17H-13 |
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G. H. LEE1, H. E. Huff2, and F. Hsieh2. (1) Division of Agricultural Engineering, Kangwon National Univ., Chuncheon, 200-701, South Korea, (2) Dept. of Biological Engineering, Univ. of Missouri, 254 Ag. Eng. Bldg., 1406 E. Rollins St., Columbia, MO 65211-5200 Twin-screw extruders can effectively texturize and shape a wide range of ingredients in a continuous operation. In recent years, they have been used to produce fibrous soy protein meat analog under high moisture (>50%) extrusion conditions. The magnitude of the equivalent heat transfer coefficient in the cooling die will influence the design of the cooling die for the process scale-up. The objectives of this study were to estimate the equivalent overall heat transfer coefficient (Ue) between the extruded product and the cooling die and to predict the product temperature at the die outlet with the estimated value of Ue. The experimental design consisted of two cooling die width (30 and 60 mm), two cooling die length (100 and 300 mm), four product moisture content (71.2, 67.0, 61.6 and 55.8% wb), and two cooling media (water or water plus ethylene glycol). The height of the cooling die was fixed at 10 mm. The ingredients of the meat analog were soy protein isolate (60%) and wheat gluten (40%). The extruder temperature profiles were 50, 100, 150, and 170°C. The equivalent overall heat transfer coefficients (Ue) between the extruded product and the cooling die were estimated by measuring the bulk product temperatures and cooling medium temperatures before entering and after exiting the cooling die. The product temperatures at the die outlet were predicted with the estimated values of Ue. When water was used as cooling medium, the values of Ue varied from 0.560 to 0.809 kW/m²K and from 0.505 to 0.709 kW/m²K for 30 and 60 mm die widths, respectively, at four different moisture contents. With using water plus ethylene glycol as cooling material, the estimated values of Ue were ranged from 0.597 to 0.947 kW/m²K and from 0.520 to 0.785 kW/m²K for 30 and 60 mm die widths, respectively, depending on the product moisture content. Predicted product temperatures at the die outlet were within 7ºC of measured experimental values. The values of Ue were linearly proportional to the moisture content of the extruded product.
Session 17H, Food Engineering: Thermal processes
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