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M. A. RAO, Food Science & Technology, Cornell Univ., New York State Agricultural Experiment Station, 630 W. North St., Geneva, NY 14456-1371 The rheological behavior of gelatinized starch dispersions (GSDs) is governed by the amount of leached amylose and state of the starch granules. The latter depends on a number of factors, such as: cross-linking, and variables during heating: rate of heating, temperature, shearing conditions, as well as the presence of a cosolute and its characteristics (e.g., molecular size). When the granules are intact, their volume fraction, which depends on the starch concentration (c) and extent of granule swelling (Q), plays a significant role on apparent viscosity of GSDs. However, the leached amylose also plays an important role in the rheology of GSDs. Further, synergistic or antagonistic interaction between amylose and the repeating unit of a gum would be important. Often, apparent viscosity of a food gum dispersion can be related to its concentration and molecular weight. The conformation, thus molecular size, of charged gum molecules is affected by the pH and ionic strength of a fluid. Thus different types of starch-gum physical structures may be formed in which granule-granule and granule-gum/amylose interactions would play important roles. Small and large-strain, and continuous flow rheological tests should help provide clues to the nature of those interactions. Results of recent systematic studies on rheological behavior of starch-gum systems will be covered.
Session 4, Impact of starch-hydrocolloid interactions in food systems
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