HISTORY

India has a long culture, society and tradition involving cows- they have been revered for millennia.

Verses of the Rigveda refer to the cow as Devi (goddess), identified with Aditi, mother of the gods herself.As such, the Lord Krishna called Gopal or Govinda is always seen with the cow

Dairy Animal Rearing

In India, dairy animals are reared by millions of village based smallholder milk producers/farmers. A smallholder milk producer keeps only a limited number of dairy animals (generally 2-3 animals).

The animals are generally fed on crop residues. The animals also sometimes feed on fresh grass by way of grazing in open fields.

However, dairy animals are also reared on large farms housing hundreds of animals together.

Such farms are commonly found in industrialized countries. In these farms dairy animals are fed on grains, hay, silage(conserved forage) etc. In India also, some farmers have also set-up dairy farms with larger herds compared to smallholder dairy herds.

3. Milking Operations

A dairy animal is ready to be milked when its udder is full. Usually, cows/buffaloes are milked in the early morning and again in the late afternoon.

Milking by hand

In a smallholder dairy farm where only a limited number of animals are reared, milking of animals is usually done manually by a milk producer. Such manual milking is carried out by hand by squeezing gently on the cow's teats using the thumb and forefinger. However, this way of milking needs lot of practice and takes a lot of time.

Milking with machines

Where the number of animals on a dairy farm is more, it is not feasible to milk them manually within a short period of time. In order to overcome this limitation, machines have been developed for mechanized milking of cows.Milking machines mimic the action of a young calf by creating a pulsating vacuum around the teat, which causes the milk to be released from the udder.

4. Milk Collection Operations

Once the milk is harvested, it is taken to the nearest village based collection centre by the farmer for delivery.

Farmers / milk producers from remote places travel by bicycle, cart, boat or small motorized vehicle to the nearest collection centre.Milk producers carry milk in clean utensils pour it at village level collection centres twice a day.

Testing of raw milk

At collection centres, rawmilk is tested and based on itsquality, payment is worked out. Samples of raw milk are taken from farmers prior to pouring.

The samples are then tested for various parameters like organoleptic (smell and taste), compositional (fat, and solids-not-fat) parameters etc.In case of any doubt, raw milk is also tested for presence of adulterants. Samples not found to be of good quality get rejected.

Storage of Raw Milk

Raw milk remains in good condition at normal temperatures only for a few hours after milking. Hence, raw milk collected from farmers requires immediate chilling in order to preserve its quality and avoid any spoilage due to bacterial growth.

. Many village based collection centres are individually or collectively equipped with milk chilling facilities (Bulk Milk Coolers-BMC). The BMCs are basically refrigerated storage tanks (made of stainless steel) and come in various shapes and sizes.

Milk is usually stored in these tanks at 4 degrees Celsius or colder, for no more than 48 hours. Milk inside these tanks is constantly stirred with mechanical agitators to make sure that the entire volume remains cold and the milkfat does not separate from the milk.

After every operation of milk collection and dispatch to chilling dairy processing unit, all equipment (pipelines, dump tanks / vats, BMCsneed proper cleaning before next use. This ensures that the next lot of raw milk handled at the collection centre does not get contaminated.

5.Raw Milk Transportation

Raw milk pooled at a milk collection centre is transferred to a chilling centre/dairy processing plant at regular intervals for further processing and manufacture of milk products. The mode of transfer of milk from collection centre to chilling centre/dairy processing plant depends upon the availability of milk chilling/storage facility at the collection centre.

If no chilling facility exists at the collection centre, pooled raw milk is put in milkcans (Stainless steel, aluminum cans etc.), loaded into a truck and transferred to a chilling centre/dairy processing unit immediately after each collection (morning and evening), that is, twice a day.

However, if chilling facility is available at the collection centre, then the chilled raw milk is transferred to a dairy processing unit through an insulated road milk tanker once in 1 or 2 days. The tankers have special stainless steel bodies which are insulated to keep the milk cold during transportation.

6.Processing

Raw milk received at a dairy processing unit, either in cans (unchilled) or in milk tankers (chilled), is again subjected to quality testing before acceptance. Samples of raw milk are taken from cans or tankers, as the case may be, and tested for various parameters like organoleptic (smell, taste), compositional (fat, solids-not-fat content), chemical (acidity, adulterants) and bacteriological (total bacterial count, coliform count) parameters at established frequencies.

Raw milk supplies not found to be of conforming to the specified standards get rejected. Accepted raw milk is then immediately transferred to big insulated stainless steel tanks (milk silos) and stored at low temperatures before further processing.

Further processing of milk involves steps like separation, heat processing (pasteurization etc.), homogenization etc. Processed milk may be used for manufacturing packed market milk and other dairy products like dahi, cream, butter, milk powders, ghee, ice cream etc

Typical steps in the preparation of packed market milk are as under:

a.Separation and standardization

As the term implies, separation involves spinning milk through a specific type of centrifuge (called milk separator) to separate cream from milk. After separation, cream and remaining milk may be remixed in desired proportion to obtain the specifiedminimum fat content for different types of processed milk being produced.

E.g. 6.0% fat in Full Cream Milk

4.5% in Standardized Milk

3.0% in Toned Milk

1.5% in Double Toned Milk, and

0.5% in Skim Milk

b.Homogenization

Homogenization process involves reducing the size of large fat globules of varying sizes in normally present in milk into very small (generally less than 2 microns) globules of more uniform size that are dispersed evenly throughout the milk.

Milk is homogenized using a machine called Homogenizer, which consists of a high pressure piston pump forcing milk at high speed and pressure through a narrow opening. In homogenized milk, milkfat globules remain suspended over long periods of time and do not separate as cream.

c.Heat processing

Under this step, milk is heated to render it microbiologically safe (by destruction of disease causing bacteria) and to improve its shelf life (by destroying spoilage bacteria to the extent feasible).

Some important heat processes are:

Pasteurization

Pasteurization of milk is theprocess of subjecting every particle of milk to established temperature – time combinations (e.g. heating to 63ºC and holding at such temperature continuously for at least 30 minutes or heating to at least 72ºC and holding at such temperature continuously for at least 15 seconds).This process ensures that all the disease causing bacteria and most of the spoilage bacteria in milk are killed

After pasteurization, milk is immediately cooled to 10oC or below and further maintained at temperatures around 5oC till consumption. Rapid cooling of milk after pasteurization and further holding at low temperature ensures that the surviving bacteria in milk do not get a chance to grow any further and thus helps in enhancing the shelf life of processed milk.

The term Pasteurization has been named after its inventor, Louis Pasteur of France.

Sterilization

Sterilisationof milk refer to the process of heating milk or milk product in sealed containercontinuously to at least115ºC for 15 minutes to ensure preservation at room temperature for a period not less than 30 days from the date of manufacture.This process provides almost a zero bacteria product.

Flavoured milk packed in bottles is generally sterilized through this process. After heating, milk bottles are gradually cooled to room temperature. Normallysterilized milk has a shelf life of more than 3 months at room temperature, and can be consumed directly.

Ultra High Temperature (UHT) process

Ultra High Temperature (UHT) Sterilizationof milk is the process of heating milk to at least 135ºC for a period of one second or more in a continuous flow followed by immediate cooling and then packing under aseptic condition in hermetically sealed containers to ensure preservation at room temperature for a period not less than 15 days from the date of manufacture.

While this process also provides almost a zero bacteria product, it further ensures that all the vitamins and nutritional value of the milk is retained in the final product.

7.Packaging

Packing of processed milk is generally done immediately after processing through in-line form-fill-seal machines.

Normally pasteurized milk is packed in heat-sealed sachets made of food-grade plastics and stored under refrigeration to prevent growth of surviving organisms in milk. Pasteurized milk has a shelf life of 2 days when stored and transported under refrigerated conditions.

UHT sterilized milk is packed in specialmultilayered packaging which prevents the milk from spoilage due to bacteria, sunlight and oxygen, thus ensuring freshness and purity of milk packed.

This significantly enhances the shelf life of the milk even when stored at room temperature.As the containers move through the assembly line, a date is printed on each of them to show how long the milk will stay fresh.

8.Distribution and sale

After packaging, processed milk is finally ready for dispatch to markets for purchase by customers. However, after packaging and prior to dispatch pasteurized packedmilk is stored in large cold rooms (refrigerated rooms). This milk is then dispatched for delivery to retail stores / milk parlours in either insulated or refrigerated vans in order to maintain its quality and shelf life.