Rheological Properties Including Tensile Fracture Stress of Semolina Extrudates Influenced by Moisture Content

Authors

  • H. LIU,

    1. Authors Liu and Hayakawa are with the Dept. of Food Science, New Jersey Agricultural Experiment Station, Cook College, Rutgers-The State University, P.O. Box 231, New Brunswick, NJ 08903-0231. Author Qi is with the Dept. of Chemical & Biochemical Engineering, College of Engineering, Rutgers Univ., New Brunswick, NJ 08903.
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  • J. QI,

    1. Authors Liu and Hayakawa are with the Dept. of Food Science, New Jersey Agricultural Experiment Station, Cook College, Rutgers-The State University, P.O. Box 231, New Brunswick, NJ 08903-0231. Author Qi is with the Dept. of Chemical & Biochemical Engineering, College of Engineering, Rutgers Univ., New Brunswick, NJ 08903.
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  • K. HAYAKAWA

    1. Authors Liu and Hayakawa are with the Dept. of Food Science, New Jersey Agricultural Experiment Station, Cook College, Rutgers-The State University, P.O. Box 231, New Brunswick, NJ 08903-0231. Author Qi is with the Dept. of Chemical & Biochemical Engineering, College of Engineering, Rutgers Univ., New Brunswick, NJ 08903.
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ABSTRACT

Semolina extrudates were reshaped, immediately after extrusion to form 0.5 mm thick × 2 mm wide × 130 mm long strips. Moisture content (W) was adjusted to 5 to 39% (dry basis) equilibrating in desiccators containing saturated salt solutions. The following tensile rheological properties of the prepared samples were determined at room temperature (21-24°C) using a Rheometrics solid analyzer: Young modulus (E), yield stress (σy), fracture stress (σc) and fracture stain (ɛc). Each of E, σy and σc was fitted by a semilogorithmically linear function of W with a negative slope. The property ɛc fitted two semilogarithmically linear functions: for W < 24.2% a line with a positive slope and for W > 24.2% a line with near zero slope. Such data for moisture ranges used in conventional pasta drying can help to optimize conditions for pasta production without stress cracking.

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