The effect of different pretreatment combinations on the physicochemical properties of melon pulp dried with vacuum assisted infrared dryer

In this study, it was aimed to determine the effect of different pretreatments on drying time and product quality characteristics in melon chips produced with vacuum assisted infrared dryer. For this purpose, eight different pretreatments with different combinations of citric acid, ethanol, ultrasound, boiling and freezing were applied and the drying times, physical, chemical and sensory properties of the melon chips were determined. The combination of citric acid, ethanol, ultrasound and freezing processes as pretreatment had the shortest drying time (70-75 minutes). Even though the drying time in this pretreatment was short, the total processing time was the longest (1050-1055 minutes) due to the long freezing process. This fastest drying sample had the highest rehydration rate and the lowest shrinkage rate. The highest shrinkage rate was determined in the sample (94.3%) pretreated with citric acid and ethanol combination. In the study, the L values of dried samples were generally higher than the L value of fresh melon. The highest L value (74.21) was found in the sample pretreated with citric acid and ethanol combination. The highest fructose content (20.11 g/100g KM) and the highest glucose content (20.8711 g/100g KM) were found in samples immersed into the the citric acid, and this sample was among the samples with the high total sugar content. The highest HMF (117.98 mg/kg KM) was detected in the sample pretreated with the combination of citric acid and ultrasound. In addition the amount of HMF was high in all samples pretreated with ultrasound. The samples immersed in the citric acid had the highest total phenolic content (2563.34 mg GAE/kg KM) and DPPH (7.47 mmol Trolox eq./gKM) values. On the other hand, the highest ABTS (14.88 mmol Trolox eq./gKM) value was detected in the sample immersed in citric acid-ethanol combination. Among the melon chips evaluated by the panelists, the sample pretreated by citric acid and boiling combination was found as the most appreciated samples. As a result of the study, it was seen that delicious and healthy melon chips can be produced in a shorter time with vacuum assisted infrared dryer and different pretreatment combinations. Thus, it is thought that melon, which cannot be found every season and cannot be stored for a long time, can be turned into melon chips, which is a healty snack food, and the product diversity can be provided for the market. Keywords: Antioxidant activity, Chemical properties, Infrared drying, Melon chips, Physical properties, Pretreatments