Investigation of the use of mung bean flour in gluten-free ready to drink tarhana soup production

A new, at a high nutritional value, ready to drink instant and a gluten-free tarhana like soup was produced for the first time in this study for celiacs by replacing rice flour with 50% mung bean flour and following by drum drying after fermentation. In produced gluten-free soup powders; physical properties (water and oil absorption capacities, water absorption index and water solubility index, foam capacity and stability, micro structure screening by SEM, birefringence) and chemical properties (moisture, ash, crude protein content, soluble protein content, gelatinization degree, total dietary fiber and gluten contents, total phenolic content, DPPH and FRAP antioxidant activities) were investigated. Color, flow behavior determination and sensory analyzes were carried out in soups prepared by dried powders. The effect of independent variables; feeding moisture (45-65%), drum speed (1-3 round) and pressure (75-95 psi) on quality and functional properties were analyzed using the response surface method. Optimum processing conditions were determined for the selected 4 responses (water absorption and water solubility index, gelatinization degree, overall acceptibility) in drum drying by utilizing method's desirability factor. Obtained soup powders can be a good dietary alternative for celiacs with the average of 21.90% protein and 3.44% total dietary fiber contents. The analyzed system parameters and product properties were mostly influenced by primarly the feed moisture, then the drum speed and at a lesser extent the pressure variable. Drum drying can provide a wide range of morphological and textural properties to modified starches. In this study, it was seen that all of the soups obtained by using drum dryer had a non-Newtonian pseudo-plastic flow behaviour characteristics. The pregelatinized soup powders produced had high water solubility (17.93-23.14%) and water absorption indexes (3.20-4.20 gjel /g) which were required for an instant property. A sufficient gelatinization has been achieved due to the average gelatinization degree of 90.49%. This was supported by; SEM micrograph images in which the granular structure was dispersed, polarized light microscopy analyzes where the birefringence was lost and the DSC thermograms where no endothermic peak was observed. In general, as the feed moisture increased and the process conditions hardened the total phenolic content of the powders (2.57-3.64 mg GAE / g) and antioxidant activities (DPPH; 6.28-9.96 µmolTE/g and FRAP; 26.02-42.88 µmolFe (II)/g) of soup powders increased. The sensorial data show that the overall acceptability values of the soups are related to the other sensory criteria examined and mostly affected by the consistency (r = 0.95). The results of the sensory analysis (according to the hedonic scale of 1-7 points) revealed that the use of mung bean&rice flour and drum dry cooking process yielded acceptable soup characteristics in most of the sensory properties examined with the average points of 4.98 ± 0.63. It may be concluded that; the obtained product of instant gluten-free mung bean soup which has higher nutrient value, can help to reduce nutritional deficiency and can be used practically in daily and social life by celiacs.