High Pressure Processing (HPP) is a method of food processing where food is subjected to high pressures (up to 87,000 pounds per square inch or approximately 6,000 atmospheres), to achieve microbial inactivation or to alter the food attributes in order to achieve consumer-desired qualities. Pressure inactivates most vegetative bacteria at pressures above 60,000 pounds per square inch. HPP retains food quality, maintains natural freshness, and extends shelf life.

High pressure processing causes minimal changes in the fresh characteristics of foods and fruit juices by eliminating heat pasteurisation. Compared to heat pasteurisation, HPP results in foods with fresher taste, and better appearance, texture and nutrition. High pressure is conducted at refrigerated temperatures, which negates cooked off-flavors. The technology is especially beneficial for heat-sensitive products such as fruit juice.

Most processed foods today are heat treated to kill bacteria, which often diminishes product quality. High pressure processing provides an alternative means of killing bacteria that can cause spoilage or food-borne disease without a loss of sensory quality or nutrients.

In a typical HPP process, the product is packaged in a flexible container (usually a pouch or plastic bottle) and is loaded into a high pressure chamber filled with water. The water in the chamber is pressurised with a pump, and this pressure is transmitted through the package into the food itself. Pressure is applied for a specific time, usually 2 to 5 minutes. The processed product is then removed and stored/distributed in the conventional manner. Because the pressure is transmitted uniformly (in all directions simultaneously), food retains its shape, even at extreme pressures.

Like any other processing method, HPP cannot be universally applied to all types of foods. HPP can be used to process both liquid and solid foods. HPP cannot yet be used to make shelf-stable versions of low-acid products such as vegetables, milk, or soups because of the inability of this process to destroy spores without added heat. However, it can be used to extend the refrigerated shelf life of these products and to eliminate the risk of various food-borne pathogens such as Escherichia coli, Salmonella and Listeria. Another limitation is that the food must contain water and not have internal air pockets.