Effect of continuous and intermittent ultrasound on drying time and effective diffusivity during convective drying of apple and red bell pepper |
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Authors: | Katharina Schössler Henry JägerDietrich Knorr |
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Affiliation: | Department of Food Biotechnology and Food Process Engineering, Technische Universität Berlin, Königin-Luise-Str. 22, 14195 Berlin, Germany |
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Abstract: | A new approach of ultrasound-assisted convective drying was tested in this study using a screen as product support and sound transmitting surface. Red bell pepper and apple cubes were dried at 70 °C in a laboratory scale hot-air drying oven. In addition to continuous ultrasound used for both products, intermittent ultrasound was applied for apple drying reducing net sonication time to 50% and 10%. Significant improvements of drying characteristics were observed for continuous sonication and intermittent ultrasound at 50% net sonication time. Experimental data were fitted with eight models, among which the Midilli model resulted in the best fit with R2 > 0.9988 and reduced χ2 ? 0.0002. The influence of ultrasound on drying time to reach 20% and 30% residual moisture content as well as on effective moisture diffusivities and drying periods is discussed. |
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Keywords: | Convective drying Continuous and intermittent ultrasound Screen Red bell pepper Apple |
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