Influence of ultrasound pre-treatment and temperature on the quality and thermodynamic properties in the drying process of nectarine slices in a hot air dryer

Drying is one of the ways to reduce postharvest waste and processing in agricultural products. Drying with hot air is one of the most popular drying methods in the food industry. The purpose of this study is to investigate the effect of ultrasound and temperature on the quality and thermodynamic properties in the process of drying nectarine slices in a hot air dryer. The drying process was performed at four levels of ultrasonic pre-treatment of 0 min (control sample), 10, 20, and 40 min and three temperature levels of 50, 60, and 75 degrees C. Experiments were performed on 5 mm thick nectarine slices with 12 treatments and three replications. The obtained data were analyzed by a factorial test based on a completely randomized design. The moisture ratio change of nectarine samples was fitted with 12 thin-layer drying models. The results showed that by increasing the temperature and duration of the ultrasound treatment, drying time for nectarine slices decreased. The Page model was recognized as the best model for describing the drying behavior of nectarine slices through ultrasound. The highest amounts of shrinkage and color change were obtained as 31.35% and 25.03%, respectively, at the temperature of 75 degrees C and for the control samples. The use of ultrasound in the process of drying nectarine slices at different temperatures resulted in an increase in the effective moisture diffusion coefficient from 6.50 x 10(-10)to 2.11 x 10(-9) m(2)/s. The amount of specific energy consumption (SEC) in the process of drying nectarine slices was calculated to be 59.70 to 212.97 kwh/kg. Practical applications Postharvest drying of fruits is essential to increase shelf life and control waste. A certain level of a product's moisture can be reduced through extraction of water from it under controlled conditions in order to prevent the microbial growth that causes it to spoil. Moreover, the preservation of qualitative properties (such as color and shrinkage) and thermodynamic properties (such as reduced energy consumption) has attracted the attention of many researchers working on the drying process of agricultural products. In this study, the effect of ultrasound pre-treatment and temperature on the quality and thermodynamic properties in the drying process of nectarine slices in a hot air dryer were investigated. The results of this study can be useful in optimizing drying operations and improving the qualitative and thermodynamic properties. The results can also be applied as a technical basis for drying nectarine and designing the required equipment.