Blackberry drying with various pretreatments of thermal, pulsed, chemical and mechanical using convective -infrared combined method

Document Type : Research Article


1 Moghan College of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran

2 Department of Biosystems Engineering, University of Mohaghegh Ardabili, Ardabil, Iran.

3 Department of Biosystem Engineering, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Iran


In this research was investigated the impact of various pre-treatments on effective moisture diffusivity coefficient (Deff), specific energy consumption (SEC), total color difference and shrinkage of blackberry (Rubus spp) in convective – infrared dryer. Experiments were done at three temperature leveles 50, 60, 70 °C with four different pretreatments, including of blanching thermal pretreatment at 70, 80, 90 °C, pulsed pretreatment with microwaves power 90, 180, 360 W, chemical with Ascorbic acid solution at concentration of 1% and mechanical pretreatment with ultrasound in times of 15, 30, 45 min. Results shown that the highest and lowest of Deff value (1.43×10-8 m²/s) and amount (55.52 kWh/kg) was obtained using microwave pretreatment under 360 W power and 70 oC drying temperature, respectively. Also, the minimum and maximum extent of Deff (4.24×10-9 m²/s) and (239.89 kWh/kg) were in controlled sample and drying temperature of 50 °C, respectively. The highest amount of color difference (30.28) and shrinkage (55.62%) were seen in controlled sample. The lowest value of color difference (7.01) and shrinkage (19.23%) was obtained in microwave pretreatment with power of 360 W and drying temperature of 70 oC. So, the value of SEC (76.86%), color difference (76.85%) and shrinkage (65.43%) of samples reduced significantly (P<0.05) using various pretreatments, respectively.

Graphical Abstract

Blackberry drying with various pretreatments of thermal, pulsed, chemical and mechanical using convective -infrared combined method


  • Blackberry drying using convective-infrared dryer and pretreatment of ultrasound, microwave, blanching and citric acid.
  • Calculation of specific energy consumption (SEC) and effective moisture diffusivity coefficient (Deff), and investigation of color and shrinkage of product during drying
  • The highest Deff value using microwave pretreatment and lowest extent of this parameter were obtained in controlled sample
  • Highest and lowest amount of SEC were obtained in controlled sample and microwave pretreatment, respectively
  • The highest amount of color changes and shrinkage were seen in controlled sample.


Main Subjects

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