The effects of different drying methods and pre-treatments on drying characteristics and some quality properties in drying carrot (Daucus carota L.) slices

Carrot, have an important place in human health due to the rich nutrients they contain. This product is a highly preferred product in the food industry due to its wide range of uses such as carrot juice, dried carrots, carrot powder and carrot chips. Drying is a widely used method for preserving agricultural products such as fruits and vegetables. The main purpose of drying is to reduce excess moisture that may cause deterioration in the content of agricultural products, slow down oxidative and enzymatic degradation, and contribute to increasing the storage period and shelf life of products. The aim of the study is to determine the most suitable drying conditions for fresh carrot slices. Drying trials were carried out in a convective dryer, vacuum oven, laboratory type convective dryer and in the sun. Before drying experiments, carrot slices were kept in 3% citric acid solution and boiling water for 15 minutes. Pretreated and non-pretreated (control) carrot slices were dried by applying air temperatures of 50, 60, 70, and 80 °C. The effects of drying methods and pretreatments on the drying time, color change, rehydration properties, and thin layer drying patterns of the products were determined. To determine the drying kinetics, Lewis, Wang-Sing, and Midilli-Küçük theoretical models were used and their suitability was examined. As a result of the study, it was determined that increasing the drying temperatures and applying pre-treatments significantly reduced the drying time. In addition, the applied pretreatment, drying methods and temperatures affected the color values and rehydration properties of the dried products. According to the research results, the fastest drying was observed in the samples that were preboiled at 80 ℃. As a result of the drying experiments, the final product closest to the color values of fresh carrots in terms of color parameters was determined in the samples that were pretreated with citric acid in a laboratory type convective dryer at 80 ℃. It has been determined that Midilli-Küçük and Wang-Sing models are more suitable drying models for carrots. The most suitable method in terms of rehydration capacity and rate of dried carrot slices was determined at 70 ℃ rehydration water temperature, in laboratory type convective dryer at 70 ℃ and in samples with preblanching treatment.