29E-14 |
Effect of four different flours on the properties of donuts during the frying process |
J. F. Vélez-Ruiz1, M. E. SOSA-MORALES1, and R. Treviño-Cuevas2. (1) Chemical and Food Engineering, Universidad de las Américas - Puebla, Ex-Hda. Sta. Catarina Mártir, Cholula, Puebla, 72820, Mexico, (2) Chemical and Food Eng. Dept., Universidad de las Américas, Puebla, Sta. Catarina Mártir, Cholula, Puebla, Puebla, MEXICO, 72820 Frying is a traditional way for food preparation; there are many fried food items with desirable physical and sensory attributes for consumers. This process develops physicochemical changes and presents engineering challenges due to the applied high temperatures and combined heat and mass transfer mechanisms performed through the cooking process, donuts mainly made from wheat flour are baked products with a frying process as the final stage. Therefore, the purpose of this work was to study the effect of three oil temperatures (180, 190 and 200°C) and different residence times on the donut characteristics employing four different flours in the formulation. Donuts were prepared from a commercial formulation, utilizing different percentages of wheat, integral wheat, oats and amaranth flours. Once the dough was obtained, the frying process, that takes 90 s inside the container with 4.5 L of soybean oil, of the donuts was monitored, taking samples each 15 s. A factorial design including three factors (flour type, oil temperature, residence time) was followed during the experiment. Measuring several physicochemical characteristics in the donuts monitored the effect of each formulation, temperature and process time: color, density, dimensions, fat and moisture contents, temperature, and texture. The water loss as a function of time, showed similarities to the drying phenomenon, being the final moisture lower for wheat and higher for amaranth. The water diffusion coefficient was evaluated from an analytical solution for a hollow cylinder, finding a range of 3.9-33 x 10-7 m2/s depending of the formulation and temperature. Higher diffusion was related to the initial frying stage and high oil temperature, whereas lower coefficient values were related to final processing conditions and 180ºC. The donuts with 8% of oil at the beginning, exhibited different adsorption rates, varying with the flour type, and being higher for integral wheat and lower for amaranth.
Session 29E, Food Engineering: Transport processes and kinetics
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