Mathematical Modeling and Microbiological Verification of Ohmic Heating of a Multicomponent Mixture of Particles in a Continuous Flow Ohmic Heater System with Electric Field Parallel to Flow

Abstract

To accomplish continuous flow ohmic heating of a low-acid food product, sufficient heat treatment needs to be delivered to the slowest-heating particle at the outlet of the holding section. This research was aimed at developing mathematical models for sterilization of a multicomponent food in a pilot-scale ohmic heater with electric-field-oriented parallel to the flow and validating microbial inactivation by inoculated particle methods. The model involved 2 sets of simulations, one for determination of fluid temperatures, and a second for evaluating the worst-case scenario. A residence time distribution study was conducted using radio frequency identification methodology to determine the residence time of the fastest-moving particle from a sample of at least 300 particles. Thermal verification of the mathematical model showed good agreement between calculated and experimental fluid temperatures (P > 0.05) at heater and holding tube exits, with a maximum error of 0.6 °C. To achieve a specified target lethal effect at the cold spot of the slowest-heating particle, the length of holding tube required was predicted to be 22 m for a 139.6 °C process temperature with volumetric flow rate of 1.0 × 10(-4) m3/s and 0.05 m in diameter. To verify the model, a microbiological validation test was conducted using at least 299 chicken-alginate particles inoculated with Clostridium sporogenes spores per run. The inoculated pack study indicated the absence of viable microorganisms at the target treatment and its presence for a subtarget treatment, thereby verifying model predictions.

Application of ohmic heating for the inactivation of microbiological hazards in food products

“…In this regard, a Magnetic Resonance Imaging (MRI) mapping method was used to identify the temperature distribution during ohmic heating (Ye et al, 2003). Recently several studies have been published on combining mathematical modeling with microbiological validation (Choi, Kim, Park, Ahn, & Kang, 2020; Kamonpatana et al, 2013, 2013), which would be valuable for both the food industry and consumers. These attempts should further be applied to ohmic heating‐based hurdle technologies discussed in this review or developed in the future.…”

Development of Conductive Packaging for Beverage Processing by Ohmic Heating

“…Ohmic heating is an alternating thermal treatment, which passes electric current through the foods and immediately generates heat within the foods with great efficiency. The advantages of ohmic heating over conventional heat treatments are rapid and uniform heat through foods making ohmic heating commercially valuable for high-quality products [2][3][4]. However, available packaging is not appropriate for ohmic heating.…”

Ohmic Heating of an Electrically Conductive Food Package

“…Ohmic heating involves the channeling of an alternating current through food products, dissipating electrical energy into heat with a highly effective energy transfer (Jun and Sastry ; Lee and others ). It is acceptable for commercial production of high quality products while minimizing overcooking typical of conventional heat treatments (Kamonpatana and others , ).…”

“…The accuracy of mathematical models has been determined using the study of thermal verification (Sastry ; Chen and others ) by comparing the simulated and actual sample temperatures. Moreover, microbiological experiments via inoculated pack study (Somavat and others ; Kamonpatana and others , ) were introduced to validate the sterilization of foods. For example, Somavat and others () examined Geobacillus stearothermophilus spores (ATCC 5973) while Kamonpatana and others () investigated Clostridium sporogenes spores to ensure that foods after treatment were safe for human consumption.…”