Thermal treatment is widely used technology utilized to destroy microbes in food products. Nowadays, milk and milk products are handled at temperature (70 – 145°C) to make sure product safety. Most prevailing milk process is pasteurization; it enhance shelf-life upto 7-20 days. UHT and canning of milk and milk products at higher temperatures are also done. But thermal remedies implemented to exploit processing decrease nutritional value of food products due to the fact that many vitamins are heat labile. To triumph over this problem, numerous non-thermal processing technologies which includes high pressure processing (HPP) processing had been developed. Pressures amid 400 and 600 MPa inactivate microorganisms which includes food-borne pathogens. All enzymes are inactivated best at pressures of 800 MPa. HPP helps in to increase shelf-life of product, it ameliorates flavour and texture and provide desirable products.
Le Chatelier’s principle – This principle states that shift in equilibrium is due to pressure applied. According to this any phenomenon (phase transition, change in molecular configuration, Chemical reaction) take place by a decrease in volume that is enhanced by pressure. If pressure (extensive variable) changes, the equilibrium shifts in a direction that tends to reduce the change .In the corresponding intensive variable (volume). Thus, pressure shifts the system to that of the lowest volume 2].
Isostatic principle. The first attention regarding the use of high pressure is the isostatic principle, which presumes that the uniform software of stress acts similarly in all directions. A proper hydrostatic circumstance have to be unbiased of time and space. 
Significant uses in Dairy processing
HPP may be used as a renovation approach so as to lessen the milk microbial load at low temperatures. In this way, whole milk is treated at pressure of 600 MPa at 5°C for 5 min decreased the numbers of micro organism and E. coli . Moreover, there is no considerable change had been determined within quantities of vitamins, amino acids, fatty acids, easy sugars,and flavoring compounds via way of means of the software of HPP. We can do cold pasteurization by making use of 400-600 MPa for 3–15 min at 20 C, which can enhance the shelf life of milk just like that acquired via way of means of thermal pasteurization. HPP processing of raw milk (400-600 MPa) caused the reduction of pathogenic micro organism . The treatment of high-pressures (500–six hundred MPa) for reconstituted powder milk inhibited the activity of gram negative-micro organism .For spore inactivation, HPP application at pressures more than 600 MPa is mixed with thermal handling (60-90° C). But, this treatment has a drawback when processing skim milk, it turns into partially transparent form after being processed at pressures above 400 MPa this is due to breakdown of caseins.
When we use HPP on raw milk at 300-400 MPa ,it notably ameliorate curd yield by 20% of original as well as decrease both the loss of protein in whey and the volume of Whey. The consequence is because of the denaturation of beta-Lg and consequently its incorporation in the curd. This will helps in increment in production of cheese upto 7%. Ripening become also fast and intense flavour development take place when treated at 400-600MPa/5- 15 min cycle. The Cheese curd produced from milk treated by HP provides thick network of fine strands thereby having a great potential for the design of new products due to the creation of modified textures, tastes and functional Properties.
Butter and cream
When cream was processed at high pressure of 600 MPa for up to two min, its whipping properties ameliorate and decreased serum loss probable because of higher crystallization of milk fats. HPP of pasteurized cream at 450 MPa at 10 or 25°C did not affect the size of fat globules. Due to HP processing of butter or cream there is increase in the temperature (8–9°C/100 MPa). HPP have capability to fasten the maturation of cream for butter manufacturing.
HPP of 300 MPa for 15 min better the foaming properties of whey protein concentrate, which while delivered to low-fats ice cream to enhance texture of ice-cream, confirmed an improved overrun and foam balance and hardness the ice cream than ice cream delivered with untreated whey protein.HPP at 400- 500MPa for time as little as one second increase mix viscosity, resultant ice cream confirmed a sturdy growth in resistance to meltdown that enhance textural characteristics, like palatability and creaminess.
Packaging requirements for HPP
Polymeric materials, incorporation polyethylene Terephthalate, polyethylene, polypropylene, Ethylene vinyl alcohol copolymer, and their Combinations are mainly utilized as the packaging materials for HPP. To Improve the barrier properties of the polymeric films, they are occasionally coated With extremely thin layers (a few nanometers thick) of inorganic compounds such as Aluminum oxide and silicon oxide, or Metalized by the deposition (approximately 0.01 mm thick) of a thin layer of aluminum.
Advantages of HPP
It inactivate all harmful spores and bacteria
In this process there is no production of toxicity
There is no effect on colour, flavour and nutritional value
It shorten the processing time
All products will be homogeneous
It prevents use of chemical preservatives
Disadvantages of HPP
The installment cost of this technology is high
There is only few packaging available
It is less effective on activity of enzymes
There is only batch processing
Some microorganisms can survive after HPP 
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