Less energy usage is claimed
for novel pasteurisation process
Source of
Article: http://www.foodproductiondaily.com/Quality-Safety/Less-energy-usage-is-claimed-for-novel-pasteurisation-process By Jane Byrne, 20-Mar-2009
A new way of sterilizing packaged foods
that offers rapid results and less energy consumption has been the focus of a
recent project undertaken by the German research group, the Fraunhofer
Institute for Process Engineering and Packaging.
At the Anuga FoodTec show in Cologne last week, leading Fraunhofer
researcher, Thomas Pfeiffer, spoke about the heating process that is based on
the application of radio
frequency fields inside a water bath. He said that while somewhat similar research has been carried out in
North America, the Fraunhofer project is unique in European terms. According to Pfeiffer, the radio-frequency water bath method can be
used for many food heating tasks as long as the food is tightly packaged and
the package is transparent for the electric field. Low energy
consumption Speaking to FoodProductionDaily.com, he said that the method overcomes
many of the restrictions of current sterilization
techniques, which have high energy consumption, and it also improves on the
newer microwave heating and conventional radio frequency methods that, he
claims, can result in limited penetration and edge overheating. Pfeiffer said that there has been a lot of interest in the project
from the food processing sector: “What attracts the interest of industry is the possibility to speed
up the heating of food packages by a factor of about 10 and, moreover, the
prospect of replacing energy consuming autoclaves by a continuous process
that requires less energy and saves on time and space.” Heating process He said that the method uses two flat plate electrodes as applicators,
with the space between the electrodes being filled with de-ionised water and
the food packages then immersed in this space: “Due to its high dielectric constant, the water is a much more
efficient transfer medium for the electric field than air, and without
slowing down the heating process, water as medium enables the reduction of
electrode voltage by about one order of magnitude, thus eliminating the flash
over you get with standard radio frequency heating.” Package testing The project team tested a number of different packages, said Pfeiffer,
including pouches and vacuum pouches made from PA/PE or other films, CPET
trays, glass jars with metal screw caps and plastic sausage casings. “The one requirement is that the package is hermetically tight and the
packed food will not contaminate the de-ionised process water. Metal packages
like cans cannot be used, since they are not transparent for the electric
field,” he said. Pfeiffer said that the team is currently evaluating the compatibility
of the heating process with polar film materials in thin layers such as EVOH.
“We want to apply the process to as many different food products as
possible. Cook/chill convenience foods are an interesting category for rapid
and quality retaining heating to better preserve their freshness of
character. “Ultimately, we have to try each food product and package format in
order to judge its viability for sterilization by this method.” Best in class He said, though, that the team has achieved the best heating results
so far with homogeneous foods such as single solid blocks of food material
like tofu slices, cylindrically formed sausages, and jars filled with liquid
or solid liquid mixtures. Pfeiffer said that the method has also been used to cook or boil
products like large sausage for cold cuts, while using the process for rapid
boiling of ham is also an option. Quality control He maintains that the team did not see any negative effects on products
in the hundreds of experiments they conducted with real food packages. “Indeed, we have seen quality improvement in products through the
reduction in thermal processing time with benefits including juicier fish or
less softened vegetables.” Combination of factors Pfeiffer said that in order to obtain simultaneous microbiological
safety and the least possible thermal degradation of the product, it is
important to have a very good temperature control. According to Pfeiffer, there is no inherent temperature limit in the
radio frequency water bath heating process itself, but that the team’s
experiments were generally conducted at temperatures of up to 95°C. “We try to heat the whole product volume rapidly to the required
temperature without overheating parts of the product. In order to achieve
this, we have to work on finding the best combination of process parameters
for the specific product and package. “This involves parameters like electrode voltage and exposition time,
but also package positioning and orientation towards the electrical field
vector and using shaped electrodes to improve uniformity of the electric
field inside the food product.” |
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