From flavoured milk to cheese, some of the best things in life are made of Milk. It is one of the most consumed foodstuff having perfect nutritional qualities. Being good source of not only protein, carbohydrates and fats but also vitamins and minerals, which helps in maintaining stronger bones, boosts immunity and provides energy. Approximately 150 million households around the globe are engaged in milk production. In most developing countries, milk is produced in the rural areas, and then transported to the dairy plants to meet requirement of urban demand. Milk has to be collected and transported from the production to processing and distribution points in cities as quickly as possible because of milk being highly perishable in nature due to abundance of nutrition, which influence positively to microbial growth.
The usual methods of milk collection and reception at dairy plant involves:
- Milk procurement through individual producers: Individual producers bring milk to plant in their own vessels, which can be of any type. This is possible for those producers who are located nearby milk collection centre.
- Milk collected through co-operative organizations: Co-operative societies form an organization, which is responsible for uninterrupted supply of milk to the dairy plant. This is beneficial to the producers as there is no middleman to share profit.
- Milk procured through contractors: Contractor supply milk by collecting milk at a cheaper rate from producers and transports the milk to the dairy. Therefore, there is less return to the milk producers, as milk contractor will keep his share in the profit.
- Milk reception from milk collection cum chilling centres: BMC (Bulk Milk Chilling) collects milk, chill them and maintain to keep them in required maintained condition until they are transported to dairy. This method is prevalent in organized sectors, and dairy operations in India.
Reception Dock (RMRD)
Raw milk reception dock also known as RMRD involves mainly two methods of milk collection.
- Tanker milk unloading: In relatively larger plants, tankers is used to receive milk. Received milk is directly unloaded in silo which are insulated to maintain the incoming milk temperature.
- Can milk unloading: In small dairy plants, where capacity is much lower in requirement, to prevent high transportation cost, milk is received usually by cans that are easy to be loaded on any form of transportation means
- Combination of both Can and tanker unloading: There are plants, which have high quantity milk requirement. In such case, mode of reception can sometimes include both tankers and cans if there is high requirement of milk.
Components & Operations
- Weighing- There are two ways of measuring the quantity of milk received at the dock either by weight or by volume. Gross weight of the tankers is recorded using weigh bridge. Weighing is done after emptying of tank as well for record. The difference between the two readings gives the net weight of milk received by the dairy. The volumetric measurement is by taking the level of milk in the tanker and translating into unit of volume. Other method is to pass the milk through a flow meter and record its reading, which is multiplied by density of milk to get weight of the milk received.
- Sampling: The first thing done at reception is to determine the quantity of incoming milk. Accurate sampling is the first pre-requisite for fair and just quality control system. Plungers and dippers are used for milk sampling. The principle of grading is platform tests which includes organoleptic tests (appearance, odour and taste), acidity sediment etc. Platform tests are the key man for the proper selection of milk. Tests involving time, laboratory facilities and special techniques are done by the quality control technician, for which a sufficiently large sample is taken.
- Unloading: The reception of milk is done at Raw Milk Reception Dock (RMRD).The RMRD dock should be of height suitable (usually 1.5 m) to receive milk from whatever mode of transport without spillage during unloading. For can unloading, the truck carrying the filled cans is brought alongside the unloading platform. The milk cans are then unloaded manually. In the absence of mechanical aids, the cans are off-loaded manually to the tipping point, where the lids/covers are removed and the milk inspected. They are then tipped manually and both cans and lids pass on to a can-washer via a ‘Drip saver’ or ‘Drain rack’. Where a higher throughput is required, the procedure is mechanized and the cans are unloaded directly from the truck onto the conveyor (power-driven or by gravity roller) and the tipping, sampling and weight recording may be completely automatic.
If a milk tanker is used, it is first properly positioned so that pipe-fitting connections can be made conveniently in the tanker bay. For tanker unloading, tanker is connected to milk transfer pipeline via flexible hose. Hose selection is an important parameter as it should be non-reactive to milk during transfer.
- Milk Chilling: Immediately after receiving the milk, it is cooled to temperature of about 4°C or 5° C to supress the microbial load using surface coolers, Plate Cooler or Internal Tabular Cooler and stored cool till used in raw milk silo.
- Milk Storage: Raw untreated cooled milk is stored in large vertical storage tanks (known as milk silo tanks) which holds the milk until it is further processed. Silos can be located either indoor or outdoor of the plant. The storage tanks must be designed for ease in sanitation, preferably by the circulation-cleaning method. In addition, the tanks should be insulated or refrigerated, so that they can maintain the required temperature throughout the holding period. Silos are equipped with side-mounted propeller agitator for preventing layering of cream at top of the tank.
- Booster pump: – It facilitates transfer of milk to silo and is check temperature of milk passing through PHE by regulating the flow.
- Disk Filter: – Incoming milk is filtered before stored in silos, as there can be impurities and contamination.
Fact of India being leading producer of milk puts lot of pressure on processing of maximum amount of produced milk. Milk being rich in fat and protein, makes it important to process milk immediately or else to be stored in required condition until being processed. Milk is prone to several post-secretion changes, some natural and some man-made. Naturally, milk being a product of biological origin, is extremely vulnerable to attack of microbes. It is also a good vehicle for additives and adulterants without any apparent changes in its appearance thus can be easily adulterated. Thus, Milk Reception is the critical stage in deciding the quality of dairy products as it depends upon quality of raw milk used in their manufacture, processing and handling.
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