Thermodynamic and Quality Performance Studies for Drying Kiwi in Hybrid Hot Air-Infrared Drying with Ultrasound Pretreatment

• Main Authors: Ebrahim Taghinezhad, Mohammad Kaveh, Antoni Szumny
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Applied Sciences
• Subjects: dry; efficiency; energy; kiwifruit; quality; ultrasound
• Online Access: https://www.mdpi.com/2076-3417/11/3/1297

The present study examined the effect of ultrasonic pretreatment at three time the levels of 10, 20 and 30 min on some thermodynamic (effective moisture diffusivity coefficient(<i>D_eff</i>), drying time, specific energy consumption (<i>SEC</i>), energy efficiency, drying efficiency, and thermal efficiency) and physical (color and shrinkage) properties of kiwifruit under hybrid hot air-infrared(<i>HAI</i>) dryer at different temperatures (50, 60 and 70 °C) and different thicknesses (4, 6 and 8 mm). A total of 11 mathematical models were applied to represent the moisture ratio (<i>MR)</i> during the drying of kiwifruit. The fitting of <i>MR</i> mathematical models to experimental data demonstrated that the logistic model can satisfactorily describe the <i>MR</i> curve of dried kiwifruit with a correlation coefficient (<i>R</i>²) of 0.9997, root mean square error (RMSE) of 0.0177 and chi-square (<i>χ</i>²) of 0.0007. The observed <i>D_eff</i> of dried samples ranged from 3.09 × 10⁻¹⁰ to 2.26 × 10⁻⁹ m²/s. The lowest <i>SEC</i>, color changes and shrinkage were obtained as 36.57 kWh/kg, 13.29 and 25.25%, respectively. The highest drying efficiency, energy efficiency, and thermal efficiency were determined as 11.09%, 7.69% and 10.58%, respectively. The results revealed that increasing the temperature and ultrasonic pretreatment time and decreasing the sample thickness led to a significant increase (<i>p</i> < 0.05) in drying efficiency, thermal efficiency, and energy efficiency, while drying time, <i>SEC</i> and shrinkage significantly decreased (<i>p</i> < 0.05).