Innovative drying applications in drying tarhana: Impact on product properties

Tarhana is a healthy and traditional product known and widely consumed, especially in our country. Produced in many regions, especially in the Aegean Region, tarhana contains yogurt, flour and vegetable purees and/or tomato paste as the basic ingredients. This dough, prepared with various ingredients, is dried and ground after fermentation to produce a nutritious product with a long shelf life. Powdered tarhana products, which are popular in every region of Turkey, are also produced industrially and hot airdrying systems are used for drying in the facilities. In these drying processes, which are carried out in a long time with high energy input and require intensive grinding process afterwards, the nutritional content of the product decreases and the quality of the product is negatively affected. In this study, refractance window drying, infrared assisted refractance window drying, hot air drying and traditional drying methods were used for drying tarhana dough and various physicochemical and microbiological properties of the powder products were comparatively determined. For this purpose, infrared assisted refractance window drying process conditions were first optimized by response surface method. The independent variables of the experimental design were laying thickness (1-3 mm), product surface temperature (32-40 °C) and circulation water temperature (60-90 °C). Minimum drying time, maximum amount of total water soluble vitamins (ascorbic acid and vitamins B3, B6, B9) and minimum browning index were selected as dependent variables. As a result of the optimization studies carried out under these conditions, 1.5 mm laying thickness, 36 °C surface temperature and 85 °C circulation water temperature were determined as optimum conditions. In order to evaluate the effectiveness of infrared (IR) support in the KPK drying method, additional drying trials were conducted without the use of infrared lamps, using the optimal conditions (spreading thickness and circulation water temperature) previously established for the KDKPK method. For the SHK method, drying parameters were determined based on data reported in the literature for tarhana drying, and were set as follows: 3 mm spreading thickness, 1.86 m/s air velocity, and 80 °C drying temperature. To represent traditional production, tarhana dough was spread in small portions onto a clean white cotton cloth and allowed to dry under ambient conditions. The tarhana samples obtained from all drying methods were analyzed comparatively in terms of their characteristic physicochemical and microbiological properties over a 90-day storage period, evaluated at five distinct time points. The drying time of tarhana dough was calculated as 43 minutes for infrared assisted refractance window drying system, 55 minutes for refractance window drying system, 220 minutes for hot air-drying method and approximately 96 hours for traditional drying method. Considering the drying times, it was determined that the infrared assisted diffraction window drying method significantly shortened the drying time. When the results obtained within the scope of the thesis were evaluated in general, it was determined that innovative drying applications (infrared assisted refractance window drying system - refractance window drying system) significantly reduced the drying time of tarhana and bioactive components were better preserved in these drying methods. It was determined that the powder flow properties and color properties of the products obtained by infrared assisted refractance window drying method were better than the tarhanas produced by other methods, and this method was superior in other physical analyzes. The highest protein content, free amino acid content, ascorbic acid and niacin content, total phenolic matter, antioxidant activity and carotenoid content were determined in tarhanas obtained by refractance assisted diffraction window drying method. Although more volatile components were detected in tarhanas obtained by traditional drying method, it was determined that the components were better preserved in innovative methods. It was also determined that the microbial activity of tarhanas produced in the traditional drying method was higher, while the infrared support in the innovative methods limited the microbial activity. As a result, it was evaluated that using these innovative methods for drying tarhana is a suitable alternative drying method in terms of product quality