SIK report

OFFICIAL REPORT

SIK-Up98-9819 © DANÆG AIS (DK) - Dicam Microweaves ApS

Important: No other organization than Dicam Microwaves ApS may sale Microwaves systems based on the SIK-report Up98-9819, unless they have full autorisation by Danæg AIS (DK).

--> DOWNLOAD English report <-- click here

ConfidentiaI

THE SWEDISH INSTITUTE FOR FOOD AND BIOTECHNOLOCY

Official Report Up98-9819

Validation of Microwave Pasteurisation for Egg-Trays and
EUR-Pallets Contract work for DANÆG AIS

Emma Shah
April 1999
ConfidentiaI – This document may only be used by Dicam Microwaves
on behalf of DANÆG AIS

Confidential

PROJECT INFORMATION

Start of the project 5 October, 1998
End of the project 16December, 1998

The report was finalised
April, 1999

Checked by
Claes-Göran Andersson, Marianne Hedström, Ulf Rönner

Project leader
Emma Shah

Project group
Claes-Göran Andersson, Ewa Eriksson, Marianne Hedström, Farideh Taherinejad

Distribution list
Per Schyum, Danaeg AIS (2 copies); SIK archive; Claes-Göran Andersson, SIK;
Emma Shah, SIK.

Key words
Pasteurisation,microwave heating, egg tray, egg carton, BUR-pallet, temperature validation, microbial validation

© SIK1(13)

SUMMARY

Of environmental and economical reasons egg-trays used for transporting eggs from the production site to the packing facility have been re-used 2-8 times before they are discarded. Experience has shown that the egg-trays, produced from recycled fibers, may carry human and animal pathogens and are therefore a contamination risk. To maintain the materials and logistics used today it is therefore necessary to pasteurize the egg-trays.

The validation performed by SIK was comprised of two tasks: validating that the oven (Fabr. Nr. 81400, Svirco) could achieve a temperature of 90oC on the surfaces of the pasteurised material, and validating the killing effect of the process on 106 CFU Serratia marcescens. The pasteurisation process was validated for egg-trays and BUR-pallets with cardboard sheets.

Serratia marcescens has been used as an indicator organism to avoid work with actual pathogens as e.g Salmonella. Serratia marcescens is, as Salmonella, a member of the family Enterobacteriaceae.

The measuring points were evenly distributed in the processed material. In all 37 measuring points for egg-trays, a 40 minute processing time followed by a 45 minute holding time resulted in temperatures well above 90oC, and a killing effect of 106 CFU Serratia marcescens per measured point. In 37 + 9 measuring points for BUR-pallets and cardboard sheets, a 65 minute processing time followed by a 45 minute holding time resulted in temperatures just above 90oC, and a killing effect of 106 CFU Serratia marcescens per measured point.

The process demands that the steam given off during the process is contained around the processed material during processing and during the holding time, otherwise the desired temperatures will not be reached.

© SIK 2(13)

BACKGROUND

Of environmental and economical reasons egg-trays used for transporting eggs from the production site to the packing facility have been re-used 2-8 times before they are discarded. Experience has shown that the egg-trays, produced from recycled fibres, are a contamination risk of human and animal pathogens. To maintain the materials and logistics used today it is therefore necessary to pasteurise the egg-trays.

As a process was under development for surface pasteurisation of egg-trays placed on a BUR-pallet, the idea of pasteurising BUR-pallets was also born. Wooden BUR-pallets are a known contamination risk as they easily absorb moisture and therefore promote the growth of bacteria and mould. BUR-pallets are also transported between different places and can therefore carry an infection between different locations.

In earlier work at SIK, Contract Report Up 97-9434, the elimination of micro-organisms on egg-trays and BUR-pallets was studied. Based on this work DANÆG AIS let build a microwave hot-air oven for batch pasteurisation of eggtrays and BUR-pallets.

The pasteurisation process comprises a processing time in the oven and a holding time outside of the oven. It also includes the processed material to be enclosed in a diffusion proof hood to contain the steam given off by the material during the process. These procedures have been developed during the development of the prototype oven. The purpose of the pasteurisation process is to ensure that eggs are not contaminated by the tray material they are in contact with and that poultry pathogens are not transferred between production sites, i.e. to achieve a drastic reduction of vegetative pathogenic bacteria on egg-tray surfaces.

© SIK4(13)

GOAL

The validation performed by SIK was comprised of two tasks: validating that the oven (Fabr. Nr. 81400, Svirco) could achieve a temperature of 90oC on the surfaces of the pasteurised material, and validating the killing effect of the process CFU106 CFU Serratia marcescens.

The temperature measurements were to be repeated ten times, and the microbiological killing effect was to be studied by five replicates, at the least three The temperature and microbiology tests were combined.

PLANNING AND IMPLEMENTATION OF THE PROJECT

Pasteurization process
The microwave, hot air oven was equipped with 29.6 kW microwave power and 12 kW hot air power. During processing the oven was operated on full microwave power, and hot air circulation at 90oC. Also, the heated material was covered by a diffusion proof hood to contain the steam. The use of a diffusion proof hood results in the hot air having little or no effect on heating of the material.

The heating of materials with microwaves is dependent on the amount of water ifl the material, i.e. the moisture content. These trials were performed under real life conditions with a moisture content for egg cartons between 5 and 15 % and a maximum moisture content for BUR-pallets of 25 %. Especially for BUR-pallets the moisture content could differ greatly between different pallets or parts of a pallet, but there were no indications that this affected the temperatures measured.

© SIK5(13)

CONCLUSIONS

In all 37 measuring points for egg-trays, a 40 minute processing time followed by a 45 minute holding time resulted in temperatures well above 90oC, and a killing effect of 106 CFU Serratia marcescens per measured point.

In 37 + 9 measuring points for BUR-pallets and cardboard sheets, a 65 minute processing time followed by a 45 minute holding time resulted in temperatures just above 90oC, and a killing effect of 106 CFU Serratia marcescens per measured point.

The results are based on the use of the prototype microwave/hot air oven, Fabr.
Nr.81400 developed by DANÆG, as it was configured during the tests at SIK.
Also, the process demands that the steam given off during the process is contained
around the processed material during processing and holding time.

© SIK - Danaeg DK - Dicam Microwaves 2003

© SIK 13(13)

What is SIK?

SIK is an industrial research institute owned by the SIK Members’ Association (70%) and IRECO AB (30%). The purpose of the Institute is to strengthen the competitiveness of its members.
SIK has an annual turnover of approximately SEK 100 million. One-third of its income comes from the Swedish state via the National Swedish Board for Industrial and Technical Development (NUTEK), the Nordic Fund for Technology and Industrial Development, the EU, IRECO AB and research councils. The other two-thirds come from assignments and membership fees from industry via the SIK Members’ Association.
SIK conducts strategic and applied research for industry in accordance with a goal-oriented research programme and in the form of joint industrial projects.
SIK offers comprehensive consultancy services in product and process development and problem solving of both an acute and strategic nature.
SIK also provides advice and service in R&D matters.
SIK is the specialised resource for the co-ordination of R&D for the Swedish Food Federation (Li). SIK maintains a strategic alliance with the British research institute Campden & Chorleywood FRA.
SIK is a member of an international network made up of other centres of knowledge and communicates know-how, ideas and information via regular customer contacts, reports and seminars.
SIK provides tailored training courses for individual companies and participates in graduate and undergraduate course programmes at universities and colleges in Gothenburg, Lund and Uppsala. The Department of Food Science at Chalmers University of Technology is based at SIK.
SIK has around 145 employees, most of whom are university graduates. The head office is in Gothenburg and there are regional offices in Lund, Uppsala and Umeå.

www.sik.se