The capacity of the homogenizer is carefully calculated and fixed at a certain flow rate. As the fat content of the cream to be homogenized should be a maximum of 18 %, the ordinary cream of, say 40 %, must be "diluted" with skim milk prior to homogenization. One, with the adequate hourly volume to give the market milk the required final fat content, is routed to the homogenizer and the other, the surplus cream, is passed to the cream treatment plant. The working principle of the system, also described in Chapter 6.3, will be: After passage of the standardization device, the flow of cream is divided into two streams. The reason for choosing this system is that it can manage with a smaller homogenizer (12) and thus consume less power, while still maintaining a good homogenization effect. In this example, partial homogenization is used, so only the cream is treated. Once set, the fat content of the cream is kept constant by the control system, consisting of a density transmitter (7), a flow transmitter (8), regulating valves (9) and the control system for the standardization system. for production of butter or other types of cream. The fat content of the cream is usually set at 35 to 40% for whipping cream, but can be set at other levels, e.g. The fat content of the cream from the separator is set to the required level and is then maintained at that level, regardless of moderate variations in the fat content and in the flow rate of the incoming milk. ![]() The standardization of market milk takes place in an in-line system of the type already described in Chapter 6.2. Pasteurization unit for market milk with partial homogenization. The milk enters the unit through the balance tank (1) and is pumped to plate heat exchanger (16), where it is pre-heated before it continues to the separator (5), which produces skim milk and cream. The following assumptions apply to the plant described below:įigure 8.1 shows a typical process flow in a market milk pasteurization unit. whole milk, skim milk and standardized milk of varying fat content, as well as cream of varying fat content. The process becomes more complicated if it has to produce several types of market milk products, i.e. Here, the process line consists of a pasteurizer, a buffer tank and a filling machine. The simplest process is to pasteurize the whole milk. For instance, fat standardization (if applied) may be executed in-batch before pasteurization or in-line where the standardization system is integrated into a pasteurization unit. Processing of pasteurized market milkĭepending on legislation and regulations, the design of process lines for pasteurized market milk varies a great deal from country to country and even from dairy to dairy. Raw milk intended for intra-community trade must not contain more than 400,000 somatic cells per ml according to the EU directive. Somatic cell count is used as a criterion for ascertaining abnormal milk. These standards are shown in Table 8.1.Īnother measure of raw milk quality is the amount of somatic cells that can be tolerated in raw milk. To ensure milk quality, there are microbiological standards for intra-community trade in milk within Europe, set by the Council of the European Union (EU) to safeguard human and animal health. Gentle handling must be ensured so that the valuable constituents are not adversely affected. Processing of market milk products requires first-class raw material and correctly designed process lines in order to attain end products of the highest quality. This may occur, for example, if cattle feed contains plants of the onion family. De-aeration is practised in certain cases when the milk has a high air content, as well as when highly volatile off-flavour substances are present in the product. In many countries, the fat is routinely homogenized, while in others homogenization is omitted because a good “cream-line” is regarded as evidence of quality. In most countries, clarification, pasteurization and cooling are compulsory stages in the processing of consumer milk products. This group of products includes whole milk, skim milk, standardized milk and various types of cream.Ĭultured products are also included in this category, but as these are made with special bacteria cultures, they are dealt with separately under Chapter 11, “Fermented milk products”.Īll the building blocks described in Chapter 6 are, in principle, used in the processing of pasteurized milk products. Pasteurized milk products are liquid products made from milk and cream intended for use directly by consumers.
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