MODERN METHODS FOR PRODUCING MILK POWDERS

ABSTRACT

In this work, existing technologies for the production of milk powder intended for processing raw materials on an industrial scale were analyzed. Brief information reflecting the main content of the article, as well as data on the mechanism of operation of the spray installation, was provided.

АННОТАЦИЯ

В данной работе были проанализированы существующие технологии производства сухого молока, предназначенные для переработки сырья в промышленных масштабах. Также были приведены краткая информация, отражающая основное содержание статьи и данные о механизме работы распылительной установки.

Keywords: milk powder, spray drying, chemical content, dairy materials.

Ключевые слова: сухое молоко, распылительная сушка, химический состав, молочные продукты.

The dairy sector of the agro-industrial complex, which is part of the food industry, is a socially significant sector of the economy. Today, within the framework of modern biotechnology research, there is a tendency to study functional foods.

The study of modern methods for producing milk powder opens new prospects for the development of preservation technology. Since raw milk has a short shelf life and therefore low transportability, it must be preserved. One of the most effective methods is drying milk raw materials, which allows you to obtain dry powdery products. In its physical essence, drying is a complex diffusion process, the speed of which is determined by the rate of diffusion of moisture from the depths of the material being dried into the environment.

Powdered milk is used to produce ice cream, whole milk products, processed cheeses, and mixtures for functional baby and sports nutrition. Functional foods and beverages are the fastest growing segment of the food industry in the world today. The dynamics of the industrial sector also affects the Uzbek milk powder and cream market.

Currently, existing technologies for the production of milk powder are designed for processing raw materials on an industrial scale. However, the main suppliers of dairy raw materials to factories are farms, which are often located remotely from markets and face the problem of transportability and short-term storage of fresh milk. To solve this problem, it is necessary to develop a technology for drying milk in small-scale production, which will allow drying excess raw materials and obtaining whole milk powder with a long shelf life directly at the production site.

Milk is a multicomponent bioorganic heterogeneous system that has the properties of an emulsion, as well as a true and at the same time colloidal solution. Milk contains the following main components: water - 87.5%, dry matter - 12.5%, protein - 3.3%, fat - 3.5%, milk sugar - 4.7% and 1% minerals.

The chemical composition of milk and its taste depend on the type of farm animals, the conditions of their feeding and housing, and several other factors. The fat content in milk changes to a greater extent, and the content of milk sugar and minerals changes to a lesser extent.

Also, the chemical composition of milk changes during lactation, milking time and a number of other factors affecting the physiological state of animals, and in most cases has a functional nature. The main influence on the percentage of fats, proteins and vitamins in milk is exerted by the quality and completeness of feeding and the conditions of keeping animals [1, p. 7].

To increase the shelf life of food products, a method such as desiccation, or, in other words, drying, is used. This is since the removal of moisture eliminates the possibility of microbiological and biochemical processes occurring [2, p. 18]. For example, the vital activity of bacteria requires at least 30% moisture, and for the development of mold - at least 15%. In the dried product, all metabolic processes of microorganisms are disrupted, as the concentration of dry residue increases. Drying also facilitates packaging, transportation and storage of products, reduces the weight and volume of the product.

Milk as a product has a short shelf life and, therefore, low transportability; to increase its shelf life it must be preserved. The main and most effective method of preservation is drying milk, which leads to the production of dry powdery products. Drying is a mass transfer process consisting of the removal of water or other solvent by evaporation from a solid, suspension or liquid [3, p. 127].

Powdered milk is a fine powder consisting of single and agglomerated particles and is a concentrate of ordinary cow's milk [4, p. 74].

The quality of milk powder is greatly influenced by the method of its production [5, p. 25], in other words, the heat treatment during its production, in particular, the equipment used and the drying technology itself. Proper compliance with the production conditions and technological regulations allows you to preserve almost all the beneficial properties and taste of the dry milk product. At the same time, the resulting dry milk concentrate is highly compact during transportation and has an increased shelf life under different temperature conditions.

Currently, the food and dairy industry uses the following basic technological methods for removing moisture from dairy products:

• Spray drying is a method of producing milk powder by spraying the milk powder into a hot drying chamber.
• Contact (conductive) drying is a process in which heat is transferred to the product being dried directly through the hot surface of a heated element.
• Evaporation is the concentration of milk or dairy products in multi-effect vacuum evaporation units.
• Freeze drying – removal of up to 80% of water from milk by freezing (sublimation) for 5–8 hours at temperatures below – 20°C.

In the heated spray drying chamber, the processed raw materials are sprayed through a nozzle and converted into a dry product. Before spray drying, milk goes through preparatory stages: pasteurization, normalization to the desired fat content, thickening, homogenization of milk. In most cases, pasteurization of milk is carried out at a temperature of 72–75°C without holding. Next, the milk is condensed in vacuum evaporators to a solids concentration of 45–50%. After this, the condensed milk must be homogenized, since condensation causes a partial increase in the size of the fat globules, which may lead to the formation of free fat in the milk powder, which easily oxidizes in air and leads to the formation of the taste of animal fat in the milk powder. The homogenization process is carried out at a temperature of 50–55°C and a pressure of 10–15 MPa.

The spray installation works as follows: air for drying is taken from the atmosphere by a blower fan, after passing through the cleaning system, it is heated and enters the air distributor located on the top of the device and is supplied to the heated chamber. Under high pressure or through pneumatic nozzles, the prepared milk enters a chamber in which atomization is carried out by a jet of heated air. The moisture contained in the sprayed droplets evaporates upon contact with hot air, and the air cools. Most of the dried raw material settles to the bottom of the chamber and is fed into the pneumatic transport and cooling system. However, small-diameter particles are carried away by air; to settle them, air must be passed through cyclones.

The main advantages of spray drying installations are the following technological advantages:

1) high speed of the drying process when obtaining dry products;

2) contact of the original product with the walls of the dryer is eliminated and the risk of corrosion of the drying chamber material is reduced;

3) spray drying on an industrial scale is suitable for all types of dairy and vegetable raw materials.

When using two- or three-stage drying technology, the resulting dry product is completely ready for use, does not require additional grinding, has a uniform structure and a high solubility index. In most cases, the product is immediately ready for packaging.

The disadvantages include:

• large dimensions of drying units, requiring large areas of premises for their placement;
• high costs of thermal and electrical energy when obtaining dry products;
• partial loss of dry product during single-stage drying due to its entrainment by the air flow leaving the drying chamber.

References:

1. Colella, A. P., Prakash, A., & Miklavcic, J. J. (2023). Homogenization and thermal processing reduce the concentration of extracellular vesicles in bovine milk. Food Science & Nutrition, 00, 1–10. https://doi.org/10.1002/fsn3.3749     
2. Tetra Pak. (1995). Dairy Processing Handbook. Tetra Pak Processing Systems, G3.
3. Dmitrichenko, M.I. Examination of the quality and detection of falsification of food products: textbook/M.I. Dmitrichenko. – St. Petersburg: Peter. – 2003. -160 p.
4. Zakharova, L.A. Technology of milk and dairy products. functional products: textbook / L.A. Zakharova, I.A. Mazeeva. - Electron. Dan. – Kemerovo: KemSU, 2014. – 107 p. - Access mode: https://e.lanbook.com/book/60194    
5. Zolotin, A.Yu. Classification of fermented milk products for baby food/A.Yu. Zolotin, N.P. Androsova // Dairy industry. – 2001. – No. 12. – P. 23-25.