The Effect of Heating Rate by Ohmic Heating on Rheological Property of Corn Starch Suspension

Ohmic Heating에 의한 가열속도 변화가 옥수수전분의 물성특성에 미치는 영향

  • Lee, Seok-Hun (Department of Food Science, Chungkang College of Cultural Industries) ;
  • Jang, Jae-Kweon (Department of Food Science, Chungkang College of Cultural Industries) ;
  • Pyun, Yu-Ryang (Department of Biotechnology, Yonsei University)
  • 이석훈 (청강문화산업대학 식품과학과) ;
  • 장재권 (청강문화산업대학 식품과학과) ;
  • 변유량 (연세대학교 생명공학과)
  • Published : 2005.06.30

Abstract

Granule swelling is essential phenomenon of starch gelatinization in excess water, and characteristic of heated starch dispersion depends largely on size and distribution of swelled starch granule. Although swelling characteristic of starch granules depends on type of starch, heating rate, and moisture content, influence of heating rate on swelling phenomenon of starch granule has not been fully discussed, because constant heating rate of starch dispersion cannot be obtained by conventional heating method. Ohmic heating, electric-resistant heat generation method, applies alternative current to food materials, through which heating rate can be easily controlled precisely and conveniently at wide range of constant heating rates. Starch dispersion heated at low heating rates below $7.5^{\circ}C/min$ showed Newtonian fluid behavior, whereas showed pseudoplastic behavior at heating rates above $16.4^{\circ}C/min$. Apparent viscosity of starch dispersion increased linearly with increasing heating rate, and yield stress was dramatically increased at heating rates above $16.4^{\circ}C/min$. Average diameter of corn starch granules during ohmic heating was dramatically increased from $30.97\;to\;37.88\;{\mu}m$ by increasing heating rate from $0.6\;to\;16.4^{\circ}C/min$ (raw corn starch: $13.7\;{\mu}m$). Hardness of starch gel prepared with 15% corn starch dispersion after heating to $90^{\circ}C$ at different heating rates decreased gradually with increasing heating rate, then showed nearly constant value from $9.4\;to\;23.2^{\circ}C/min$. Hardness increased with increase of heating rate higher than $23.2^{\circ}C/min$.

Keywords

ohmic heating;corn starch;heating rate;rheology

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