Density and Porosity in Drying Starch Materials

Authors

  • S.N. MAROUSIS,

    1. Author Saravacos is with the Dept. of Food Science and Center for Advanced Food Technology, Cook College, New Jersey Agricultural Experiment Station, Rutgers, the State Univ., New Brunswick, NJ 08903. Author Marousis is with Procter & Gamble Company, Process Technology Dept, Cincinnati, OH 45232.
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  • G.D. SARAVACOS

    1. Author Saravacos is with the Dept. of Food Science and Center for Advanced Food Technology, Cook College, New Jersey Agricultural Experiment Station, Rutgers, the State Univ., New Brunswick, NJ 08903. Author Marousis is with Procter & Gamble Company, Process Technology Dept, Cincinnati, OH 45232.
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  • New Jersey Agricultural Experiment Station publication No D-10535-1-89, supported by State funds and the Center for Advanced Food Technology. The Center for Advanced Food Technology is a New Jersey Commission on Science and Technology Center. The technical help of Kiran Shah on particle density and size measurement is acknowledged.

ABSTRACT

The particle density of granular and gelatinized corn starches was determined in the moisture range 0 to 1 kg water/kg dry solids, using a gas stereopycnometer. The bulk porosity (void fraction) of spherical starch samples at various moisture contents was estimated from the bulk and particle densities during air drying at 60°C. The particle density data fitted a polynomial function of moisture content (X), passing through a maximum value of 1500 kg/m3 at X = 0.15. The bulk porosity of the starch samples increased linearly during drying, reaching a value of 0.45 near dryness. Differences in structure between granular and gelatinized starches during drying were observed by stereomicroscopy. The changes in porosity could be related to variations of the effective moisture and thermal diffusivities of starch materials.

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