Drying characteristics and quality attributes of apple slices dried by a non-thermal ultrasonic contact drying method

Ozan Kahraman, Amir Malvandi, Luis Vargas, Hao Feng

Research output: Contribution to journalArticlepeer-review


Drying is one of the most prevalent methods to reduce water activity and preserve foods. However, it is also the most energy-intensive food processing unit operation. Although a number of drying methods have been proposed and tested for the purpose of achieving a time- and energy-efficient drying process, almost all current drying methods still rely on thermal energy to remove moisture from the product. In this study, a novel use of power ultrasound was explored for drying of apple slices without the application of heat. The non-thermal ultrasound contact drying (US-CD) was performed in the presence of an air stream (26–40 °C) flowing over product surface to remove mist or vapor produced by the ultrasound treatment. The effects of the non-thermal US-CD, hot-air drying (HAD), and freeze drying (FD) on the changes in rehydration ratio, pH, titratable acidity, water activity, color, glass transition temperature, texture, antioxidant capacity, total phenols, and microstructures of the samples were evaluated. The moisture content of the apple slices reached below 5% (w.b.) after 75–80 min of US-CD, which was about 45% less than that of the HAD method. The antioxidant capacity and total phenol contents of the US-CD samples were significantly higher than that of the AD samples. The non-thermal ultrasonic contact drying is a promising method which has the potential to significantly reduce drying time and improve product quality.

Original languageEnglish (US)
Article number105510
JournalUltrasonics Sonochemistry
StatePublished - May 2021


  • Antioxidant capacity
  • Apple
  • Microstructure
  • Total phenols
  • Ultrasonic drying

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Environmental Chemistry
  • Radiology Nuclear Medicine and imaging
  • Acoustics and Ultrasonics
  • Organic Chemistry
  • Inorganic Chemistry


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