 72% inulin (w/w, dry wt). FT-IR results confirmed similar molecular composition of AF, TJ and Chi inulin. AF and TJ inulin showed significantly (P<0.05) high phenolics, flavonoids and antioxidant capacity compared with Chi I. The third study investigated the effect of AF and TJ inulin on growth of two probiotic strains (B. animalis Bb-12 and L. acidophilus La-5) in skim milk. Selective enumeration of Bb-12 & La-5, measurement of pH & optical density (OD) were done to determine probiotic growth in skim milk. New inulins enhanced Bb-12 growth, while did not influence the growth of La-5 in skim milk. The OD and pH data showed clear negative correlation. The AF and TJ inulin concentrations 1, 2 and 3% were selected for further studies. The fourth experiment was aimed at evaluation of in vitro prebiotic properties of AF and TJ inulin in comparison with Chi I. Anaerobic, batch culture fermenters, inoculated with human fecal slurries were used as the in vitro gut simulants. Changes in growth of bifidobacteria, lactobacilli, clostridia, coliforms, total aerobes and anaerobes during 48 hrs of in vitro fermentation were determined using appropriate selective media. Short chain fatty acids (SCFA) (acetate, butyrate, propionate), lactate and inulin utilization were measured using HPLC. New inulins showed very similar in vitro prebiotic properties by increasing lactobacillus and bifidobacteria while reducing coliform and clostridium populations. In vitro SCFA production patterns were similar in the presence of all inulin types, except butyrate which was higher in the presence of TJ inulin. Up to 68% of added inulins were utilized by fecal microflora during in vitro fermentation. The objective of the final experiment was to develop synbiotic yoghurt beverage fortifying AF and TJ inulin and, investigate the effect of new inulin on probiotic viability, activity, sensory and physicochemical properties of yoghurt beverage. Plain and sweetened synbiotic yoghurt beverages were prepared with AF or TJ inulin with Bb-12 and La-5 probiotic strains. Acid production (acetate, butyrate, propionate and lactate), microbial growth, physical properties (pH, viscosity and color) during 21 days of refrigerated storage of beverages were investigated. Sensory properties of beverages were evaluated using 30 panelists, and 9 point hedonic scale. Addition of AF and TJ inulin increased the survival of Bb-12 and La-5 significantly (P