The effect of different drying techniques on some quality properties of wheat germ

In this study, the stabilization of wheat germ was carried out by combining convectional (in oven), vacuum and microwave drying methods, as well as a combination of oven and microwave and vacuum dryer and microwave. Oven drying processes were carried out at 80, 90 and 100°C. The samples were dried at 80, 90 and 100°C under absolute pressure of 20 and 60 kPa by vacuum drying method. Microwave drying processes were carried out at 100, 150 and 200 W microwave power. Drying process by combining oven and microwave at 80, 90 and 100°C and 200 W microwave power; Drying process by combining vacuum dryer and microwave was carried out at 80, 90, 100°C and 20, 60 kPa absolute pressure and 200 W microwave power. The drying characteristics of the samples were determined. Page and Modified Page, which are semi-theoretical drying models of the oven drying process; It has been determined that Henderson and Pabis models for drying in vacuum dryer under 20 kPa absolute pressure, Page and Modified Page models for 80 oC under 60 kPa absolute pressure, Logarithmic for 90 oC and Lewis models for 100 oC are the models that best describe the experimental humidity change. Various analyzes were carried out to determine the changes in some quality parameters and nutrient contents of the samples dried in the oven during the drying process (color, water activity values, total antioxidant activity, total phenolic substance, % oil content, peroxide number and lutein content). It was determined that the changes in total antioxidant activity, total phenolic substance and lutein amount, which are quality factors examined in drying with oven, conform to the second-order kinetic model. The water activity decreased the most in the samples dried by combining vacuum dryer and microwave. The highest loss in antioxidant activity is in the samples dried by microwave drying, and the least loss in the samples dried in combination in an oven-microwave combination at 100°C+200 W; It was determined that the highest loss in total phenolic substance was in the samples dried at 80°C 60 kPa+200 W vacuum dryer-microwave combination, and the least loss was in the samples dried at 100°C under 60 kPa absolute pressure in the vacuum dryer. The percentage of oil is highest in the samples dried under 60 kPa pressure in a vacuum dryer at 80°C and the minimum combination is in the samples dried in an oven-microwave combination at 100°C+200 W. and in the samples dried in vacuum dryer at 100°C under maximum 60 kPa absolute pressure. The amount of lutein was determined the least in the samples dried in an oven at 80°C and the maximum in the samples dried in the microwave at 100 W. At the end of the study, it is the vacuum dryer-microwave drying processes that have the least amount of loss in bioactive components. In addition, when the study was evaluated in terms of peroxide number, it was determined that the minimum peroxide number value was obtained in the drying processes in the oven. In this respect, it was concluded that the oven drying method is more suitable than other methods.