What is High Pressure Processing?
High
Pressure Processing (HPP) is a new food treatment that can make food safer to eat and extend shelf-life
without reducing vitamin content and without altering flavour, texture or appearance. It can be carried
out at room temperature and the pressure used is immense (equivalent to the weight of 3 elephants on
a strawberry). The pressure is transmitted through water, which completely surrounds the packaged food.
As the pressure is equally distributed, there is no obvious crushing effect.
How
are foods pressurised?
Foods are pre-packaged in either a vacuum-pack
bag or in a flexible plastic bottle. Hard materials such as glass or metal cannot be used as they cannot
transmit the pressure through to the food. The packaging must be able to withstand a volume change of
up to 15%, followed by a return to its original size, without losing seal integrity or barrier properties.
The packaged items are placed in the pressure vessel. The vessel is sealed and filled with water.
A
pump is used to force more water into the vessel, creating hydrostatic pressure. The pressure is therefore
transmitted through the water into the food. The pressure is maintained for a pre-determined time (usually
between 30 seconds and 15 minutes). During this time many food poisoning and spoilage bacteria are killed.
When the pressure cycle is complete, the vessel is depressurised, opened and the product removed.
What
types of food can be pressure-treated?
HPP is suitable for foods that
have a high water content. It is particularly useful for raw foods such as oysters, fresh fruit juices,
salsas and guacamole, as the treatment does not significantly alter flavour, texture or appearance.
HPP products that are commercially available worldwide include: Fruit juices and smoothies, fruit purees,
jams and jellies, avocado halves and guacamole, cod (dried and salted), oysters (shucked and in-shell),
cured ham, tapas selections, ready-to-eat meal kits (cooked chicken or beef, along with salsa, guacamole,
onions and peppers).
