Slowest heating zone migration for heterophase baby food system

В работе приведены результаты исследования миграции зоны наименьшего прогревания (Slowest Heating Zone, далее SHZ) в упаковке при термической стерилизации мелкодисперсной гетерофазной пищевой системы для питания детей раннего возраста. Локализация SHZ является основным параметром, на основе которого производится разработка режимов термической стерилизации для пищевых систем с конвективным теплообменом. В качестве объекта исследования использовали сок яблочный с мякотью для детского питания отечественного производства, который представляет собой гетерофазную систему с жидкой дисперсионной средой и равномерно распределенной в ней высокодисперсной фазой в виде частиц мякоти с плотностью, близкой к плотности жидкой среды. Продукт был расфасован в стеклянные банки III-52-190. Прогрев проводили в термостате при температурах греющей среды 75, 80, 85, 90 и 95 °C, которые поддерживали и регистрировали автоматически, что обеспечивало равномерность температурного поля воды в термостате. Кривые прогрева снимали с помощью термопары, рабочий спай которой размещался по оси банки на высоте 6, 12, 18, 24, 30, 36, 40, 42 и 48 мм от дна. В результате экспериментальных исследований процесса стерилизации установлено, что в подобной пищевой системе локализация SHZ и кинетика ее миграции аналогичны этим параметрам в гомофазных пищевых системах, но различаются важными особенностями, вызванными как наличием дисперсной фазы, так и различиями в теплофизических параметрах продуктов. Отмечено влияние обязательной для питания детей раннего возраста гомогенизации сока с мякотью на вязкость продукта из-за упорядоченности ориентации частиц мякоти, вызывающей миграцию SHZ при изменении температуры сока при нагреве и охлаждении. The paper presents the results of researches of Slowest Heating Zone (SHZ) migration in packaging during thermal sterilization of fine heterophasic food system for feeding young children. Localization of SHZ is the main parameter on the basis of which the development of thermal sterilization modes for food systems with convective heat exchange is made. As the object of the study, we used apple juice with pulp for baby food of domestic production, which is a heterophase system with a liquid dispersion medium and a highly dispersed phase uniformly distributed in it in the form of pulp particles with a density close to the density of the liquid medium. The product was packaged in glass jars III-52-190. Warming up was carried out in a thermostat at temperatures of the heating medium of 75, 80, 85, 90, and 95 °C, which were maintained and recorded automatically, which ensured the uniformity of the temperature field of water in the thermostat. The heating curves were recorded using a thermocouple, the working junction of which was located along the can axis at heights of 6, 12, 18, 24, 30, 36, 40, 42, and 48 mm from the bottom. As a result of experimental studies of the sterilization process, it was found that in such a food system, the localization of SHZ and the kinetics of its migration are similar to these parameters in homophase food systems, but differ in important features caused by both the presence of a dispersed phase and differences in the thermophysical parameters of products. The effect of homogenization of juice with pulp, obligatory for feeding young children, on the viscosity of the product due to the regularity of the orientation of pulp particles, which causes migration of SHZ when the temperature of the juice changes during heating and cooling, has been noted.

Numerical simulation of conductive heat transfer in canned celery stew and retort program adjustment by computational fluid dynamics (CFD)

In this study, conductive heat transfer was investigated during sterilization in the canned celery stew. A computational fluid dynamics CFD model was developed and validated to predict the temperature profiles and determine the slowest heating zone (SHZ) during the thermal processing. The temperature profile was obtained and recorded experimentally at a point where the coldest thermal point was expected. CFD models were validated against experimental data. The results of the study showed that the SHZ was located at the geometric center of the containers (x = 5.00, y = 1.42, z = 6.75 cm), and the temperature reached 119.5 °C. Root mean square error (RMSE) was calculated and showed a good fit between both methods (RMSE = 1.03). The container geometrical center F0 was estimated to be 13.19 min. For optimization of the process, according to the stew ingredients, especially meat, F0 was about 8 min. Thus, the required holding time was decreased by 5.19 min, and the retort setting was readjusted.

Influence of Rotation Speed on the Sterilization of a Steamed Liquid Food Can Using Numerical Simulation

This paper presents an efficient way for the sterilization of a liquid food (liquid soup) can lying vertically and rotated axially by using a commercial computational fluid dynamics package (ANSYS FLUENT). Aside from the forced convection applied by rotating the can, the simulation involved effect of the natural convection with steam heating to 121°C around all of the can sides. The liquid food in the can was assumed to have constant properties, except for the density (Boussinesq assumption) and viscosity (temperature dependent). By solving the governing equations of mass, momentum and energy, we compared the temperature profile in the thermal sterilization which emphasizes the slowest heating zone (SHZ) of viscous rotation speeds compared to that of a stationary can. The simulation results of temperature profiles with different rotation speeds (5, 10, 15, 20, and 25 rpm) for different periods (1, 19, and 43 minutes) indicated that the combined effect of natural and forced convection causes the higher temperature to reach all of the locations of the SHZ with increased rotational speed. With the higher rotational speed, the heating process time is further reduced when reaching the same lowest temperature at the SHZ of the liquid food can.

Heat Penetration Rates of Natural Convection Heating Liquids in Metal Containers

Heat penetration (HP) test data have been obtained for water in 13 sizes of metal cans and for 16 fluids with different physical properties in 211 × 400 metal cans. Data were collected until the slowest heating zone was less than 0.1 C° below the heating medium temperature. When conventional HP graphs were plotted, these natural convection heating liquids formed curves instead of straight lines. A straight line was fitted by least squares regression to the data between (T1 - T) values from 40.0 to 4.0, 10.0 to 1.0, 4.0 to 0.4, and 1.0 to 0.2 C° and the f-values determined. The results show that the f-value of fluids that heat by convection increase with heating time, indicating that the true shape of the heat penetration data on a semilogarithmic graph is a curve.

Heat Penetration Rates of Natural Convection Heating Liquids in Metal Containers

Heat penetration (HP) test data have been obtained for water in 13 sizes of metal cans and for 16 fluids with different physical properties in 211 × 400 metal cans. Data were collected until the slowest heating zone was less than 0.1 C° below the heating medium temperature. When conventional HP graphs were plotted, these natural convection heating liquids formed curves instead of straight lines. A straight line was fitted by least squares regression to the data between (T1 - T) values from 40.0 to 4.0, 10.0 to 1.0, 4.0 to 0.4, and 1.0 to 0.2 C° and the f-values determined. The results show that the f-value of fluids that heat by convection increase with heating time, indicating that the true shape of the heat penetration data on a semilogarithmic graph is a curve.