“Mathematical Modelling of Heat And Mass Transfer During Frying of a Methylcellulose Coated Dough"

BERTOLINI SUAREZ, R.; GARCIA, M.A.; ZARITZKY, N.

Rio de Janeiro, Brasil

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

The great volume of production of fried food and its influence on lipids consumption enhances the study of the frying process because of its economic and nutritional impact. Lipid content is related to obesity and coronary diseases; an alternative to reduce oil uptake in fried foods is the use of edible coatings with oil barrier properties. In the present work 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 for 10 seconds 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. The oil uptake reduction was 30% for coated dough discs compared to the 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. Colorimetric measurements were carried out with a Minolta colorimeter. Breaking force of samples was measured by puncture test using a Texture Analyzer TA.XT2i with a 5 kg cell; maximum force at rupture was determined from the force-defor mation curves. Thermal histories of coated and uncoated samples were obtained using thermocuples 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.