Saturday, June 21, 2014

New technology with great potential –



Pulsed Light: Overview of the use in packaging:
Faster and better – linked to social and demographic changes, trends and preferences, the number of pre-packaged and ready to eat foods in the trade is increasing rapidly. To correspond with regard to organoleptic, diet Aryan, hygienic and toxicological aspects of the ever-increasing expectations, new, gentle but also effective technologies and processes are being developed. The strong demand for minimally processed foods makes the “Pulsed Light technology” for both current and future markets attractive.


Microbiological examination (photos: ACR / Alice Lace)

Microbiological examination (photos: ACR / Alice Lace)

Pulsed Light (English Pulsed Light, PL) is one of the emerging, non-thermal decontamination process, which is characterized by a non-selective inactivation of microorganisms and at a variety of foods and food contact materials such as packaging materials can be used.

Currently, further research is needed to close gaps between basic research and applied research. However, it is anticipated that the technology is used more and more in the coming years.

As a further development of decontamination with continuous UV light (coherent radiation of a defined wavelength), the PL technology to the generation of High voltage pulses are returned which (a plurality of J cm-2) are converted in succession light pulses of short duration (microseconds to s), high frequency (up to 10 Hz) and intensity. The lamps used for this purpose are usually inert gas lamps (primarily xenon gas-filled), which emit radio (light) in a wide range of 180-1100 nm (UV to IR) and thus largely reflect the spectral composition of sunlight. The intensity of the emitted light pulses is sufficiently strong to bring about 20,000 times the intensity of sunlight on the surface of the earth to a significant decontamination.

The extent of decontamination depends on three main factors. These are (i) the treated matrix such as liquid or solid state, (ii) the nature and characteristics of microbial contamination, and (iii) the process parameters such as device structure, intensity, and duration of treatment.

influence : Matrix
addition to clear liquids PL is mostly used for the decontamination of surfaces. This is due to the fact that for a sufficient penetration of the radiation into the matrix is ​​a low-reflection, high absorption and transmission coefficient condition which is not fulfilled by most (semi) solid bodies as food. This should a priori, however, not be regarded as disadvantageous as, for example, washing solutions also act on the surface.

In addition, the treated surface should be as free of irregularities, as these microbial contamination protection from the incident radiation can offer. The same applies to light-absorbing organic or inorganic matter between the light source and the contamination.

Last should the matrix itself only a few substances which can contain competitively absorb light. These substances are, for example, fats and proteins. Carbohydrates, however, do not show this effect is pronounced.

from goods receipt to output PL can be used at various stages of the production chain of a company. On top of this, for example by decontamination of food and food contact materials, the microbial load in production and thus the likelihood of recontamination of processed goods already be lowered. Furthermore, PL can be used to prevent cross-contamination or decontamination of the manufactured goods. The latter can occur before, in the use of appropriate packaging materials, but are also decontaminated after packing. Prerequisite for the use of PL after packing is mainly the transparency of the (plastic) material to the radiation. In addition, however, the packaging should have a suitable product protection, process stability and compliance with the provisions of law

influence. Contamination
Inactivation of microorganisms by PL is based on a non- selective process that overwhelms the cell functions and therefore leads to death. In this context, three effects which are parallel or in series to contribute to cellular damage, to be identified. These are photochemically (DNA damage), thermal (cell destruction and bringing about structural damage) and physical (structural cell damage) caused. How far these effects are pronounced, it depends on the energy input, the light spectrum as well as by the microorganism itself. Seem, for example, Gram-positive to be more resistant, in contrast to Gram-negative bacteria. As there is potential for sublethal damage to the microorganisms, it is recommended to incorporate the technology into a hurdle concept. Efficiency are increased by the use of photosensitizers (dyes). These form by irradiation from free radicals, which damage the microorganisms on oxidative pathways in addition.

Currently, however, the research also deals with issues such as inactivation, repair mechanisms and possible development of resistance of microorganisms.


influence: process parameters
Generally carries the entire spectrum of the emitted radiation for the inactivation of microorganisms with. However, since shorter wavelengths higher energy transfer, the UV (C) fraction is of particular importance. Although filters allow flexibility in the wavelength setting, however, the exclusion of radiation below 300 nm minimizes the Dekontaminierungserfolg significant. By measuring the UV or energy output of the addition, the system performance can be checked and corrected if necessary. Another important process variables are the fluence (J m-2), the pulse duration (s) and frequency (Hz). This is also influenced by factors such as disinfection rate, treatment temperature and sensory influence of matrix components (for example, lipid oxidation)
. For the successful implementation of PL, it is crucial as a result, pay attention to the structure and geometry of the system. So the positioning and orientation of the lamps should allow a uniform and complete irradiation of the matrix. This may be achieved for example by a plurality of lamps, movement of the matrix and transparent areas of conveyors and reflectors. And the absolute and relative distance between the lamp and the matrix is ​​an important determinant, because the shorter the distance the greater the vertical effect and the matrix and heating the frame, the smaller the effective treatment. From this follows the general trend towards short intervals and treatment times. On the flip side, however, can thus globular body, even if they are rotated about an axis that is difficult to decontaminate evenly. Remedy therefore provide greater distances and longer treatment times. The relative distance, however, influenced the results due to the fact that the intensity of xenon lamps decreases from the geometric center to the ends.

advantages and disadvantages of technology
side the extent of decontamination is crucial in deciding for or against a new technology, whether an improvement of food safety and the minimum durability date is given and remain organoleptic and nutritional characteristics of the food. In addition, it is checked whether residue freedom, convenience and efficiency are given and no rejection on the part of consumers or legislators there.

PL can generally be viewed by the user as a secure technology. However Automatic shutdown of the system when opening the aperture as well as a removal of ozone are a precondition for this. In addition, PL can reduce or even replace, which allows a residue-free food production the use of chemicals, disinfectants and preservatives. Also ask the xenon lamps used a good alternative to the mercury lamps used in the treatment with continuous UV light dar.

In addition to the ease of use of the technology are the short treatment times, the small footprint, the ability to batch-wise or continuously work and lack of warm-up phases, the clear strengths of the technology. Existing continuously operating UV systems can also be easily converted to PL.

The investment costs for industrial plants can discourage the purchase intention and make the technology particularly for certain market situations and the high-price segment interesting. Reasons for the high cost is due to the complex circuitry, which in the 10 to 100-fold and are for the highest possible UV output and long lamp-life (6 to 12 months) are essential in comparison to continuous light. The fact that the bulbs are more expensive, but is offset by the low running costs.

The strong demand for minimally processed foods makes the PL technology for both current and future markets attractive. However, marketing problems can arise from consumers due to misunderstandings, if the negative lossy term “irradiation” instead of, for example “light” is used, even though PL does not affect ionizing. Thus, properly selected information on technology increase the acceptance by the consumers.

While the FDA evaluated in 1996 the PL technology from a technology-oriented access and with a maximum permissible fluence of 12.0 J cm- 2 has been approved for food, the legal status in the EU is not clearly defined to date. One possible approach would certainly be those established by Regulation (EC) No 258/97 on novel foods and novel food ingredients. In current projects, the OFI research in Vienna on the applicability of the pulsed light for decontamination of packaged and exposed meat and meat products as well as the impact of treatment on the packaging material

authors. V. Heinrich, A Petschnig, B. Ecker, M. Washüttl, J. Bergmair, OFI





ofi Austrian Research Institute for Chemistry and Technology

Arsenal, Objekt 213, Franz-Grill-Straße 5
1030 Vienna Austria

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