Mathematical modelling of heat and mass transfer during frying of a methylcellulose coated dough.

N. ZARITZKY, R. BERTOLINI SUAREZ, M. A. GARCÍA

Rio de Janeiro, Brasil

Congreso; 2nd Mercosur Congress on Chemical Engineering,4th Mercosur Congress on Process Systems Engineering; 2005

 An edible methylcellulose (MC) coating, showing thermal gelation properties, was applied to reduce oil uptake during frying of a dough system formulated with wheat flour. Coating formulation included 1% MC and 0.75% sorbitol as plasticizer. Dough samples were dipped in the coating suspensions and immediately fried. Lipid content (LC) of fried products was determined on dried samples using a combined technique of successive batch and semicontinuous Soxhlet extractions. For coated dough discs the oil uptake  reduction was 30% compared to uncoated ones; MC coating did not modify water content of the samples. Quality attributes of fried dough such as color and texture were measured along the experiments. Thermal histories of coated and uncoated samples were obtained using thermocouples located at the border and center of the samples. A mathematical model of the deep-fat frying process based on the simultaneous numerical solution of the heat and mass transfer differential equations under unsteady state conditions was solved. Water evaporation at the  solid-oil interface was considered  Temperature profiles, loss of water and oil uptake were measured as a function of frying time. Experimental data were used to validate the numerical model, that was also solved for the  coated systems introducing the permeability coefficient of oil in the  coating.