Milk is necessary for both infants and children and is a most important food for adults. In fact, it is essential for the welfare of the human race.
Since it is perishable and an ideal product for bacterial growth, it must be carefully handled, both during production and while processing.
Raw milk available for human consumption must be low in bacterial count, free from disease germs, and visible dirt, and have an acceptable flavor.
Once the milk has been received at the milk processing center, or dairy plant, it should be immediately strained, cooled, and processed so as to prevent any further bacterial growth.
Various operations performed at the milk processing center include pasteurization, cooling, cream separating, butter churning, ice cream freezing, bottle filling and capping, bottle washing, can washing, etc.
Essential Milk Handling Equipment in Dairy Operations
Milk handling starts from milking operation to milk packaging and involves different equipment along the processing line.
The equipment used depends on the quantity of milk to handle and can be small- or large-scale processing equipment.
Milk Room Sanitation Standards
Sanitation is the primary consideration in the handling of milk, whether it is from one or two cows belonging to a smallholder or from a commercial herd supplying milk for the city.
In either case, an adequate supply of potable water is essential for cleaning the milking equipment immediately after use. Hot water (85 °C), mixed with a chemical detergent, is required for effective cleaning, and cold water is used for rinsing.
Milk should be handled in a separate area that is easy to clean and is free of insects, birds, rodents, and dust. A smallholder producing milk only for the household may be able to process, curdle, or consume the milk within a short time so that cooling is not necessary.
Selling milk to the public requires higher standards of sanitation and more elaborate facilities. Whether the cows are hand- or machine-milked, a separate milk room adjacent to the milking stalls or milking parlor is needed.
This room should be well-ventilated and designed with a concrete floor with a slope of 20 mm/m to a drain and masonry walls with a smooth, water-resistant surface that can be easily and thoroughly cleaned.
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Milking Machines for Dairy Production
Milking machine is the first equipment used in milk handling. The machine is used for collecting the milk from animals. The machine gives good quality and operates with a uniform vacuum of 275-350 mm of mercury, provides a massaging effect on the teats, and is easy to clean.
The milking machine simulates nursing by the calf. Two vacuum lines lead to the teat cups. A pulsator supplies an intermittent vacuum to one line at the rate of 45-60 pulses per minute. The line, connected to the shell of the teat cup, causes the teat inflation (rubber liner) to alternately expand and collapse.
This massaging action promotes normal blood circulation in the teat. The second line maintains a continuous vacuum on the teat and carries the milk either to a stainless steel bucket or through a pipeline directly to the milk cooler.
This type of system is often chosen for the small- and medium-size herd. The labor of carrying the milk to the cooler has been reduced through the use of a pump transfer system.
This consists of a 30-liter receiving tank, including a built-in filter, mounted on wheels so that it can be moved around the stable. It is connected to the cooler with a plastic hose, and the milk is drawn to the cooler by vacuum from the milker pump.
The hose is reeled in or out as necessary as the cart is moved around the stable. In a large-scale system, pipeline milking systems are usually installed in milking parlors, where the operator stands below the level of the cows.
Although they are expensive, they reduce the back-breaking tasks and are usually designed to be cleaned in place.
Milk Cooling Systems
Coolers are equipment used for chilling the milk to about 4°C. This is done to check the multiplication of bacteria and to preserve the quality of milk until it is subjected to pasteurization process.
Pasteurization Equipment
Pasteurizers are machines used for heating the milk to at least 61°C and holding it at that temperature for 30 minutes, or heating to at least 70°C and holding it at that temperature for at least 15 seconds.
This process destroys most of the bacteria in milk and particularly all disease-producing organisms. It also improves the quality and taste of the milk. There are two basic types of pasteurizers: batch type and high-temperature short-time type.
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Milk Transport Vessels
These are equipment used for transporting and storing milk from the farm to collection centers or milk processing plants. The equipment is categorized into two: milk cans and tanks.
1. Milk Cans: These equipment are used to store milk for a short time and transport it over short distances. The material is not usually insulated, therefore may lead to poor milk quality.
Since the cans are not insulated, the transport to the factory must be efficient enough to enable milk to reach the factory in acceptable condition.
2. Milk Tanks: Tanks are usually made in rectangular and horizontal or circular and vertical shapes. The shell of these tanks is made from stainless steel and surrounded by jacketed space for circulation of refrigerated water or coolant.
The tank is insulated with non-toxic material and is used to transport milk in bulk over long distances.
Refrigeration and Cold Storage for Milk Products
Refrigeration systems are used to preserve the milk; the system works on the same principle as a home refrigerator. A cold-generating fluid in liquid form is distended into an evaporator and produces cold.
The heat created by the compression-condensation system is evacuated by means of a ventilator.
The cooling level is regulated at the beginning by the mass of milk and then by a thermostat that stops the compressor when the milk has reached the desired temperature.
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