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Ultraviolet light pasteurisation (UV)
Ultraviolet processing involves the use of radiation from the ultraviolet
region of the electromagnetic spectrum for purposes of disinfection.
Typically, a wavelength of 100 to 400 nm is used. The germicidal
properties of UV irradiation are mainly due to DNA mutations induced
through absorption of UV light by DNA molecules. UV light does not
penetrate opaque liquids such as milk. However, the use of high
turbulence and the correct positioning of lamps makes it possible to
reach the entire volume of liquid. In this way UV treatment, which
was previously limited to clear liquids such as water and wine, may
now be applied to fruit juices and milk. The latter requires regulatory
approval. The power requirement is as low as 10 kJ per kg, making it
an attractive process from an energy efficiency point of view.
High Pressure Processing
High Pressure Processing (HPP), also described as High Hydrostatic
Pressure (HHP), or Ultra High Pressure (UHP) processing, subjects
liquid and solid foods, with or without packaging, to pressures between
100 and 800 Mpa. The application of the pressure may be pulsed.
Treatment times vary between milliseconds and 20 minutes. The cost
of the process is high owing to the cost of the containers that will
withstand the pressure. Despite the high cost commercial applications
for HPP cover a wide range of products. Energy requirements should
typically be 20 to 30 KJ/kg processed.
Induction heating
In inductive heating, electric coils placed near the food product gen-
erate oscillating electromagnetic fields that send electric currents
through the food, primarily to heat it. Such fields may be generated
in various ways, including the use of the flowing food material as the
secondary coil of a transformer. Commercial applications of this pro-
cess include the sterilisation of milk at temperatures above 140°C and
the pasteurisation of liquid egg. Tubular modules are used for these
operations. Because this is a heating process the energy requirements
would appear to be similar to those of conventional pasteurisers. Heat
transfer coefficients, however, are higher leading to shorter warm up
times and little heat is retained in the machine after switching off, thus
alleviating the problem of burn-on on heating surfaces.
Sanitation processes
Traditionally sanitation in the food industry is achieved by heat and
by the use of chemical sanitisers. The use of Ozone (O3) and Electro-
chemically Activated (ECA) water are relatively recent innovations that
allow sanitation using compounds that are transient and will thus not
have any long term effects on the food products.
Because of its relatively short half-life, ozone is always generated
through corona-discharge. It is widely used in the food and beverage
industries both in gaseous form and dissolved in water. Sanitation of
cold room spaces and the rinsing of bottles prior to filling are typical
applications.
ECA water is produced by a process which converts tap water or salt
water into two products:
• Anolyte which is used as a disinfectant
• Catholyte which is used as a detergent
The process is similar to the salt chlorinators used in swimming pools.
ECA is also finding wide use within the food industry.
Energy – the whole process
It is important that the energy analysis of novel or innovative process-
es is not taken in isolation but incorporated into the factory design
as a whole. An example of energy analysis needing to be holistic is
in the comparison of flash and tunnel pasteurisation for carbonated
beverages. A large flash pasteuriser may require approximately
30 kJ/kg product energy input whereas a tunnel pasteuriser will
consume 130 kJ/kg on the same process. However, if the product is
bottled cold, as it would be in the case of carbonated beverages, then
condensation on the bottles post filling will need to be prevented. The
heaters required to do this will require approximately 105 kJ per kg.
If the cold water produced in the warming cannot be utilised elsewhere
in the factory then the flash pasteuriser, which initially looks to be much
more efficient, will not produce any energy savings.
Conclusion
Many of the innovative pasteurisation, sterilisation and sanitation
processes that have recently been developed in the food industry
can be used to improve the quality of foods and beverages. There are
possible reductions in energy requirements when these processes are
used. However, they need to be analysed holistically.
Definitions
• Pasteurisation is a process designed to control pathogenic
organisms and some spoilage organisms
• Sterilisation, a more severe process than pasteurisation, is de-
signed for the control of all pathogenic and spoilage organisms
Bibliography
[1] The Food and Drugs Administration of the United States.
forFoodProcesses/ucm100158.htm.
[2] Barry Wehmiller.
events/Documents/2011_03_10PasteurizationTechnologies.pdf.
[3]
[4]
[5]
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[9]
[10]
Websites were accessed during the period June – July 2015.
39 ENERGY EFFICIENCY MADE SIMPLE 2015