Although both batch process and semi-continuous HPP systems are available on the market, the
majority of food products are processed using batch process systems. A typical HPP batch system
(Figure 2) consists of four key components – the pressure vessel, pressurization fluid, intensifier, and
pump. Alternatively, the pressure vessel can additionally be designed as a pressure intensifier. The
pressure vessel is built to withstand a certain amount of pressure and temperature, and contains the
packaged food product and pressurization fluid. Pressure vessel sizes are defined by the volume of
fluid that the vessel can hold, and can range from several milliliters for research units to several
hundred liters for commercial units. The pressurization fluid is typically water, and is added to the
pressure vessel to eliminate air pockets between the packages of food. Once the pressurization fluid
is added, the hydraulic pressure intensifier and pump are used to increase the pressure inside the
cell and the pressure is transmitted through the pressurization fluid through the packaging material
to the food itself. As the pressure is applied uniformly over the whole surface of the food product,
the shape of the food is maintained.