Use of Novel Drying Technologies to Improve the Retention of Infused Olive Leaf Polyphenols

The infusion of phenolic extracts in dried fruits constitutes an interesting means of improving their nutritional content. However, drying can affect the further process of impregnation. In this work, different drying treatments (air temperature and ultrasound application) were applied to apple samples and impregnated with olive leaf extract. The application of ultrasound during drying did not significantly (p<0.05) affect the infusion capacity of samples, but the ultrasonically assisted dried samples showed a greater antioxidant capacity than those conventionally dried. The highest content of oleuropein and verbascoside was found in samples dried at low temperature using ultrasound.The authors acknowledge the financial support of the Spanish Ministerio de Economia y Competitividad (MINECO) and FEDER, and the Generalitat Valenciana (from the projects DPI2012-37466-CO3-03, PROMETEO/2010/062, and the FPI fellowship granted to J.V. Santacatalina).Santacatalina Bonet, JV.; Ahmad-Qasem Mateo, MH.; Barrajón-Catalán, E.; Micol, V.; García Pérez, JV.; Cárcel Carrión, JA. (2015). Use of Novel Drying Technologies to Improve the Retention of Infused Olive Leaf Polyphenols. Drying Technology. 33(9):1051-1060. https://doi.org/10.1080/07373937.2014.982251S1051106033

Atmospheric freeze drying assisted by power ultrasound

[EN] Atmospheric freeze drying (AFD) is considered an alternative to vacuum freeze drying to keep the quality of fresh product. AFD allows continuous drying reducing fix and operating costs, but presents, as main disadvantage, a long drying time required. The application of power ultrasound (US) can accelerate AFD process. The main objective of the present study was to evaluate the application of power ultrasound to improve atmospheric freeze drying of carrot. For that purpose, AFD experiments were carried out with carrot cubes (10 mm side) at constant air velocity (2 ms-1), temperature (-10ºC) and relative humidity (10%) with (20.5 kWm-3, USAFD) and without (AFD) ultrasonic application. A diffusion model was used in order to quantify the influence of US in drying kinetics. To evaluate the quality of dry products, rehydration capacity and textural properties were determined. The US application during AFD of carrot involved the increase of drying rate. The effective moisture diffusivity identified in USAFD was 73% higher than in AFD experiments. On the other hand, the rehydration capacity was higher in USAFD than in AFD and the hardness of dried samples did not show significant (p<0.05) differences. Therefore, US application during AFD significantly (p<0.05) sped-up the drying process preserving the quality properties of the dry product.Santacatalina Bonet, JV.; Carcel Carrión, JA.; Simal, S.; García Pérez, JV.; Mulet Pons, A. (2012). Atmospheric freeze drying assisted by power ultrasound. IOP Conference Series: Materials Science and Engineering. 42:5-8. doi:10.1088/1757-899X/42/1/012021S5842Stawczyk, J., Li, S., Witrowa-Rajchert, D., & Fabisiak, A. (2006). Kinetics of Atmospheric Freeze-drying of Apple. Transport in Porous Media, 66(1-2), 159-172. doi:10.1007/s11242-006-9012-4Wolff, E., & Gibert, H. (1990). ATMOSPHERIC FREEZE-DRYING PART 1 : DESIGN, EXPERIMENTAL INVESTIGATION AND ENERGY-SAVING ADVANTAGES. Drying Technology, 8(2), 385-404. doi:10.1080/07373939008959890García-Pérez, J. V., Cárcel, J. A., Benedito, J., & Mulet, A. (2007). Power Ultrasound Mass Transfer Enhancement in Food Drying. Food and Bioproducts Processing, 85(3), 247-254. doi:10.1205/fbp07010Gallego-Juárez, J. A., Riera, E., de la Fuente Blanco, S., Rodríguez-Corral, G., Acosta-Aparicio, V. M., & Blanco, A. (2007). Application of High-Power Ultrasound for Dehydration of Vegetables: Processes and Devices. Drying Technology, 25(11), 1893-1901. doi:10.1080/07373930701677371Hassini, L., Azzouz, S., Peczalski, R., & Belghith, A. (2007). Estimation of potato moisture diffusivity from convective drying kinetics with correction for shrinkage. Journal of Food Engineering, 79(1), 47-56. doi:10.1016/j.jfoodeng.2006.01.02