Modeling multiscale transport mechanisms, phase changes and thermomechanics during frying

• Published in: Food research international 2014-08, Vol.62, p.709-717
• Main Authors: Bansal, Harkirat S., Takhar, Pawan S., Maneerote, Jirawan
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Coefficients; Computer simulation; Food industries; Frying; Fundamental and applied biological sciences. Psychology; Gages; Heat and mass transfer; Mathematical modeling; Mathematical models; Moisture; Oil uptake; Porosity; Porous media transport; Rice
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2014.04.016

Simultaneous fluid flow (water, oil, and gas) along with heat transfer during frying affects the quality of food product. Hybrid mixture theory (HMT) based two-scale equations were solved using the finite element method to simulate transport processes during frying of rice crackers. The model was used to predict moisture and oil content, pore pressures, evaporation rates, elasticity coefficient and temperature distribution as a function of frying time and spatial coordinates inside a rice cracker. The average absolute differences between the experimental and predicted values of average moisture and oil content were 2.5% and 14%, respectively. Simulations showed that about 99% of the initial average moisture was lost in the first 40s when fried at 200°C. Oil absorption took place throughout the frying process and the final average fat content after 140s of frying at 200°C was 0.30 (g oil/g solids). Presence of negative gage pore pressure gradients at the center of the rice cracker geometry in the early stages of frying appeared to be the driving force for initiation of oil uptake. The range of gage pore pressure in the rice cracker during the frying process was between −20 and +15kPa. Overall temperature of the rice cracker rose to that of frying temperature in 60s. The maximum coefficient of elasticity of the order of 107Pa was obtained at 40s of frying. HMT based model was suitable for simulating the heat and mass transfer mechanisms during frying. •Hybrid mixture theory provided a rigorous framework to model frying.•Capillary pressure in not only oil, but also water played a critical role.•Negative pore pressure developed inside rice crackers during frying.•Oil uptake is expected to have started during frying stage itself.