Browsing by Subject "Dielectric heating"

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    Modeling of radio frequency heating of packed fluid foods moving on a conveyor belt: A case study for tomato puree
    (Elsevier, 2023-05-20) Abea, Andrés; Kravets, Marina; Gou, Pera; Guàrdia, Dolors; Felipe, Xavier; Bañón, Sancho; Muñoz, Israel; Tecnología de Alimentos, Nutrición y Bromatología
    Computer simulation models were used to study radiofrequency heating of liquid foods moving on a conveyor belt between staggered-through field electrodes of non-uniform electric field distribution. Voltage across the electrodes was estimated using a finite-element model and a one-dimensional model, and these were utilized to simulate heating of tomato puree mixtures of varying dielectric and thermal properties, at various nominal voltages and electrode gaps. The experimental results for volume average temperatures showed good agreement with the outcome of both simulation models. Although the temperature profiles indicate a concentration of heat at the bottom and edges of the bottle, natural convection and the shape of the container helped mitigate heat localization. It was determined that, while simple models could provide accurate volume average temperatures,incorporating convectively enhanced conductivity was necessary to accurately predict temperature distribution. The heating rate was found to decrease with an increase in salt concentration.
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    Validation of Pasteurisation Temperatures for a Tomato–Oil Homogenate (salmorejo) Processed by Radiofrequency or Conventional Continuous Heating
    (MDPI, 2023-07-26) Kravets, Marina; Cedeño-Pinos, Cristina; Abea, Andrés; Guàrdia, Dolors; Muñoz, Israel; Bañón, Sancho; Bañón, Sancho; Tecnología de Alimentos, Nutrición y Bromatología
    Salmorejo is a viscous homogenate based on tomato, olive oil and breadcrumbs commercialised as a “fresh-like” pasteurised–chilled purée. Due to its penetration, dielectric heating by radiofrequency (RF) might improve pasteurisation results of conventional heating (CH). The objective was to val-idate the pasteurisation temperature (70–100 °C, at 5 °C intervals) for salmorejo processed by RF (operating at 27.12 MHz for 9.08 s) or conventional (for 10.9 s) continuous heating. The main heat-induced changes include: orangeness, flavour homogenisation, loss of freshness, thickening, loss of vitamin C and lipid oxidation. Both CH and RF equivalent treatments allowed a strong re-duction of total and sporulated mesophilic microorganisms and an adequate inhibition of the pectin methylesterase, peroxidase and, to a lesser extent, polyphenol oxidase but did not inhibit the pol-ygalacturonase enzyme. Pasteurisation at 80 °C provided a good equilibrium in levels of microbi-ological and enzymatic inhibition and thermal damage to the product. Increasing this temperature does not improve enzyme inactivation levels and salmorejo may become overheated. A “fresh-like” good-quality salmorejo can be obtained using either conventional or radiofrequency pasteurisers.