High-pressure processing uses high pressure, rather than heat, to preserve foods by inactivating harmful pathogens. Pressurizing foods to levels above 200 MPa uniformly inactivates microorganisms like bacteria and extends shelf life with little effect on taste, texture or nutrition. The process involves sealing foods in flexible packages and submerging them in water inside a high-pressure vessel. As pressure is applied, microorganisms are inactivated due to damage to cell membranes and proteins. This non-thermal method allows for minimal quality loss compared to heating and improves food safety.

1. HIGH PRESSURE
PRESERVATION
.

2. INTRODUCTION
 High-pressure processing (HPP) is a “nonthermal” food preservation technique
that inactivates harmful pathogens and vegetative spoilage microorganisms by
using pressure rather than heat to effect pasteurization.
 Allowing most foods to be preserved with minimal effects on taste, texture,
appearance, or nutritional value.
 Pressure treatment can be used to process both liquid and high-moisture-
content solid foods.( Aw=0.95)
 For example, a grape can be easily crushed if pressure is applied to it by placing it
between two fingers and squeezing along one axis. In contrast, if the grape is
exposed to a uniform pressure by submerging it in water inside a sealed flexible
bottle and squeezing, the grape retains its shape no matter how hard the
 bottle is squeezed. In this case, the pressure transmitted from the bottle wall
through the water is applied uniformly around the fruit.
 Porous system will collapse ( eg strawberries are crushed by HPP)
 U.S., Canada, and Mexico, Spain, Italy, Portugal, France, UK, and Germany,
Australia, and Asia (Japan, China, and S. Korea) lead the commercialization of
high pressure technology.
 Cost is 0.5-2.5 Million $ ( equipment) and HPP treatment costs are quoted as
ranging from 4–10 cents/lb ( equal to that of thermal processing)

3. PRINCIPLE.
• Le Chatelier’s principle. Any phenomenon (phase transition,
change in molecular Configuration, chemical reaction) accompanied
by a decrease in volume is enhanced by pressure. Accordingly,
pressure shifts the system to that of lowest volume.
Isostatic principle: The principle of isostatic processing
is presented in . The food products are compressed by
uniform pressure from every direction and then returned to
their original shape when the pressure is released. The
products are compressed independently of the product size and
geometry because transmission of pressure to the core is not
mass/time dependant thus the process is minimized
If a food product contains sufficient moisture, pressure will
not damage the product at the macroscopic levels as long as the
pressure is applied uniformly in all directions

4. HIGH PRESSURE EQUIPMENT
 COMPONENTS
 1) Pressure vessel
 2) High pressure intensifier pump
 3) a system for controlling and monitoring the pressure
 4) a product-handling system for transferring product to and from the pressure vessel
 5) Compressing medium like water, glycol solutions,silicone oil, sodium benzoate
solutions, ethanol solutions, inert gases .

5. A typical HPP process uses food products packaged in a high-barrier, flexible
pouch or a plastic container. The packages are loaded into the high-pressure
chamber
The vessel is sealed and the vessel is filled with a pressure transmitting fluid
(normally water).
Pressurized by the use of a high-pressure pump, which injects additional quantities of
fluid. The packages of food, surrounded by the pressure-transmitting fluid,
are subjected to the same pressure as exists in the vessel itself.
After holding the product for the desired time at the target pressure, the vessel is
decompressed by releasing the pressure-transmitting fluid.
Approximately 5–6 cycles/hr are possible, allowing time for compression, holding,
decompression, loading, and unloading.
After pressure treatment, the processed product is removed from the vessel and
stored/distributed in a conventional manner.

6. Prodcuts Pressure Shelf life Inhibits Advantage
( Mpa) ( at 4 deg ( pathogens
( 1-5mins) C) and spoilage )
Meat and meat 500-600 More than Listeria , Effective in eliminating
products 90 days Salmonella , pathogenic micro-
( sliced, ( 45 days E.coli, moulds , organisms.
marinated,whol without yeast etc.
e) 31% HPP)
Dairy products 400-600 3-10 times Yeast , moulds, No impact on sensory,
( milk , cheese) E.coli etc. nutritional and
6% functional properties
Sea food 350 - 400 2 times Salmonella, Shucking and meat
( Vibrio, Anisakis extraction
Molluska,ready etc
to eat ) 16%
Fruits and 400-600 3-10 times Spoiling Healthier food rich in
Vegetables microbes ( yeast vitamins,minerals etc
( juices , etc)
sauces,onions And pathogens.
) 47%

7. MICROBIAL EFFICACY
 Inactivates most vegetative pathogenic and spoilage microorganisms at pressures
above 200 Mpa at RT.
 causes damage to cell membranes and denatures some intracellular proteins
leading to cell death.
 Reduced pH is generally synergistic with pressure in eliminating microorganisms.
 The process can also sub-lethally stress or injure bacteria.
 Bacterial spores >gram positive > gram negative > moulds, yeast (pressure
resistant)
 Inactivation of key enzymes, including those involved in DNA replication and
transcription is also mentioned as a possible inactivating mechanism.

8. USES
 Increased product shelf life - even for food which is sensitive to heat
 Low-temperature preservation method: no loss in product quality compared to
heat pasteurization.
 Enhanced food safety due to inactivation of spoilage organisms and relevant
food borne pathogens
 Processing in final consumer packaging is possible, free preservation of food by
using only pressure
 Production of “natural”, safe value-added food with a superior quality
 Homogenous effect of HPP: Results are independent of product size and
geometry
 Further benefits like large yield increase compared to traditional processes (e.g.
extraction of lobster meat from the shell)
 Waste-free and environmentally friendly, sustainable technology – only water
and electricity are needed