Steam injection

Direct exchangers are based on mixing of heating steam with the liquid food product resulting in very fast heat transfer rate. Steam injection and steam infusion are each used to intimately combine the product with potable steam.

In steam injection, the steam is injected into the fluid food through small hole. A typical example is the production of UHT milk by direct steam injection.

Milk is pre-heated to 75 ° C and then brought into contact with saturated steam, resulting in almost instantaneous heating of the UHT temperature. The milk plus the injected water come in the expansion vacuum vessel, where the added water of the steam injection is removed through condensation in the following condenser.

Control of the pressure in this system is needed for two reasons. First, this is to ensure that the correct amount of water is driven off, and second, that any undesirable volatile odors that may have developed during the injection process are removed.

The advantages of direct steam injection are their quick and accurate temperature control (within less than 1 ° C), the restricted pressure drop under normal flow rates (less than 0.14 bar) and their relatively low noise during operation (less than 80 dB).
Steam injection