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COOLING OF MILK

Milk is the normal mammary secretion derived from complete milking of healthy milch animals. It is an almost complete food. The new born infant is not equipped to ingest and assimilate nutrients from any food source other than milk. Milk is indispensable food item of adults and convalescents. Milk contains on average 87 per cent water, 3.9 per cent fat, 4.9 per cent lactose, 3.5 per cent protein and 0.7 per cent minerals, vitamins. Milk of ruminants like cow, buffalo and goat is ideally suited for human consumption and meet the basic dietary requirement of human being.

But milk is perishable food item. It is nutritive to both animals and microorganisms. Consequently, shelf life of milk is too short and is about 2-3 days after collection of raw milk from udder. Milk is produced constantly at the farmers’ facilities where the cows are milked. The milk is then transported long distance on tank trucks and delivered to the different dairy and milk plants. The milk is then sent to urban centres for distribution as liquid milk or processed cheese, butter, milk powder and many products. So there is a huge time gap between milk collection and processing. Not only that, these milk and dairy products may not be consumed for a week or months after leaves the farm. So there is a large chance of contamination of milk by microorganisms or unclean utensils kept milk or wrong handling.

Streptococcus sp. and Faecal coliform has a large impact on spoilage point of view. The milk leaving the farm must be of good nutritional and bacteriological quality and be uncontaminated by soil and chemical pollutant. We have to assure the consumers that the milk and dairy products maintain hygiene quality and compliance with some regulations are key to guaranteeing the quality. In the industrial point of view, it is required to increase the shelf life up to 30days.

Cooling is the process of bringing the temperature of milk below ambient temperature using a cooling medium. After the reception of milk, immediate cooling can retard the growth of Thermoduric and Mesophillic microorganisms. Mesophillic microorganisms can grow at 20- 40°C and it brings serious diseases to the consumer. Cooling reduces the metabolic activity of microorganisms by reducing the activity of the enzymes necessary for metabolism. Milk must be cooled below 4°C after collection.

Rapid Milk Chiller is a modular milk chilling system that instantly cools milk from 35o to

4o C without a diesel generator. The system can chill 1000 litres of milk per day, even if there is no power during the milk collection by using only 4 hours of intermittent grid power between each milking shift. Most places in India, especially the villages in the country are suffering from acute power shortages. On top of that, natural calamities add up to their misery. Some places do not have electricity for 24 hours a day and at times for 3-4 days a week due to power failure. This makes it difficult to run any business. By eliminating a Diesel Generator set, Milk Chiller provides the most cost effective way of collecting top quality chilled milk from village milk collection centers where grid power is erratic.

Sorin Grama was running a market study in rural India, along with his team, when he was introduced to this problem by Bangalore Dairy in 2007. This led to the creation of a magical product-‘Rapid Milk Chiller’. While there is a similar product called Bulk Milk Chiller (BMC) already available in the market for a long time but the real challenge is that it runs on diesel generator. It makes it highly expensive both in capital and operating cost, specially in

Packaging Of Dairy Products PDF Book

India. This is why many BMCs are not available at the village levels. Rapid Milk Chiller has a thermal battery backup system which solves the unreliable electricity problem. This battery is not an electrical battery; however, it is thermal and stores thermal energy. To be specific, it stores energy in the form of ice, something that is ideal for refrigeration applications because energy is required for the transition of a substance from one state to the other. The thermal battery is charged using the electricity that is available (at least 6 hours per day is always available in villages). The charging is done by a refrigeration compressor that cools a fluid and makes ice. Once the battery is charged, the ice formed is available to chill the milk whenever needed. Milk needs to be chilled at two specific times a day (early morning and early evening). The battery is not used when electricity is available, however, if there is no electricity then the battery seamlessly turns on and continues chilling the milk. Besides the battery, the Rapid Milk Chiller system includes components such as a rapid heat exchanger for rapidly cooling milk and a smart control system for monitoring and controlling the entire system.

Cooling of Milk

Rapid Milk Chiller Components

  1. Thermal storage system
  2. Chiller Unit
  3. Milk Heat Exchanger

India is the largest milk producer since last few decades. But lack of proper industrialization and improved equipment, milk and dairy products can not able to export to different countries. So, Rapid Milk Chiller machine is very important machine which can prevent spoilage of milk and increase shelf life of milk and dairy products. It is a boon to rural dairy system. This machine must be used to every reception unit.

Reference:

  1. Sankara Reddy, A.K.Puniya, INTRODUCTORY DAIRY MICROBIOLOGY
  2. S.Sarma, CHEMISTRY OF MILK
  3. R.K.RAJPUT, A textbook of Heat and Mass Transfer
  4. electronicsforu.com
  5. coolectrica.com/

 

Article Written By

RAJARSHI SWARNAKAR

STUDYING DAIRY TECHNOLOGY UNDER WBUAFS

EMAIL: swarnakarrajarshi11@gmail.com

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