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Mathematical modeling of convective drying of yacon slices (Smallanthus sonchifolius)

Grant number: 18/21327-1
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): March 01, 2019
Effective date (End): February 28, 2021
Field of knowledge:Agronomical Sciences - Food Science and Technology
Principal Investigator:Carmen Cecilia Tadini
Grantee:Bianca Cristine Marques
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:13/07914-8 - FoRC - Food Research Center, AP.CEPID
Associated scholarship(s):19/21832-0 - Mathematical modeling of convective drying of yacon slices(Smallanthus sonchifolius), BE.EP.DR


This project aims to find optimal conditions for convective yacon drying, establish and validate kinetic parameters for the process, and model it using a commercial simulator (Comsol). For that purpose, transient conditions will be studied, considering changes in dimensions and thermophysical properties. Yacon is a plant cultivated originally in South America for its tuberous, mildly sweet roots. Its low amount of sucrose and glucose and high amount of non-digestible carbohydrates makes the yacon a good option for low- carbohydrate diets. Yacon is among the foods with the highest amount of Fructo-Oligossacharides (FOS) and inulin in nature. Effects of FOS and inulin ingestion in humans include modulation of the gut microflora, enhanced resistance to infections, improved calcium absorption, modulation of appetite and reduction of serum triglycerides. However, shelf life of yacon is limited to about seven days at ambient temperature, due to its high water content. Browning, hydrolysis of FOS and spoilage by microorganisms are the most common problems, which may be avoided by a treatment before storage. Convective drying of yacon roots is an option, considering that after the process, the resulting dried roots still have inulin and FOS, even if the roots are blanched prior to drying. This project will be developed in three steps- drying, modelling, and simulation. Drying operation will be carried out in conditions validated beforehand 14: between 50°C and 60°C, air relative humidity between 10% and 20%, and air velocity of 4 m/s. The convective dryer has a built-in system to control air temperature, relative humidity and velocity inside the chamber. Shrinking and structural changes will be measured in real time on a slice using a Greenough Leica S6D microscope, and mass loss will be measured by scales attached to trays in the chamber. All properties will be compared to results of predictions in the literature, and used in the software if applicable. Kinetics parameters and properties data will be used for modelling and simulating the drying process. Finally, the simulation will be validated using further experiments. Modelling step will be carried out in two dimensions (cylindrical coordinates), considering heat and mass transfer (not moment), in a conjugated macroscale model, for numeric resolution with finite elements method. For the simulation, material properties and dimensions will be initially considered constant; later, variable properties will be introduced, and results will be compared. (AU)