The effects of ultrasound on quality and nutritional aspects of dried sour cherries during shelf-life

• US application influenced diffusion during sour cherry osmotic treatment and drying.
• During shelf-life antioxidant potential decreased gradually.
• Samples treated with US had a lower antiradical capacity than those untreated.
• Osmotic dehydration and storage caused a drastic fall in anthocyanins.
• US may quicken the loss of antioxidant potential.

The aim of this study was to investigate whether ultrasound (US) assistance during the osmotic pretreatment of sour cherries has any influence on quality and changes in the levels of bioactive compounds present in dried product during storage using an accelerated shelf-life test. Sour cherries of ‘Nefris’ variety were pitted in a frozen state and subjected to osmotic dehydration in a water bath fitted with ultrasound transducers (25 kHz, 0.4 W/cm2) and a shaking plate (30 rpm) in sucrose solution (60 °Bx, fruit to syrup ratio 1:4, 40 °C) and then convectively dried (60 °C, 9 h, 2.5 m/s). The osmotic dehydration lasted 120 min with (60US) and without US (0US) treatment. The application of US resulted in the enhancement of mass transfer after osmotic dehydration (higher dry matter content and lower water activity in dried 60US sample in comparison to 0US). Storage caused the deterioration of anthocyanin content and after 8 weeks of storage significant differences between samples became visible. Samples treated with US application had a lower antiradical capacity than those untreated. It can be anticipated that ultrasound application had a negative influence on anthocyanin content and may speed up the loss of antioxidant potential.