Ultrasound assisted dehydration of kumquat fruit and determination of qality parameters

In this thesis, kumquat fruits (Fortunella margarita Swingle) were dried in different drying conditions by applying ultrasonic pretreatment (US). Drying time and quality characteristics of the kumquat fruits were examined. Fruits were dried at 70 °C temperature, 0,83 m/s air speed and 180W microwave power by applying US pretreatment. US pretreatment was applied before 70 °C drying process in ultrasonic bath for 10, 20, 30 min at 40 kHz frequency and 1:4 of fruit/water ratio. US pretreatment was applied before microwave drying process at 40 kHz frequency for 30 min and 1:4 of fruit/water ratio. US pretreatment was not applied to control group. Sample collection and weight measurement were performed during drying process periodically. Soluble solids (°Brix), total dry matter, ash, pH, titratable acidity, ascorbic acid, rehydration capacity, shrinkage, total color change with Hunter L, a, b values and browning index, chroma, hue angle parameters were determined at various dehydration stages and after. While constant and declining periods were observed during drying process at 70 °C, increasing, constant and declining periods were observed at microwave drying. Effective moisture coefficients of samples were determined between 4,5x10-10 and 7,3x10-10 m2/s. It was determined that 30 min US pretreatment provided decreasing of drying time by about 14 %-22 % for drying process at 70 °C and microwave drying, respectively. It was determined that Midilli-Küçük model was the best model explained the drying behavior. However, Newton and Page models were also offered for 70 °C drying process because of that have got less parameter. At the same time Page model was offered for microwave drying.Water activities after dehydration of fruits was detemined as 0,26-0,32-0,33-0,34- 0,38-0,44 for control, 10US, 20US, 30US grups at 70 °C and control MW, 30MW, respectively.Ascorbic acid content of samples decreased during drying. Least change in ascorbic acid was observed in 30US group for dried fruits at 70 °C dried and microwave dried fruits. Thermal degradation of ascorbic acid was fitted to first order reaction kinetic.Determination of Hunter L, a, b values were carried out for peel and slice of kumquat fruit. Change in L, a, b values showed differences between process groups. Browning index, hue angle and chroma value decreased during drying. Reaction kinetics of total colour change was fitted to zero order rection kinetics for control, 10US, 30US groups in 70 °C drying process. However, first order reaction kinetic was determined for 20US group in 70 °C drying process. In microwave drying, it was fitted to zero and first order for control group and zero order for 30US.It was determined that maximum shrinkage occurred in 30US group in both dried fruits at 70 °C and microwave drying. The samples which dried at 70 °C and microwave dried were fitted to diffrent models.Highest rehydration capacity was observed at 30US group in both samples that dried at 70 °C and microwave dried. Groups was fitted to different models.Sensory analysis was conducted as color, odor, flavor, appearance, chewiness, sweetness, acidity, dryness, bitterness (from the shell) parameters. The control and 10US groups at 70 °C and the control group at microwave received highest admiration from panelists.