Milk Pre-Processing Line



Pre-Processing processes are common in all dairy products but process steps and parameters will be changable according to the product to be producted.

Pasteurization is a common and mandatory step in the manufacture of all dairy products. Milk is pasteurized by heat treatment between 72-90 °C, depending on the type of product to be manufactured. Batch system pasteurization, pasteurization tanks (cooking) tanks are used in small capacity production plants. Electricity or steam is used for heating purposes in these tanks. In one process period, the capacity used is equal to the volume of the tank. While the milk is pasteurized, mixing is done with the help of the mixer in the tank. Thanks to its insulation there is no temperature problem outside the tank and heat saving is provided. In plants with high production capacity, continuous pasteurizer machines are used. Pasteurizer capacity is determined by the hourly amount of milk entering the machine. Pasteurizers are designed according to the number of different sections depending on the type of product. Pasteurizers, which we can describe as the heart of a plant, are coupled with other preprocessing machines all working synchronously, depending on the series. Product quality is guaranteed by automatic control units in both batch and continuous pasteurizers.
Separation of milk fat from milk composition is an important issue in milk technology. Because milk fat is an expensive material and it is used as a raw material source in butter technology and has a wide range of applications in food industry. In the pretreatment of milk, the milk fat is partially or completely separated from the milk in the composition. The reasons for this are: Obtaining low-fat or skimmed milk, providing the necessary cream for dairy products with high butter and fat content, standardization of the fat in the milk. The principle of mechanically separating milk fat from milk is that there is a significant difference between the density of skim milk and the density of milk fat. Purpose: Separate the milk into skim milk phase and cream phase. Cream separators are also used for milk standardization. Milk heated to 45-55 °C during milk pasteurization is separated into cream and skim milk phases as it passes through separators. Cream separators can be used to reduce the fat content in the output skim milk to < 0.05%. With the separators, the cream output fat content can be adjusted between 40-65%, optionally.
As is well known, milk contains some air. Freshly expressed milk contains about 6% air by volume. However, during milking, the amount of air in the milk increases continuously. The increase in the amount of air in the milk continues during processing and transportation after milking. Even though production systems are designed to be closed, air may well mix with the milk in the pumps, tanks, separators and similar machines in the production line. Air bubbles vary in size. The larger ones rise quickly to the surface and burst quickly. The smaller ones stay in the milk longer. Generally, there are three forms of air in milk: dissolved, chemically bonded and dispersed. The equilibrium between these three forms, temperature and air changes depending on the pressure. Cold milk contains more air. Air dispersed in milk may cause some problems during technological processes. In order to prevent the adverse effects caused by this air in the milk, the air must be removed. The process of air removal is called "deaeration". Devices called "deaerators" are used for this purpose. The vacuum deaeration method is used to remove the air that is dissolved and dispersed in the milk.
Since the density of milk fat is less than the density of the skimmed milk phase, fat globules accumulate on the surface of the milk over time, causing undesirable defects in the manufacture of some dairy products. For this purpose, the homogenization process is used in the production of some products. The mixture formed as a result of agitation of two non-mixing liquids is called an emulsion. When this mixture is left alone, it divides again into two phases. Milk; It is an oil-water emulsion formed by the dispersion of oil particles in the serum which forms the continuous phase. The mechanical process carried out to make the fat more stable by dividing the fat globules in the emulsion into smaller pieces in the milk is called homogenization. The main purpose of homogenization process in milk technology; It is to stop or slow down the movements of oil particles that tend to accumulate on the surface by reducing their average diameter from 3-4 μm to 0.5-1 μm. In addition, it has other purposes such as whitening the color, increasing the viscosity and improving the taste. The devices used for homogenization are called homogenizers. High pressure homogenizers are used in dairy factories. The process of breaking down the fat globules is done by passing the milk under high pressure and at a certain temperature through the valves of the homogenizer with very small gaps.
In a dairy production, a holding system is used to increase pasteurization efficiency and to provide denaturation of serum proteins. Holding process is the process of keeping milk at pasteurization temperature for a specified period of time. Holder tanks can be used as well as tube bundles for the purpose of holder operation. Generally, holder tanksa re used in buttermilk, yoghurt and cheese processes, while tube type holder systems are used in pasteurized milk production. The holder system, which is selected according to the product, Works in integration with pasteurizers.



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