Agriculture Reference
In-Depth Information
temperature (Aertsen et al., 2009). The introduction of HPP
in food preservation has started in the early 1990s in Japan
(commercial sense). Over the last 2 decades, HPP technol-
ogy has been increasing steadily and is considered as one of
the best novel processing technologies of recent time.
A recent consumer acceptance indicated HPP remains
ahead of other novel processing technologies and has an
edge over the PEF processing (Olsen et al., 2010). Con-
sumer acceptance of HPP and PEF-treated products has
been investigated in the Americas (the United States and
Brazil), in Europe (Belgium, Czech Republic, Denmark,
Finland, France, Germany, Hungary, Norway, Slovenia,
Slovakia, Serbia, Spain, the Netherlands, the UK), and in
Australia. Fruit juices seem to be the most frequently in-
vestigated product among food products. In general, con-
sumers of HPP foods are inclined to be more positive to-
wards technology as it is easy to understand. Furthermore,
consumers prefer health-related benefits, taste-related ben-
efits, and environment-related benefits of HPP compared
to conventional heat treatment (Butz et al., 2003; Mireaux
et al., 2007; Nielsen et al., 2009). Consumers opined that
the advantages of the HPP technology should be mentioned
on the juice labeling rather than merely putting the name
of the technology on the label, for example, “HPP-treated”
(Deliza et al., 2005).
There are two principles that well describe the effects of
HP: (1) the principle of Le Chatelier, which describes that
any phenomenon (phase transition, chemical reactivity, and
reaction, change in molecular configuration) accompanied
by a decrease in volume will be increased by pressure. In
addition, the reaction rate increases with increasing temper-
ature (Arrhenius's law); and (2) pressure is instantaneously
and uniformly transmitted independent of the size and the
geometry of the food—what is known as the isostatic prin-
ciple.
The HHP of food generally relies on the application
of isostatic, hydraulic pressures in the range of 100-
1,000 MPa. The process can be carried out in any type
of hydraulic fluid but water is often preferred for ease of
operation and compatibility with food materials. Further-
more, water is relatively incompressible, and it stores much
less energy in its compressed state compared with gases
(Earnshaw, 1996). The HP chamber is filled with water,
and HP is generated by compression (direct or indirect) or
by heating the pressure medium. Once the desired pressure
is achieved, it maintains that level, and no additional energy
has to be spent.
High pressure equipment is very specialized and expen-
sive. Pressure vessels are constructed out of forged steel or
reinforced with tensioned wire windings (Earnshaw, 1996).
Currently, laboratory, pilot plant, and commercial-scale HP
equipment (batch, semicontinuous, continuous) is available
for different food applications. A list of manufacturers is
presented in Table 5.1. There are more than 90 HP units
Table 5.1. List of major distributors and manufacturers of HPP units.
Manufacturer/Distributor
Details of HPP Unit
Laboratory scale
UNIPRESS
Multivessel units; 800 MPa; cells containing optical windows
STANSTED
Multivessel units; max. 1,000 MPa, 1.0 liters
EPSI
Max. 1,000 MPa, 5.0 liters
FLOW
600-1,500 MPa, 1.5 liters
RESATO
Multivessel units; 800 MPa,
ALSTHOM
3.0-4.0 liters, 400-700 MPa; semicontinuous; 5.0 liters, 600 MPa
Avure Technologies
2.0 liters, 690 MPa
Commercial/pilot scale
Avure Technologies
35-700 liters and 600 MPa; continuous
ALSTHOM
50-500 liters, 500 MPa
UHDE
100 liters, 700 MPa, semicontinuous
KOBE STEEL
2
×
300 liters, 400 MPa
STANSTED
High-pressure homogenizer; 350 MPa
Elmhurst Research Inc.
700 MPa
Source: Modified from Knorr (2002).
 
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