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The knowledge of the dielectric properties of oils is of great importance for several industrial applications, such as microwave-assisted oil frying for foods and high voltage electric power transmission. In this paper, we present the complex permittivity of vegetable oils (canola, olive, soybean, coconut) at 2.50 GHz using the cavity perturbation technique from 28 to 200 °C (temperature close to the smoking point of oils). The measurements were taken with a cylindrical cavity operating at the TE 111 mode with an unloaded Q of 4950. In addition, free fatty acids, peroxide index and color were measured before and after heating., (© Association of Food Scientists & Technologists (India) 2020.)

The dielectric properties and specifically the complex relative permittivity of foods are key elements for the design of pasteurization processes with high frequency electromagnetic waves. Mexican sauces are recognized worldwide for their flavor and nutritional properties. In this work, the complex permittivity of four of the most representative sauces of Mexican cuisine (chipotle chili, habanero chili, red and green sauce) is presented. The permittivity was measured with the open coaxial probe method at temperatures of 25, 40, 55, 70, 85 °C and in the frequency range of 500 MHz to 6 GHz. Additionally, moisture content, specific heat, viscosity, water activity, density and electrical conductivity are reported, these last three at 25 °C. Dielectric properties were affected by the sauce formulation. The loss factor of each sauce sample at any temperature presents significant changes in relation to the frequency. At 915 and 2,450 MHz, d ε ' ' d T > 0 , which would cause a thermal runaway effect or the uncontrolled rise in temperature in the sauces during the microwave pasteurization. At 5,800 MHz, d ε ' ' d T < 0 , which would give better control for microwave heating than at 915 and 2,450 MHz. At 915 MHz, the loss factor of all sauces is higher than at 2,450 and 5,800 MHz, therefore, more rapid heating can be produced. Moreover, at 915 MHz, microwaves exhibit higher penetration depth than at 2,450 and 5,800 MHz; therefore, at 915 MHz, the greatest uniform microwave dielectric heating would be achieved. Thus, 915 MHz is the frequency recommended for the studied sauces pasteurization. PRACTICAL APPLICATION: This work provides the dielectric properties of Mexican sauces at different temperatures and their penetration depths in the microwave range, which are key information for further microwave-assisted pasteurization process and for getting safer sauces for consumers. Moreover, this research supplies suggestions about what frequency for ISM (Industrial, Scientific and Medical) applications is the best for microwave-assisted pasteurization according to the penetration depth of the electromagnetic wave in the sauces and microwave dielectric heating speed of the sauces., (© 2020 Institute of Food Technologists®.)

For microwave heating pasteurization processes, knowledge of the dielectric characteristics of foods are very important. In this paper, we present the dielectric properties of raw soy milk and commercial packed soy milk of four different flavors (light, natural, chocolate and pecan) from 500 MHz to 20 GHz, covering most of the assigned frequencies by the Federal Communications Commission for heating purposes. Experiments were performed using an open-ended-coaxial probe and a vector network analyzer. This characterization was carried out for temperatures ranging from 20 to 70 °C in steps of 10 °C. The dielectric constant of soy milks decreased with increasing frequency, while increasing temperature resulted in decreasing of the values. The dielectric loss factor presents a U shape behavior, where the loss started decreasing from 500 MHz to about 3 GHz and then, it increased again up to 20 GHz. In addition, higher temperatures decreased the dielectric loss. Applying the higher order Debye´s equation, two relaxation times were calculated for the soymilks, with good agreement with the measured properties. Deeper penetration of microwaves were obtained for raw soy milk at 915 MHz, making it suitable for microwave pasteurization.

Purpose: To evaluate the prognostic relevance of tumor size as determined on Magnetic Resonance Imaging (MRI) in cervical cancer., Methods and Materials: A total of 70 consecutive patients were included in the study. 15 patients underwent surgery alone (Group A), 27 patients underwent surgery followed by adjuvant radiation (Group B), 14 patients underwent concomitant chemo radiation (Group C), and 14 patients underwent radical radiation alone (Group D). External radiation was delivered followed by intra cavitary brachytherapy. Serial MRI scans were performed in all patients before and after completion of treatment on a 1.0 Tesla MRI scanner. Patients were divided into three groups based upon MR volumes 100 cc. A correlation between MR volume, FIGO stage, disease free survival (DFS) and overall survival (OS) was done. Disease free and overall survivals were calculated using Kaplan Meier survival curves according to stage, MR volume and treatment protocol., Results: In group I (MR volume 100 cc), 57% patients had stage II, 14% had stage III and 29% patients had stage IV disease. The DFS and OS did not achieve a level of statistical significance when evaluated as per protocol [DFS at p = 0.0685 and OS p = 0.3242], however a statistical significance was seen when DFS and OS were evaluated according to MR volumes [DFS, p = 0.0015 and OS, p = 0.0001]., Conclusion: In cervical cancer, the volume of disease as assessed on MRI may be a better prognostic indicator than FIGO staging and needs further evaluation.