88C-18 |
Characterization and modeling of dielectric properties of turkey meat |
O. SIPAHIOGLU, Food Science and Technology, The Ohio State University, 2015 Fyffe Court, Columbus, OH 43210 and S. A. Barringer. The heating patterns produced during microwave heating of foods, both during cooking and reheating, can be modeled using the dielectric properties. Such knowledge is not only important for formulation of foods for microwave cooking but also is essential for modeling and validation of industrial microwave processing of foods. Sodium tripolyphosphate, salt, glycerol, sodium lactate, and lactic acid are functional additives that may be used to extend the shelf life of meat products such as turkey, but will also change the dielectric properties. Our objective was to create equations predicting the dielectric properties of turkey as a function of temperature, moisture and ash content of the samples, and determine the effects of glycerol and lactic acid on the dielectric properties. Samples were prepared by tumbling turkey meat in brine containing different concentrations of sodium lactate, glycerol and lactic acid. The samples were collected raw and dried to a water activity of 0.90 or 0.84. The dielectric properties of the samples were measured at 2450MHz using an open ended coaxial probe and a network analyzer. Water activity was determined using Aqualab aw analyzer, moisture and ash content by vacuum and ashing ovens. For the raw samples, the dielectric properties can be modeled by: K'=mwater(-0.21-0.001T)+mash(-1.21)+72.88, R2=0.61 K''=mwater(1.69-0.0003T+0.000014T2)+mash(3.22+0.13T)-101.09, R2=0.93 For the dried samples, the dielectric properties can be modeled by: K'=mwater(0.134+0.003T)+mash(-3.83)+33.24, R2=0.71 K''=mwater(1.16-0.0014T+0.00004T2)+mash(-0.605+0.033T)-35.60, R2=0.93 Use of water activity produced a similar fit. The dielectric loss factor was more accurately modeled than the dielectric constant. Glycerol affected the dielectric properties by changing the moisture content while lactic acid decreased the pH, denaturing proteins which decreased the moisture content and therefore the dielectric properties. Salt and free water had a strong effect on the dielectric properties. The predictive equations can be used for determining temperature profiles during microwave heating.
Session 88C, Food Engineering: Physical and Chemical Properties
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