88C-5 |
Application of state diagram to pasta processing |
L. E. FIRST, Food, Agricultural, and Biological Engineering, The Ohio State University, 590 Woody Hayes Dr., Columbus, OH 43210 and G. Kaletunç. Drying, tempering, and cooling are critical steps in pasta production. An uneven moisture distribution in pasta during these stages causes the formation of local domains with different physical states. The resultant stress development, leads to checking and breakage during storage. Determination of the physical state of pasta as a function of temperature and moisture content simulating pasta production is essential for designing optimal processing conditions to produce high quality pasta. The objective is to develop a two dimensional state diagram for pasta and map the path of pasta processing on the state diagram to evaluate the impact of drying, tempering, and cooling on pasta properties. Water and semolina dough is extruded at 49°C and 14.6 rpm. Pasta is dried with high temperature, ultra-high temperature, and hot air/microwave methods. Fresh pasta is equilibrated under six relative humidity environments between 11% and 93%. Thermally-induced transitions are determined with standard and modulated differential scanning calorimeter. State diagrams are constructed plotting the melting and glass transition curves of pasta as a function of moisture content. Path of pasta processing, including three drying protocols, is superimposed on the state diagram. Semolina is initially in a glassy state. Upon mixing with water, the resulting dough is in a rubbery state and remains in this state through the extrusion and drying process. During tempering and cooling, pasta goes through its glass transition temperature around 50°C and 10% moisture, and settles in the glassy state. The difference between the drying temperature and the glass curve affects the quality attributes of the end product. In the absence of knowledge about physical properties of materials as a function of processing conditions, optimum processing conditions are determined by trial and error. Development of state diagrams provides a rational basis for designing processing conditions without costly trial and error runs.
Session 88C, Food Engineering: Physical and Chemical Properties
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