Emerging technologies to improve food drying: ultrasound and ethanol on convective and infrared drying

• Autor(a) principal: Rojas Silva, Meliza Lindsay
• Data de Publicação: 2020
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/11/11141/tde-06032020-150533/
• topic: Convective drying; Etanol; Ethanol; Food properties; Infrared drying; Propriedades dos alimentos; Secagem convectiva; Secagem por infravermelho; Ultrasound; Ultrassom

Although food drying is one of the oldest preservation methods, there are still several limitations related with the quality of dried products (physical, chemical and nutritional properties), as well as related to the quality of processes (energy consumption and costs). The present thesis studied the application of different emerging technologies to improve food drying. For this purpose, different approaches such as microstructural study, kinetic evaluation, and physicochemical analyses were used to describe the process, food properties and composition. Firstly, the influence of elements that compose the plant microstructure was studied on relation to water transfer and physical properties. Based on the obtained results, it was evaluated the effect of emerging technologies (ethanol, high-power ultrasound and mechanical perforations) application as pre-treatments to the drying process (convective, infrared and ultrasound-assisted drying), as well as, on the food physical properties and composition. Finally, the pre-treatments used to improve drying was also used to incorporate microencapsulated nutrients (both hydrophilic and lipophilic) into the products to be dried, thus obtaining dry vegetable with improved nutritional content. The results show the complex structure of foods make them non-isotropic materials, where its microstructural elements influence the water transfer phenomena. The proposed pre-treatments reduced the conventional drying time. Different mechanisms responsible for improvements through the application of pre-treatments were formulated, based on macro and microstructural observations, as well as in the kinetic parameters describing the drying behaviour. Besides, other notable results were obtained, such as the decrease in energy consumption, improvements in the rehydration properties without negative changes in viscoelasticity and deformation, as well as better retention and incorporation of nutrients. Summarizing, this work intends to be a contribution to the better understanding of food drying and its implications, as well as to provide alternatives for its possible improvement.