17G-4 |
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T. MOTWANI and R. C. Anantheswaran. Dept. of Food Science, Pennsylvania State Univ., 208 Borland Lab., University Park, PA 16802 The impact of ingredients and processes on dielectric properties is much needed for successful design of microwaveable foods and microwave processes for the food industry Starch and pectin are very commonly used ingredients, and they impact mobility of water and ionic concentrations within the food system. This in turn will affect the dielectric properties of starch-pectin systems. The objective of this study was to investigate the interaction between starch and pectin at various concentrations and the impact of gelatinization on the dielectric properties of these mixtures. Solutions of 0-10% corn starch (wt./wt.)(Argo Corn Starch, Bestfoods, NJ) were prepared and high methoxy rapid set pectin (Tic Gums, Belcamp, MD) at levels ranging from 0 – 2%(wt./wt.) was added. The solutions were stirred and then held at room temperature for hydration for 30 min. The dielectric properties were measured by a Network Analyzer (HP 85070A and HP 8572C, Hewlett Packard Co., Santa Rosa, CA) using an open-ended coaxial probe. The starch solutions were gelatinized by heating to 80°C. The solutions were then cooled to 20°C and their dielectric properties were measured again in the frequency range of 500-3000 MHz. The dielectric constant decreases with increase in concentration of starch, while the dielectric loss factor shows negligible variation within the range studied. At higher concentrations of starch, the addition of pectin further depressed the dielectric constant. The dielectric loss factor increased with concentration of pectin and increase was substantial at frequencies in the range of 500-1000MHz. Interesting changes were recorded in the dielectric constant of starch-pectin system after gelatinization. There was a general decrease in dielectric constant after gelatinization of starch-pectin solution. The addition of pectin at lower concentrations increased the loss factor on gelatinization, whereas increase in loss factor at higher pectin concentrations was relatively lower. The role of pectin and the effect of gelatinization on dielectric properties of starch systems will be described based on a mechanistic model and electromagnetic mixing formulas. Such a model can be successfully used to select ingredients for formulation of microwaveable foods.
Session 17G, Food Engineering: Physical, chemical and electrical properties
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