High pressure processing (HPP) is a promising
“non-thermal” technology that has been developed
with the aim of obtaining microbiologically safe food
products while avoiding undesirable changes in the
sensory, physicochemical, and nutritional properties
of foods. Thus HPP has become one of the
innovative food processing technologies most
accepted by consumers.
First research in 1890s – Milk Pathogens.
Non-thermal processing technology (combination
with heat possible).
First commercialized in Japan in the early 1990s
for pasteurization of acid foods for chilled storage.
High pressure treated foodstuffs have been
marketed in Japan since 1990, in Europe and the
United States since 1996 & Australia since 2001.
Rapid commercialization since 2000.
High pressure processing (HPP), is a method of preserving
and sterilizing food, in which a product is processed under
very high pressure, leading to the inactivation of certain
microorganisms and enzymes in the food.
Also known as Pascalization.
High Pressures applied at short periods of time (20minutes).
Application of high pressures can cause:
Inactivation of Parasites, Plant cells.
Some fungal spores.
Many food borne viruses.
Enzymes are selectively inactivated.
Macro molecules can change conformation.
Small molecules (eg: flavors) are generally unaffected
High pressure is instantaneously and uniformly applied
to the sample.
Compression is fully reversible.
Pressures exerted at highest altitudes
(0.01 to 0.1 MPa) and deepest part of
the oceans (10-100 MPa) are usually
considered as High pressures.
For food processing, 200-800MPa
pressure is required.
For inactivating milk enzymes; alkaline
phosphatase and protease about
1000 MPa is needed (as per research
Usually, 600MPa is the optimum
pressure for processing commercial
High pressure can kill microorganisms by interrupting their cellular
function without the use of heat that can damage the taste,
texture, and nutrition of the food.
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: 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 dependent 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.
HPP systems are available in two types:
A typical HPP batch system consists of four key components:
A typical HPP process uses food products packaged in a high-barrier, flexible
pouch or a plastic container. The packages are loaded into the
The vessel is sealed and the vessel is filled with a pressure transmitting fluid
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.
Pressure and temperature profile during a typical HPP treatment applied to food.
Low-medium moisture, semi-solid/solid foods, vacuum packaged:
Dry-cured or cooked meat products
Fish, seafood, marinated products
Ready to eat meals, sauces
High moisture, solid foods, vacuum packaged:
High moisture, liquid foods in plastic bottle/flexible packaging:
Solid foods with air included
Bread and cakes
Packaged foods in completely rigid packaging
Foods with a very low water content
HPT finds application in food preservation in many ways. Some example of
areas where HPT has more potential are:
Fruits and Vegetables
Meat and Fish Industry
Fruits and Vegetables:
Shelf life extension.
Inactivate microorganisms and quality-deteriorating enzymes
Higher sensorial, functional and nutritional values while improving food
Puree, coulis, sauces, juices, smoothies, chunks, slices, ready-to-eat
products, these are only some examples of a wide range of fruit and
vegetable products that can be processed by HPP.
One of the most successful commercial application of HPP nowadays is
definitely preservative-free guacamole (avocado puree with spices)
because the process maintains avocado flavor, texture, green color without
sacrificing food safety or shelf life (upto 6 weeks under chilled conditions).
Meat and Fish Industry:
Extends shelf life with no effect on flavor or nutrients.
Inactivate microorganisms and quality-deteriorating enzymes.
Maintaining high sensorial and nutritional qualities and improving food
safety without the need of additives or artificial preservatives.
Sliced ham, turkey or chicken cuts, ready-to-eat products, whole pieces
of cured ham, these are only some examples of products.
One of the most successful commercial application of HPP nowadays is
easy shell opening of molluscs, easy meat extraction of crustacean
products and helps in increasing the yield upto 45%.
Increased shelf-life (3 to 10 times longer than the same product without
HPP stored at same temperature).
No impact on sensory, nutritional, or functional properties.
Effective elimination of spoilage and pathogenic microorganisms.
High Pressure Process Technology works especially well on acidic dairy
products such as yogurt because most pressure-tolerant spores are
unable to survive in environments with low pH levels. The treatment is very
effective on both solid and liquid dairy products. Since high pressure acts
quickly and evenly, neither the size of a product’s container nor its
HPP is the best option to preserve and respect
the functionality of thermosensitive bioactive
components present in colostrum such as
immunoglobulins, lactoferrin and growth factors.
Effects on Food Color & Flavor:
Fresh or marinated meat: Iron in the myoglobin changes from ferrous to
ferric and globin is denatured-the red color is lost.
Cooked meat color meat is largely unaffected.
Cooked meals are not affected.
Fruits and Vegetables: Slight modification
Fruit juices: Little or no affect.
Flavors are mostly unaffected.
Effects on Food Texture:
Slight softening in foods with cell wall structures.
Effects on Fats and Lipids:
Effects on Proteins and Enzymes:
Inhibition or stimulation of the enzymatic activity (depending on
Proteins are partially denatured in products where proteins have not
been previously modified by other process such as heating, drying and
Pressures affects hydrophobic bonds and electrostatic interactions.
Pressure denaturation is complex, at pressures >200 Mpa denaturation
HPP equipment are of two types.
Processed Product in Processed Product out
The standard in HPP industrial equipment:
Horizontal design for traceability and easy installation.
Special design for food industry (stainless steel, cleanable)
Automatic loading/unloading system
Working pressure up to 600 MPa (6000 bar).
Flexible packaging (>15% volume contraction)
Extra tight seals.
Rounded & reinforced edges.
Minimal head space.
Modified Atmospheric Packaging (MAP) possible
Tear strength, puncture resistance and surface smoothness generally
not affected by HPP.
Often flexible pouches or bottles are inserted in secondary cardboard
containers after processing.
USDA has approved HPP as an intervention method for listeria
contaminated pre-packed ready-to-eat (RTE) meat products.
U.S Food & Drug Administration (FDA) has accepted the commercial
use of HPP for application of low acid foods.
Consumers: HPP is a consumer acceptable, environmental friendly,
scientifically recognized method to achieve higher quality in certain foods
Processing: Pressure transmission is instantaneous, uniform, short
processing times, assured safety in whole pack, suitable for solids and
Quality: Retains flavor and nutrition
Environmentally: Safe and no process by products, no emissions‐
Packaging: Package design, geometry and format should be tailored for
HPP, Packaging films and laminate structure generally survive HPP well,
but MAP and HPP at high temperature can cause delamination and