Spray Drying Of Milk
Spray drying of milk is widely known by people in dairy industry. Without considering the high energy consumption, spray drying is the most commonly used method because this process reduces the thermal effect on the powder product. According to statistics, more than 65% of the world’s milk powder is made by spray drying. This drying process does not undergo intense heat treatment and allows the product to be stored at room temperature, which effectively maintain the biological activity of the product.
Spray drying of milk has the following advantages: First, if the drying conditions can remain unchanged, the properties of the milk powder passing through the drying tower will remain unchanged. Second, the milk drying process is continuous and easy to operate, and can be automated. However, spray drying of milk also have some common problems, one is milk powder sticks to the wall, and the other is low instant solubility of the spray dried milk powder. How to solve these two problems?
Spray drying of milk — problem 1: milk powder sticks to the wall
The adhesion of particles on the walls of spray drying towers is an important issue. It can affect the quality of spray dried milk powder or even cause a fire or explosion, and can also cause difficulty in cleaning equipment. In order to reduce this phenomenon, the sticky point test method is usually used in spray drying of milk. Many researchers use this method to control the sticking phenomenon of spray drying towers.
For spray-dried viscous substances, spray dried milk powder, for example, the sticky point curve is a semi-quantitative concept when selecting spray-drying conditions. It shows that there is no significant wall sticking phenomenon below the sticky point curve. Therefore, the information about the isothermal adsorption of materials and the temperature of the sticky point allows us to develop a series of processing operating conditions, the purpose of which is to minimize the sticking of the wall and at the same time, to reach the required equilibrium conditions of the outlet of the drying tower. For example, increasing the gas temperature at the inlet can increase the temperature of the outlet, and that of the particles at the outlet as well. However, increasing the temperature may reduce the moisture content at the outlet. As the moisture content decreases, the sticky point temperature will increase. Therefore, according to the isothermal adsorption curve, increasing the gas temperature of the inlet may shift the conditions of the outlet of the drying tower from the viscous area to the non-viscous area.
Spray drying of milk — problem 2: low instant solubility of the spray dried milk powder
The degree of heating during the drying process will affect the solubility of the spray dried milk powder. The two-stage drying method widely used in the milk powder industry has considered the sensitivity of milk protein under conditions of moderate moisture content. If the outlet temperature of the second stage drying and the temperature of the drying chamber is low, the temperature of the particles will be reduced. The moisture content of the product coming out from the drying chamber is 6% -8%, and then during the second step of drying, the protein in the dry state is much more stable than in the medium moisture content state. Therefore, choosing a higher temperature in the second stage of the drying process can make the final product’s moisture content reach 3% -4% as soon as possible, which can improve the product’s solubility and reduce negative effects.
Hawach has full types of industrial spray dryer which can be used in the drying process of milk, come and quote from us if you have any needs.