Presently, Ultra High Temperature (UHT) milk has seen huge success in large areas of Europe. It is said that 7 out of 10 Europeans drink UHT milk regularly. In fact, in a hot country such as Spain, 96% of the milk consumption is credited to UHT milk due to high costs of refrigerated transportation and “inefficient” cooling cabinets. In 2008, the British government proposed a 90% UHT milk production target to be achieved by the year 2020. The government strongly believed that this target would help in significantly cutting down the need for refrigeration, and thus benefit the environment by reducing green-house emissions.

The Indian dairy industry has experienced a number of developmental stages such as farmers taking the cows to the city and milking at the doorsteps, followed by established milk processing plants and milk sold by coin operated vending machines, followed by current method whereby milk is pasteurised and packed into plastic pouch.



 The technology applied to milk processing and packaging plays a vital role in economy of a dairy plant. The dairy must operate profitably in order to serve its customers, in the best possible way.


Shortcomings related to pasteurised milk

Although pasteurisation offers great advantages in comparison to raw milk distribution, it has some major shortcomings such as:

  • Short shelf-life
  • The necessity of a cold chain during delivery and marketing
  • Inflexibility in the production and delivery schedules
  • Excess product returns

Because of these shortcomings, the consumption of pasteurised milk has been confined to big cities, metros and towns near the processing plants where the main dairies can provide refrigeration easily. To maintain the good quality of pasteurised milk, the milk needs to be kept at a temperature below 5oC, all the time during collection, storing, and distribution. But in practice, this is often very difficult to achieve.


UHT milk

Today, UHT and aseptic packaging is fast gaining popularity all over the country. In the UHT process, milk temperature is raised quickly up to 142oC for 2 seconds.

The sterilisers are readily available to be equipped with an inline recombining/reconstituting system. This makes it possible to process milk powder into normal liquid milk and also to produce other liquid milk based products such as flavoured milks, juice-yoghurt drinks, soft-ice cream mixes, milk shakes, just to mention a few.

 Main advantages of UHT milk are:

  • Easier production planning.
  • The long-keeping properties of UHT products mean that production can be concentrated to long runs of one product at a time
  • Better utilisation of equipment. The same UHT plant can be operated for a variety of products such as milk, cream, fruit juices, etc., thus can have broader production range
  • Simplified handling of finished products.
  • Elimination of the need for cold storage reduces the demand for both the refrigeration plant and the heavy insulation of storage areas, in the dairy transportation, selling outlets and at homes.
  • Possibility to gain wider geographical markets.
  • Sales through new outlets.
  • With UHT, there is less cost and risk involved in introducing new product lines, flavour varieties, etc. because it is easy to match production to demand from the market.
  • Need fewer distribution vehicles without insulation/refrigeration
  • Simplification of delivery schedules. There is no need to cover the whole area every day; deliveries can be made once or twice in two weeks to different districts in rotation.
  • Elimination of the return of unsold products.

Even slightly cooked flavour the UHT milk has is liked by many consumers.

To sum up, UHT makes the producer’s operation more competitive by enabling dairy to sell more products to more consumers at a lower unit cost for distribution.

UHT milk production has grown from 600 million litres in 2006 to 1 billion litres in 2013. Taste, convenience and distribution will no doubt contribute to the faster growth of UHT milk. As more people become aware of this technology and its benefits and know where to find the product, UHT milk will grow further.

It is likely that for an existing dairy, the UHT milk segment can be just an extension of the pasteurised milk processing. Since the entire infrastructure for the dairy plant exists, the UHT equipment would be simply an extension. One needs to add a steriliser and aseptic filling machine — as per requirement and upgrade the existing facility’s utility section.

The UHT treated milk when packed aseptically gives a longer shelf life at ambient temperature. To achieve the longer shelf life, the product is treated at ultra high temperature, that is it is heated at 140-142ºC for a brief period and then rapidly cooled to room temperature. This results in eliminating all the microorganisms and harmful bacteria for human consumption without loosing the nutritional value of the product and making it safe. In aseptic pouch packing technology, the film and the product filling path are sterilised using hydrogen peroxide, in a very innovative way, to sterilize the co-extruded, multi layered packaging film with ethyl vinyl alcohol (EVOH) barrier. The triple sterilisation principle employed in the design of the machine ensures that film is thoroughly washed and sterilised before it reaches the filling point. The filling is done in sterile atmosphere to avoid re-contamination, thus aseptically packing the product.

The products that have been processed and packed with UHT system include milk, flavoured milk drinks, yoghurt-based drinks, fruit juices, soft ice mix, milk shakes mix and nutrient solutions



The aseptic processing system for UHT treatment of plain milk, flavoured milk and any other product ensures that they can be stored and distributed under ambient temperature. A UHT processing system uses indirect steam heating type UHT steriliser with straight tube in tube type tubular hear exchanger to sterilize the products at capacity ranging from minimum 2,500 litres per hour (LPH) to maximum of 6,300 LPH including 5% recycling. The aseptic pouch packaging system is integral and synchronised with the steriliser having a capacity to pack maximum 10,800 packs per hour. The filling machine is double head type allowing the possibility of packing two different pack sizes at a time with each head having a capacity to pack 3600 packs/hour. The machine is able to fill varying pack sizes from 180 ml to 1000 ml packs.


Principle of operation

The plant is fully automated for production steps ascertaining the sterility of the product, CIP steps, homogenisation of the product etc. The system should start with circulation of hot water with a pressure for the prescribed time and temperature. Immediately after pre-sterilisation the system is aseptically cooled down step by step to the production temperature.

The system is incorporated with different straight tube bundles viz. regeneration, heating, cooling holding etc. The plant is having the facility to perform automated CIP after and in between production.

 When processing, the milk is pumped from the balance tank through a number of regeneration section to preheat the milk. During this process, the milk is preheated to around 85oC, held for a few minutes in a holder tank and then homogenised. The milk is then further preheated to higher temperature in another regeneration section. It is then heated to the pre-set temperature (140-142oC) in a heating section by high pressure steam. After a holding period of 2 seconds, the milk is cooled in stages in the down-flow regeneration sections to the filling temperature before it goes to the aseptic packaging machine. The capacities of the steriliser and the packaging machines are synchronised together thus eliminating the need of complicated aseptic intermediate tanks.

A complete UHT assembly consists mainly of:

  • UHT steriliser
  • Homogeniser
  • Aseptic packaging machine
  • CIP washing equipment


UHT steriliser

The steriliser is comprised of required amount of straight-pipe heat exchanger cartridges with the amount of the cartridges determined by the desired sterilising capacity. The control of the steriliser is automatic synchronised with the filling machine. The control and alarm system is equipped with temperature recorder and temperature control unit and with automatic recycle valve in case the sterilising temperature decreases below the set temperature.

The daily sterilising of equipment is performed by circulating water through the pipage. During the circulation the temperature of the water is raised up to +140ºC and after which the plant will be taken for production.



Homogeniser is equipped with remote-controlled speed adjustment, which is situated in the central control panel of the steriliser. All parts in contact with the liquid are of stainless steel. The machine is enclosed in a cabinet of polished stainless steel. The homogeniser is equipped with forced lubrication system.


Aseptic pouch filling machine

Pouch filling machine is a fully automatic packaging machine, having single, double or triple filling heads, for liquid products producing pouch packages aseptically and automatically. The film from the film roll travels over the rollers through the hydrogen peroxide bath to the ultra violet (UV) cabinet. The aseptic condition is achieved by sterilising the film with UV radiation, immersing the film in hydrogen peroxide bath and subsequently drying it in hot air. Continuous positive sterile air pressure is maintained inside the film and UV cabinet. In the sterilising cabinet both sides of the film are treated with effective UV-radiation. After sterilising, the film is folded by means of a triangular turning device so that the surfaces to be sealed are pressed against each other. The film indexing can take place using servomotor-controlled pulleys. The metering and sealing take place in the fill and form cabinet.

The sterile air is generated using a separate sterile air generating system and directed into the filling and sealing cabinets of the machine generating positive pressure inside and keeping the machine sterile and maintaining the aseptic condition. The metering device parts remaining in the pouch blank are sterilised before starting the run. The interior sterilising of the metering device is carried out before starting the packaging with super-heated water (+120ºC). The metering device is a piston/cylinder metering pump functioning with the pressure of the product to be portioned. The liquid flow is in a hermetically closed system constructed especially to meet the requirements of sterile packaging. Both the horizontal and vertical sealing devices are of continuously heated type. Step-less adjustable temperature control is equipped with sealing temperature indication.

In order to keep the air of packaging room fresh the machine is equipped with an exhaust air outlet with duct connector for removal of any possible fumes generated in connection of film sterilising process.

 The aseptic pouch filling machine comprises the following accessories:

Coding unit: A hot foil-stamping device stamps minimum 9+9 digits on the film to indicate the packaging date, the last selling date or other information.

 Film web controller: A sensing device placed at the film web stops the machine as the end of the film has passed by the sensor. The new film roll can be attached by sealing the film ends together.

Pouch counter: An indicator in the drive panel of the machine is provided. The counter measures the number of portions.

The blower sucks in the dry ambient air via the intake line, through the Air Pre-Filters. The intake air is then “Compressed” (about 0,1 bar overpressure) and led through the Sterile Air Filters and Forward into the packing machine(s). The sterile air filters retain micro organisms and all kind of bacteria and/or other contaminants. The sterile air filters are sterilised before starting a production run by means of filtered steam (4 bar or +140ºC) led in the unit via the Steam Line. During sterilisation process the airline downstream of the blower is automatically closed to protect the blower from the steam. After sterilisation of the Sterile Air Filter the condensate is drained out the condensate valves.

Aseptic pouch filling machines are designed to be able to produce any size pouches between 180-1100 ml. Also, if necessary, each head can be adjusted to operate on different pouch size. This feature ensures more flexibility for the dairy to respond to the market demands.

The machine has the following features:

  • No need of refrigeration
  • Pre-cut device for easy opening
  • Standipak unit to convert pillow pouches to stand-up pouches
  • Variety of different options for downstream equipment
  • UHT product is suitable for future requirement stipulated by supermarket chains.


Balancing equipment

A balancing equipment is used in the system, which functions as a balancing unit between the steriliser and the packaging machine. This should replace aseptic intermediate tanks. In case one of the filling head is momentarily stopped the steriliser capacity can be adjusted to suit the remaining packaging capacity. The quantity of the recycled products is approx 5%.

Balancing equipment consists of aseptic product valve, changeover valve and pressure regulating valve connected to the product line for sterilised milk and to the return product line.


Specifications for packaging material

High quality pre-sterilised, flexible packaging materials processed from virgin linear low density polyethylene (LLDPE)/low density polyethylene (LDPE) raw material suitable for forming, filling and sealing in aseptic pouch filling machines with the following minimum technical data are specified:

  • Number of film layers                                   3 to 5
  • Thickness                                                         120-180 micron
  • Width                                                                260-320 mm
  • Structure                                                          Grey/black/white
  • Raw material                                                   LLDPE, LDPE
  • Printing                                                             1-6 colours

Following packaging films are recommended for different shelf life requirements:

LDPE/LLDPE film is an economical solution for short shelf life (10-30 days). Polyamide (PA)/LDPE + LLDPE film for medium long shelf life (1-3 months) Polyethylene terephthalate (PET)/A1/PA/LDPE + LLDPE for long shelf life (3-12 months). The barrier layer can also be of EVOH or polyvinylidene chloride (PVDC). Table 1 provides the theoretical yields of pouches of different sizes from the packaging film.


Table 1: Theoretical yield per one kilogram of film

Pouch size


Weight of pouch


Yield per kilogram


200 3.0 333
250 3.3 300
500 4.5 220
1000 7.0 143


CIP washing equipment

The CIP equipment is designed for automatic circulation and washing of filling machines and steriliser. There is washing programme for intermediate and final washing. Only the CIP of the steriliser is carried out intermediately after the heat exchangers have become impure by operating for a long time. After the intermediate washing, the processing can be continued normally. The final washing is performed both for the steriliser and the filling machines after the processing has ended. Considering the overall advantages of UHT processing, it can be safely assumed that there is good scope for this technology in India as seen in developed countries.