Application of non-isothermal simulation in optimization of food drying process

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ORIGINAL ARTICLE

Application of non-isothermal simulation in optimization of food drying process Habibeh Nalbndi1 • Sadegh Seiiedlou1 • Babak Alizadeh2

Revised: 1 August 2020 / Accepted: 18 August 2020  Association of Food Scientists & Technologists (India) 2020

Abstract The application of numerical methods on one hand and simulation of various food processing techniques on the other hand could be effective methods in the process optimization such as reducing energy consumption and processing time and increasing product quality. The objective of this study was to apply variable air temperatures during drying process of garlic slices while reducing the drying time and maintaining the highest possible quality of the dried product. Therefore, drying process was simulated based on the numerical methods, and the proper time to change the air temperature was predicted using the product temperature profile. A high air temperature was applied at the beginning of the drying process (70 C) and then during the process the temperature was decreased (50 C) in a way that that the product surface temperature was never increased more than the critical temperature of 50 C. The result of simulation was validated based on experiments at various drying conditions such as air temperature of 50, 60 and 70 C and slice thickness of 2.5 mm. Based on the results of the study, by applying the variable air temperatures during drying process on samples, the drying time was reduced by 24% and the color quality of the samples was preserved. The final product produced by this method had higher quality (total color changes is 3.278) compared to the products dried at the higher constant temperature of 70 C (total color changes is 6.71).

& Habibeh Nalbndi [email protected]; [email protected] 1

Department of Biosystem Engineering, Faculty of Agriculture, University of Tabriz, Tabriz, Iran

2

Department of Biosystems (BIOSYST), Faculty of Bioscience Engineering, 3001 Louvain, Belgium

Keywords Food color  Drying  Garlic  Numerical simulation  Product quality  Variable air temperature List of Aal aw C Cp DAB D0 Ea hm kp Km Kg L Lv M n DP Patm Ps Psat P? MR R RHa x, y, z t T Tinf Ts qa qp

symbols Aluminum surface (m2) Water activity Moisture content (kgwater/kgdry matter) Specific heat of garlic (J/(kg K)) Effective moisture diffusivity in gas phase (m2/s) Pre-exponential factor of Arrhenius equation Activation energy (J/mol) Heat transfer coefficient (W/(m2 K)) Thermal conductivity of garlic (W/(mK)) Mass transfer coefficient at surface (m/s) Mass transfer coefficient at surface (s/m) Half thickness of slice (m) Latent heat of evaporation (J/kg) Mass (kg) outward normal to the surface Pressure difference (Pa) Atmosphere pressure (Pa) Vapor pressure in the food surface (Pa) Saturation vapor pressure (Pa) Vapor pressure in the hot air (Pa) Moisture ratio Universal gas constant (8.314 J/(mol K)) Relative humidity of air (%) Coordinates (m) Time (s) Temperature (K) Drying air temperature (K) The surface temperature of slice