Effects of Physical and Chemical Pretreatments on Drying and Quality Properties of Blackberry ( Spp.) in Hot Air Dryer

This research examines the impact of various pretreatments on effective moisture diffusivity coefficient ( ), activation energy ( ), specific energy consumption (), color, and shrinkage of blackberry ( spp.). Hot air drying experiments were conducted under three different temperatures (50, 60, and 70°C) and four pretreatments, including thermal pretreatment by hot water blanching at 70, 80, and 90°C, pulse pretreatment with microwave having power of 90, 180, and 360 W, chemical pretreatment using ascorbic acid (1% in distilled water), and mechanical pretreatment using ultrasonic vibration with working frequency of 28 ± 5% kHz for 15, 30, and 45 min. The results show that the highest value, which was 1.00 × 10 m/s, could be achieved by using a microwave pretreatment with power and drying temperature of 360 W and 70°C͘, respectively. Moreover, the lowest value obtained from this similar pretreatment condition was 3.10 × 10 m/s at a drying temperature of 50°C, while ranged from 13.61 to 26.02 kJ/mol. The highest and lowest were 269.91 kW hr/kg for the control sample and 75.63 kW hr/kg for the microwave pretreatment, respectively. Furthermore, the largest color change and shrinkage were detected in ascorbic acid pretreatment and control sample, respectively.