Numerical analysis of rectangular type batch ohmic heater to identify the cold point

Perspectives on Novel Technologies of Processing and Monitoring the Safety and Quality of Prepared Food Products

With the changes of lifestyles and rapid growth of prepared food industry, prepared fried rice that meets the consumption patterns of contemporary young people has become popular in China. Although prepared fried rice is convenient and nutritious, it has the following concerns in the supply chain: (1) susceptible to contamination by microorganisms; (2) rich in starch and prone to stall; and (3) vegetables in the ingredients have the issues of water loss and discoloration, and meat substances are vulnerable to oxidation and deterioration. As different ingredients are used in prepared fried rice, their food processing and quality monitoring techniques are also different. This paper reviews the key factors that cause changes in the quality of prepared fried rice, and the advantages and limitations of technologies in the processing and monitoring processes. The processing technologies for prepared fried rice include irradiation, high-voltage electric field, microwave, radio frequency, and ohmic heating, while the quality monitoring technologies include Raman spectral imaging, near-infrared spectral imaging, and low-field nuclear magnetic resonance technology. These technologies will serve as the foundation for enhancing the quality and safety of prepared fried rice and are essential to the further development of prepared fried rice in the emerging market.

Application of Ohmic-Vacuum Combination Heating for the Processing of Senior-Friendly Food (Multiphase Food): Experimental Studies and Numerical Simulation

The popularity of senior-friendly food has been increasing as the world enters the age of an aging society. It is required that senior-friendly food products are processed with the new concept of processing techniques that do not destroy the nutritional and sensory values. Ohmic heating can be an alternative to conventional heating methods for processing senior-friendly food with retaining excellent taste and quality because of less destruction of nutrients in the food. In this study, the ohmic–vacuum combination heating system was developed to process a multiphase type of senior-friendly food. Changes in physical and electrical properties of senior-friendly model foods were investigated depending on the experimental conditions such as vacuum pressure intensity and vacuum pretreatment time. Numerical simulations based on the experimental conditions were performed using COMSOL multiphysics. The ohmic–vacuum combination heating method with agitation reduced the heating time of the model food, and non-uniform temperature distribution in model food was successfully resolved due to the effect of vacuum and agitation. Furthermore, the difference was found in the hardness of solid particles depending on the vacuum treatment time and intensity after the heating treatment. The ohmic–vacuum combination heating system appeared effective when applying for the senior-friendly foods in multiphase form. The simulation results matched reasonably well with the experimental data, and the data predicted through simulation could save the cost and time of experimentation.

Mathematical modeling of ohmic heating for inactivation of acid-adapted foodborne pathogens in tomato juice

The objective of the present study was to predict the inactivation trends of acid-adapted foodborne pathogens in tomato juice by ohmic heating through a numerical analysis method. The mathematical model based on finite element method (FEM) was used to simulate the multiphysics phenomena including electric heating, heat transfer, fluid dynamics, and pathogen inactivation. A cold spot was observed in the corner part of the ohmic heating chamber, where some pathogens survived even though all pathogens were inactivated elsewhere. Challenges of this study were how to reflect the increased resistance of pathogen by acid-adaptation. After simulation, we verified that inactivation level of acid-adapted foodborne pathogens by 25 Vrms/cm ohmic heating (1 kHz), predicted with the developed mathematical model, had no significant differences with experimental results (p > 0.05). Therefore, the mathematical approaches described in the present study will help juice processors determine the processing conditions necessary to ensure microbial safety at the cold point of a rectangular type batch ohmic heater.