Ultrasound assisted low-temperature drying of kiwifruit. Effects on drying kinetics, bioactive compounds and antioxidant activity.
J Sci Food Agric. 2018 Nov 24. Epub 2018 Nov 24. PMID: 30471127
BACKGROUND: Low-temperature drying is considered to be a promising technique for food processing which preserves thermolabile compounds and might be intensified by acoustic assistance. The effect of acoustic assistance (20.5 kW/m) during low-temperature drying of kiwifruit (at 5, 10 and 15°C, and 1 m/s) on drying kinetics, bioactive compounds (such as ascorbic acid, vitamin E and total polyphenols) and antioxidant activity, was studied.
RESULTS: Drying time was shortened by a 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).
CONCLUSION: Overall, low-temperature drying of kiwifruit was enhanced by acoustic assistance preserving bioactive compounds and antioxidant activity, especially at 15°C. This article is protected by copyright. All rights reserved.