Frank J M van Esch looks at antibacterial protection for modular conveyor belts which help food manufacturers improve hygiene in the production environment by minimising the cross-infection risks from food poisoning bacteria.
Conveyor belts are one of the prime contact areas for food in the production process, which makes it essential to give priority to proper design. The cleanability of locations which are hard to access, such a s hinge eyes or scratches on the belt surface are critical risk factors in this respect. Despite proper cleaning at the end of the production cycle, there is still a risk that bacteria will develop once again in the subsequent hours.
Conveyor belts with Microban antibacterial protection substantially reduce this risk and provide an improved hygiene level at the start of production. The use of Microban in modular conveyor belts was tested extensively by Rexnord prior to the introduction of the product range.
During a comprehensive test in a production environment with a large bacterial challenge, a direct comparison has been made between a belt with and without Microban. The test was carried out on two identical pork boning lines. Both lines were fitted with MCC2010 conveyor belt, one made of standard acetal and the other made of acetal including Microban.
The over 3000 measurements were taken with so-called contact plates, small securable dishes which contain a culture medium. The dishes are carefully pressed on the belt, thus making a print of the condition of the surface. The dishes are then secured and cultured in a incubator for 24 hours. After that the number of colony forming units (CFU) are counted and the results are categorised in 0 (best) to 4 (worst). Two types of count plates have been used: PCA and VRGB. PCA is a general culture medium, in which virtually all bacteria will grow. A VRGB culture medium is selective for enterobacteriae, such as Salmonella, Staphylococcus, E. coli O157 or Listeria.
Measurements were only taken when the same type of meat was deboned from the same batch on both belts. Measurements were taken before starting production, at the end of production interruptions during the day, half an hour after production and half an hour after the complete cleaning cycle. All measurements were carried out on the positions where the hinge eyes of two consecutive rows are interconnected, using equal numbers of PCA and VRGB contact plates.
Graph 1 shows the difference between the number of CFUs found on the belts with and without Microban antibacterial protection. For this purpose all CFUs of all contact plates have been added. The diagram shows the measurements upon production start-up in the morning as well as the measurements at the end of the production stops. The difference between PCA and the VRGB measurements are also displayed. The absolute numbers found are considered confidential, which is why no values are listed along the linear vertical axis.
Graphs 2a, 2b, 3a and 3b show more detailed results of the measurements. For this purpose, the number of CFU's found per contact plate were classified in five categories, from 0 up to and including 4, as is usual in the meat industry. category 0 shows only few CFUs or none at all, while category 4 is considerably contaminated by CFUs.
The results reflected in the graphs leads to the following: p There is a 90 per cent reduction in the morning measurements of the number of CFUs on belts with Microban, measured by means of PCA contact plates. The morning measurements by means of VRGB contact plates show a reduction of the total number of CFUs by approximately 50 per cent. p The number of CFUs on belts with Microban is also consistently lower at the end of production stops. p Clearly more contact plates were found in category 0 (clean) on the belt with Microban prior to starting production. This applies to both PCA and VRGB contact plates. Fewer contact plates were found in categories 2, 3 and 4. p More contact plates were found in the categories with a lower contamination level on belts with Microban at the end of the production stops: there is a shift to overall average contamination spread.
The general conclusion to be drawn is that the effect of Microban antibacterial protection is not only demonstrable in the laboratory, but also in practice. The effect of antibacterial protection is expected to increase as the belts age and show more wear and tear since this is likely to give better surfaces for bacterial growth.
In view of the results obtained, the Microban antibacterial technology for modular conveyor belts is a very significant complementary benefit, additional to existing good hygienic practices and as such is supportive of best HACCP practice and objectives. It remains important that this should not lead to any deterioration in the cleaning procedures applied. p
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Ir Frank J M van Esch is Food Industry Manager with Rexnord FlatTop Europe, Gravenzande, The Netherlands. www.rexnordmcc.com; www.rexnordmarbett.com; www.rexnordplastics.com
