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DEVELOPMENT OF A LOW COST, FAST AND SECURE SYSTEM FOR EGG STERILISATION USING AN ATMOSPHERIC PRESSURE PLASMA SYSTEM

Final Report Summary - EGGSTERILISATION (Development of a low cost, fast and secure system for egg sterilisation using an atmospheric pressure plasma system)

Within the last decade there has been significant growth in the use of egg products for both home and commercial use, with current worldwide production at 55 million tonnes (up from 32.5 million in 1985). The largest egg producing countries are China, Russia, the United States of America (USA), Japan and Mexico, with the European Community (EC) producing 16% of the total world output. The leading European Union (EU) producers are The Netherlands, Spain, France and Italy. Within the EC, The Netherlands is the leading export country with 76 % of its production going to other EC countries. EC countries are large traders of eggs but almost all among themselves. Although egg consumption varies from country to country, per capita egg consumption in the EU is expected to increase to 15.1 kg/head by 2013 (equivalent to approximately 7.1 mt).

Each year, food borne pathogens lead to numerous sick days from work, needless deaths and large public health costs. Annually, Salmonella alone infects over 160 000 individuals in the EU, of which approximately 200 die. According to the World Health Organisation (WHO), food borne diseases will soon become the second largest cause of mortality in Europe, with annual costs for Salmonella-related illness estimated to reach EUR 2.8 billion. Salmonella can be transmitted to eggs either directly from infected hens or during manipulation. In most cases, contamination of the egg initiates at the egg shell. The most usual contamination is due to hens that have the bacteria in their digestive tract, infecting the eggshell but not the interior of the egg. In the EU, there have been scattered outbreaks of food borne illness due to this organism in the past several years and fresh unbroken egg shells are considered to be one in a growing list of 'potentially hazardous foods.' Salmonella infection can be easily transmitted during food processing and cooking since the bacteria contaminates other foods during manipulation, or can pass directly through the shell to the egg content. Salmonella Enteritidis can be inside healthy-appearing eggs and does not usually affect the taste, smell or appearance of the food. If eggs are eaten raw or undercooked, the bacterium can cause illness.

EGGSTERILISATION project will provide the egg industry with a safe, cheap and reliable egg shell sterilisation system based in atmospheric plasma. Plasma sources have been extensively used in the industry for several applications, being the sterilisation one of the most used.

Project context and objectives:

The objective of this project lies in the application of gas plasma produced at atmospheric pressure for the effective sterilisation of eggs. Gas plasma is currently utilised in a variety of applications for its low operating costs and non-polluting capabilities. The proposed system must to fulfil all the following objectives:

1. the application of the atmospheric pressure gas plasma will be applied directly onto the eggs and the process will be operated at a rate between 5000 and 10 000 eggs per hour;
2. the process must not significantly increase the temperature of the egg (lower than 5 ºC). This is paramount for ensuring that the nutritional quality of the egg is in no way jeopardised by the sterilisation treatment;
3. reduce the bacterial concentration of the surface of the egg from 0.01 % up to the 0.0001 % of the initial concentration. Tests will be carried out to measure the effectiveness of plasma exposure in removing bacteria and results will be evaluated to optimise the process;
4. ensure the process is clean and safe by using inert gases (e.g. helium or argon) to generate the plasma. Given that no chemical products will be used for disinfecting the eggs, there will be no harmful residues left on the surface of the shell, nor will there be any risk of contamination through the porous shell to the interior of the egg;
5. ensure that the disinfection process does not harm or damage the delicate eggshells, a vital requirement for industrial packing applications. The plasma source used will operate at atmospheric pressure, avoiding low-pressure technologies;
6. ensure that the disinfection process is low cost, amounting to a very small contribution to the total cost of the egg. It is estimated that the total cost of the process will not exceed two cents (EUR) per egg. Furthermore, the overall initial capital outlay for the EGGSTERILISATION equipment selling price will need to be in the region of EUR 30 000 in order to make it accessible for small and medium sized enterprises (SMEs);
7. facilitate easy installation and integration in fast, modern egg production or packing lines. A continuous plasma generation source will be used in order to render the EGGSTERILISATION system as flexible and as fast as possible.

Project results:

The technical results of the project are mainly the design and construction of two different prototypes to sterilise eggs using atmospheric plasma. The first one is a laboratory prototype, able only to sterilise one egg, while the second one is an industrial prototype, able to sterilise 30 eggs at the same time.

The first result of the EGGSTERILISATION project was a laboratory plasma prototype. The objective of this prototype is to obtain a plasma system to test the most optimum sterilisation conditions to export them to a bigger prototype, able to operate in an industrial environment. The main subsystems of the laboratory prototype are:

1. Reactor:
Two different reactors were manufactured. One of them is totally built in PTFE constructed by UB, while the other one has only the dielectric barriers built in this material, manufactured by CRIC. Both reactors were similar, allowing only one egg inside. The material of the body of the CRIC reactor was built in PMMA since its UV transmittance was lower than the PTFE.

2. Electronics:
Two types of electronics were used to generate the plasma inside the reactor. One of them was based in a RF analog amplifier, while the other one was based in a half-bridge. The problem with the RF analog amplifier was the lack of voltage to ignite the plasmas with different gas mixtures. To improve this situation, a square wave generator based in a half-bridge was designed and manufactured. This scheme was the base for the future electronics used in the industrial prototype. The laboratory setup was able to withstand 250 V at 150 W.

3. Gas handling:
Three regulating valves were used to control the gas mixture in the reactor. Moreover, bubbling equipment was used to prepare humidify with water or hydrogen peroxide some of the gas mixtures.

4. Ultraviolet (UV) measuring equipment:
In order to obtain the UV emission of the different plasmas, a spectrometer StellarNet EPP2000 was used. Its measuring range was from 200 up to 2 000 nm (UV and visible range).

5. High voltage transformer:
The high voltage transformer used was an Information Unlimited FLYPVM+ transformer. It is able to generate 40 kV with an output current of 10 mA.

The EGGSTERILISATION main result is the manufactured industrial prototype, able to sterilise 3600 eggs per hour. The system is able to sterilise 30 eggs in 20 seconds, but around 10 seconds are needed to move the cover, to load the eggs inside the reactor and all the operations of the prototype are fully automated except the egg charging. The subsystems that form the prototype are listed below.

1. Automation:
Controls all the sterilisation process. The main core is a Siemens S7-200 PLC system. The main tasks are: electrical security (overcurrent and differential switch), control of the safety devices, managing alarms, control of the gas handling subsystem, pneumatics handling, control of the plasma ignition, resonant frequency search and providing low voltage power supplies (24 V and 12 V).

2. Electronics:
Half-bridge converts a 12 V square signal into a high power signal to be transformed by the high voltage, high power transformer. It has an output series capacitor that provides a resonance primary frequency that will be used to amplify the output voltage. This component was designed and manufactured by CRIC. It is able to generate square signal up to 250 V at a maximum mean power of 3 kW. Processing process control block (PCB): Converts the relevant information provided by the half-bridge to direct current (DC) levels to be read by the PLC. Also designed and manufactured by CRIC. DC power supply: feeds the half-bridge system with DC power. It is a commercial power supply, model Elektro-Automatik EA PS 8360 - 30R 2U.

3. High voltage transformer:
Converts the output signal from the half-bridge in a high voltage signal, which will be feed into the reactor to generate the plasma. Manufactured by APP, generates up to 30 kV and it is able to withstand up to 30 kW with oil refrigeration.
Gas handling: This subsystem is used to fill the reactor with a mixture of noble gases to create the plasma. It is composed mainly by two control electrovalves, three regulating valves to change the gas mixture in the reactor and a pressure switch to avoid igniting the plasma when there are no gases inside the chamber.
Plasma reactor: It is the mechanical airtight chamber where the eggs are introduced and the plasma generated. The pneumatic system is in charge of moving the superior cover of the reactor to allow the introduction of the eggs inside it. It has been designed and manufactured by CRIC.
Pneumatics and mechanics: The mechanic structure and the pneumatic part are used to move up and down the reactor superior cover. All the mechanic structure has been designed in aluminium to reduce the weight.

The main differences between the laboratory and the industrial prototype are:

1. Amount of eggs sterilised: The laboratory prototype can sterilise only one egg, while the industrial prototype was able to sterilise up to 60 eggs (the final version was designed to sterilise only 30 eggs).
2. Gas handling: The laboratory prototype used continuous gas flux, while the industrial prototype was airtight and the gas was filled only once.
3. Power: The industrial prototype power was around 3 kW, while the laboratory prototype used only 150 W.
4. Automation: The industrial prototype was fully automated.

The scientific results are also remarkable. More than 1500 eggs have been treated with several types of plasma. The sterilisation rates obtained varied between 90 % and 99.95 %, depending on the plasma conditions and the time exposition. The gas mixtures employed are:

1. helium 100 %;
2. helium 98 %, oxygen 2 %;
3. helium 70 %, argon 30 %;
4. helium 100 %, relative humidity 10 %;
5. helium 100 %, relative humidity 50 %;
6. helium 96 %, oxygen 4 %;
7. argon 100 %;
8. helium 50 %, argon 5 0%;
9. helium 70 %, argon 30 %, relative humidity 15 %;
10. helium 40 %, argon 60 %;
11. argon 100 %, relative humidity 90 %;
12. krypton 100 %;
13. helium 90 %, krypton 10 %;
14. argon 90 %, krypton 10 %;
15. argon 95 %, krypton 5 %;
16. helium 70 %, argon 30 %;
17. helium 70 %, nitrogen 30 %;
18. helium 90 %, carbon dioxide 10 %;
19. argon 9 %, carbon dioxide 10 %;
20. helium 33 %, argon 33 %, nitrogen 33 %;
21. helium 40 %, argon 40 %, nitrogen 20 %;
22. helium 60 %, argon 10 %, nitrogen 30 %;
23. helium 40 %, argon 40 %, nitrogen 20 %, saturated with hydrogen peroxide;
24. helium 100 %, saturated with hydrogen peroxide.

Several types of salmonella enteriditis and other bacteria have been tested during the project:

1. Salmonella enteritidis 1049-1-99
2. Salmonella enteritidis 61-358-1
3. Salmonella enteritidis SGSC 2275
4. Pseudomonas fluorescens ATCC 17400
5. Proteus mirabilis ATCC 14153
6. Proteus vulgaris DSMZ 30118.

Potential impact:

The EU egg industry consists of an estimated 5000 SMEs across Europe involved in both egg production and packing. Reduced profit margins of the EU sector as a whole and SMEs in particular, have resulted from a number of threats, the most prominent of which has been zoonosis. The EU ban on traditional cages for laying hens, scheduled for phase out by 2012 (Directive (1999/74/EC), could cost EU-25 egg producers up to EUR 354 million per year. With regards to Salmonella, in Denmark for example, the current control costs for layer hens and broiler chickens are estimated to be in the range of EUR 3.06 million per year. Animal producers and the food industry bear almost exclusively these costs which, in turn, are passed on to consumers via higher prices. Based on the figures above, the increase for poultry is equivalent to approximately EUR 0.015/kg of broiler or egg. These costs have a heavy impact on the SME producer who is at a disadvantage when costs for recuperating financial losses must come from higher product prices, as SMEs cannot compete with large enterprises (LEs) in economy of scale, often being unable to take advantage of market opportunities that require large production quantities and regular supply.

This technology will not only benefit poultry and egg enterprises in western Europe, but also in central and eastern European countries (ECC). ECC countries present new and vibrant markets for SME consortium equipment suppliers, as agricultural enterprises are now subject to 80 000 pages of EU regulations governing sanitary, phytosanitary, veterinary and animal welfare standards. Agricultural SMEs that cannot meet standards due to expensive and complex equipment and control procedures, among other factors, will be forced out of the market. Thus, access to the EGGSTERILISATION technology will be fundamental for ECC sector SME customers as the financial implications of increasing regulations and consumer demands are stimulating market consolidation in favour of large, capital intensive agricultural producers. Both within Europe and internationally, EGGSTERILISATION promises great potential for the organic foods market, as this innovative technology is a non-invasive, chemical-free method that does not damage or compromise egg quality and nutritional value. Together, consumer purchases in the United States of America (USA) and EU make up 95 % of the estimated EUR 19 billion or USD 25 billion world sales of organic food products. EGGSTERILISATION will provide partner SMEs with a cost effective, practical technology for the marketing of a safer animal food product which will undoubtedly lead to more confident consumers and foment greater industrial relations in the food processing sector, such as chain supply production, optimising financial and human resources and resulting in increased profitability and competitiveness.

From an EC investment point of view, we should also consider the benefits related to the savings in health costs due to a minor number of salmonella outbreaks in EU country users of the EGGSTERILISATION system. Salmonella was, as in previous years, the most commonly reported cause of food-borne outbreaks in the European Union. Detailed information on implicated foodstuffs (food vehicle) was reported in 68.8 % of the verified outbreaks. The most common single food vehicle in the outbreaks was eggs and egg products, responsible for 14.6 % of the outbreaks. S. Enteritidis was the most common serovar involved and eggs or products thereof were the most frequently implicated foodstuffs in these outbreaks.

The final users of the EGGSTERILISATION system are egg producer and packers (hatching and human consumption eggs) and egg products manufacturers. The hatching egg producers will increase their margins due to an expected increase in the birth ratio (the amount of chicks that are born due to a lesser amount of bacteria in the egg shell). The egg producer will produce a safer egg and the egg products manufacturers will reduce their pasteurisation costs, since the egg products will have a lower amount of bacteria. The technical SMEs of the project will have a wider market to sell their products, because of the new market opened.

Ovobel will be the main distributor and manufacturer of the future EGGSTERILISATION machine. They will pay royalties to the rest of partners of the consortium each time they sold a new EGGSTERILISATION machine. There is no initial intention of creating a new spin-off from the project and there is no need for the inclusion of third parties, since all the aspects of the EGGSTERILISATION manufacturing process are covered by the consortium.

A project website (see http://eggsterilisation.cric-projects.com online) has been created for dissemination purposes. It is also being used as a communication tool between the partners.

The website is divided in two parts: a public and a private site. In the public site, there is available general non-confidential information about the project (including its goals, objectives, project partners), while in the private site the most relevant confidential documents of the project can be found (e.g. meeting minutes and presentations, periodical reports or technical deliverables). These documents can be viewed and downloaded at any moment by the project partners. Therefore, the web site also complies with the purpose of providing a permanent and updated record of all information published and distributed by the project. The private site can be accessed by means of specific user names and passwords created at the beginning of the project. The website and its contents are constantly being updated, expanded and improved, both in terms of functionality and information volume while the project proceeds.