(1) Conventional heat sterilization
1. Heat transfer mode Indirect heat exchange is carried out using a heat exchanger whose rate depends on the heat transfer conditions of conduction, convection or radiation.
In the case of differential wall heat transfer, heat is first transferred from the heating medium (such as water vapor) to the liquid in the food material through the partition wall, and then transferred to the solid particles by convection and conduction between the liquid and the solid particles, and finally the conduction inside the solid particles. Heat, so that all materials reach the required sterilization temperature.
The heat transfer rate is slow and the heating is unbalanced.
2, heating effect In order to achieve the sterilization temperature inside the solid particles, the surrounding liquid part must be overheated, which will inevitably lead to the soft and rotten texture of the grain-containing food after sterilization, affecting the product quality.
(two) electrothermal sterilization
1. Heat transfer method The fluid is applied simultaneously with the particles. If the conductive properties of the two are similar, the two heats up at the same time and the heating degree is fairly uniform.
The pellet heating rate is much higher than conventional methods.
2, heating effect The purpose of the product does not experience a large temperature gradient when heated and the liquid and particles are heated at the same time, so the processing time is short, the product quality is high, the product can maintain the intact particle shape after high temperature treatment.
The heated surface does not burn, the product is not allowed to stir during heating, and the liquid carrier does not need to be excessively heated to heat the particles and the particles are evenly heated.