Low‐temperature drying is considered to be a promising technique for food processing. It preserves thermolabile compounds and might be intensified by acoustic assistance. The effect of acoustic assistance (20.5 kW m−3) during low‐temperature drying of kiwifruit (at 5, 10 and 15 °C, and 1 m s−1) on drying kinetics, bioactive compounds (such as ascorbic acid, vitamin E, and total polyphenols), and antioxidant activity was studied.
Drying time was shortened by 55–65% when using power ultrasound. A diffusion model was used to evaluate the drying kinetics. The effective diffusion coefficient increased by 154 ± 30% and the external mass transfer coefficient increased by 158 ± 66% when ultrasound was applied during drying, compared with drying without ultrasound application. With regard to bioactive compounds and antioxidant activity, although samples dried at 15 °C presented significantly higher (P < 0.05) losses (39–54% and 57–69%, respectively) than samples dried at 5 °C (14–43% and 23–50%, respectively) when ultrasound was not applied, the application of ultrasound during drying at 15 °C significantly reduced (P < 0.05) those losses in all quality parameters (15–47% and 47–58%, respectively).
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.