title: Impact of applied ultrasonic power on the low temperature drying of apple.
abstract: Low temperature drying (LTD) allows high-quality dried products to be obtained, preserving the nutritional properties of fresh foods better than conventional drying, but it is a time-consuming operation. Power ultrasound (US) could be used to intensify LTD, but it should be taken into account that process variables, such as the level of applied power, have an influence on the magnitude and extension of the ultrasonic effects. Therefore, the aim of this work was to assess the influence of the level of applied ultrasonic power on the LTD of apple, analyzing the drying kinetics and the quality of the dried product. For that purpose, apple (Malus domestica cv. Granny Smith) cubes (8.8mm side) were dried (2m/s) at two different temperatures (10 and -10°C), without and with (25, 50 and 75 W) US application. In the dried apple, the rehydration kinetics, hardness, total phenolic content, antioxidant capacity and microstructure were analyzed to evaluate the impact of the level of applied ultrasonic power. At both temperatures, 10 and -10°C, the higher the ultrasonic power level, the shorter the drying time; the maximum shortening of the drying time achieved was 80.3% (at -10°C and 75 W). The ultrasonic power level did not significantly (p<0.05) affect the quality parameters analyzed. Therefore, US could be considered a non-thermal method of intensifying the LTD of fruits, like apple, with only a mild impact on the quality of the dried product.
authors.affiliation: Grupo ASPA, Departamento de Tecnología de Alimentos, Universitat Politècnica de València, Camí de Vera s/n, E46022 València, Spain.
authors.forename: J V
authors.initials: JV
authors.lastname: Santacatalina
authors.affiliation: Grupo ASPA, Departamento de Tecnología de Alimentos, Universitat Politècnica de València, Camí de Vera s/n, E46022 València, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Contreras
authors.affiliation: Grupo de Ingeniería de Alimentos, Departamento de Química, Universitat de les Illes Balears, Crta. Valldemosa, km. 7.5, E07122 Palma de Mallorca, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Simal
authors.affiliation: Grupo ASPA, Departamento de Tecnología de Alimentos, Universitat Politècnica de València, Camí de Vera s/n, E46022 València, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Cárcel
authors.affiliation: Grupo ASPA, Departamento de Tecnología de Alimentos, Universitat Politècnica de València, Camí de Vera s/n, E46022 València, Spain. Electronic address: jogarpe4@tal.upv.es.
authors.forename: J V
authors.initials: JV
authors.lastname: Garcia-Perez
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D003890:Desiccation / Q000379:methods*; D006244:Hardness; D007700:Kinetics; D027845:Malus / Q000737:chemistry; D013696:Temperature; D000069453:Ultrasonic Waves
chemical_list: D000975:Antioxidants
keywords: Dehydration; Drying kinetics; Modeling; Power ultrasound; Quality