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In the past two decades, aseptic processing has been implemented in the food industry to sterilize particulate liquid food mixtures. To ensure that particulates in the liquid receive sufficient heating, mathematical modeling is employed to evaluate the temperature and lethality level in the particles. We developed a model for the thermal processing of liquid foods containing cubic particles in a continuous laminar pipe flow system, comprising a tubular heat exchanger. In our simplified approach, heat transfer equations for particulate liquid foods were solved analytically and numerically to evaluate the effect of certain process parameters on the time temperature profiles of particles and the lethality value in the products. A comparison of the particles’ lethality values was made between the experiment and simulation for two different particle residence times in a case study, and the model predictions were in good agreement with experimental data. Based on modeling studies, it was found that within the range of parameters studied, an increase in flow rate and particle size resulted in a decrease in the lethality value of the particles, while an increase in particle concentration and holding tube length resulted in the opposite effect.

The conveying process of a food solid-liquid system in a bent horizontal pipe was investigated using the multiphase Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach. The simulations were performed with commercial software tools, namely ANSYS Fluent and EDEM. The shape of the food particles was modelled as a cubic with a multi-sphere model, and a drag equation particle was used to consider also the effect of non-spherical particles. The simulations were performed for 5 mm size peach particle with different suspension flow velocities (0.3 and 0.8 m/s) and particle mass concentrations (5%, 10%, and 30%). The comparison between experimental and simulated particle velocity profiles demonstrated that, despite some quantitative discrepancies, the CFD-DEM modelling yielded a good agreement with the experimental data and could capture the experimental trends. In addition, this simulation approach could provide valuable information about particle flow properties such as velocity and position, that are difficult to measure experimentally.

Drying is one of the popular preservation methods in food products. This work was done to investigate the influence of the drying temperatures and methods on the drying characteristics of ‘ikanbakar’ paste. The ‘ikanbakar’ paste was dried by using oven drying and vacuum drying methods at temperatures of 50°C, 60°C and 70°C. The drying rate was estimated from the moisture content and drying time data. The drying curve showed the falling rate period as the drying rate decreased with increasing time. For colour analysis of the paste, the L* values from the oven drying method were lower than those from the vacuum drying method, ranging from 7.4210 to 7.2752. This showed that the colour of paste from oven drying was darker than vacuum drying. The mathematical models used to describe the drying curve of ‘ikanbakar’ paste were Lewis, Page, Two-term, and Midilliet. al. model. The performance of these models was evaluated by comparing their root mean square error (RSME) and chi-square (X²) values, and it was found that the most suitable model was the Two-term model. There were insignificant differences between the effective moisture diffusivity (Deff) values for the ‘ikanbakar’ paste in both drying methods.