Food Protection Trends - November 2008 - (Page 763)

TABLE 2. Biofilm accumulation (log CFU/cm2) on different conveyor belts by L. monocytogenes Belt type Canvas Acetal Polypropylene – Meshtop Polypropylene Stainless steel – Single loop Stainless steel – Balance weave a 2nd Daya 2.11cd ± 0.17 2.76a ± 0.09 2.63ab ± 0.07 2.37bc ± 0.12 1.76e ± 0.06 1.86de ± 0.06 3rd Daya 3.68a ± 0.06 3.67a ± 0.17 3.47ab ± 0.07 3.42ab ± 0.04 3.38ab ± 0.06 3.22b ± 0.11 4th Daya 3.84a ± 0.03 3.79ab ± 0.16 3.64ab ± 0.08 3.64ab ± 0.08 3.44b ± 0.14 3.48ab ± 0.13 Means of triplicate measurements ± standard deviations Within columns, figures that differ significantly (P < 0.05) have different superscripts (canvas) had significantly higher values than the stainless steel single-loop belt test surfaces with no differences among the other belt types. It is important to note that by day 4, even though there were significant differences, all belts supported biofilm growth and accumulation. Therefore, it is important to have a regular and proper cleaning and sanitation program to prevent L. monocytogenes biofilm formation in any belt type. Also, over time (day 2 to 4), L. monocytogenes biofilm accumulation increased in all belts by approximately 1–1.5 log CFU/cm2), indicating that an ineffective cleaning sanitation program will allow biofilms to accumulate on all belt types. Biofilms can grow on both hydrophilic and hydrophobic surfaces, as has been demonstrated by previous research (21, 22, 25, 28). These researchers demonstrated the ability of pathogen to adhere to various surfaces, including polypropylene, rubber, stainless steel, rubber and glass. L. monocytogenes was shown to attach to 17 food-use surfaces in diluted medium at 30oC after a short contact time and to increase in numbers on all surfaces (7). Generally, surfaces that have a greater amount of interconnecting material and have a lower mesh count can be more prone to bacterial attachment. In this study, the polyurethane with mono polyester fabric (canvas) belt that had the lowest mesh (< 1%) had a high L. monocytogenes biofilm attachment when compared to those of higher mesh percentage. The polypropylene belts, that ranged in mesh from 3.2% – 48%, generally showed higher L. monocytogenes numbers than stainless steel. This could be because the stainless steel had a higher mesh percentage that the other belts and therefore had a relatively small area for bacteria to attach. Also, the stainless steel belts have a smoother surface, which is more easily cleanable and which can prevent biofilms from forming. Even though surface area was standardized in this experiment to account for different mesh sizes, the plastic belts had more interlocking parts and smaller mesh sizes for the bacteria to accumulate and grow a L. monocytogenes biofilm. Of significance is that growth of bacteria and development of biofilms will occur on all types of belts if they have not been cleaned and sanitized properly. General sanitation practices include a dry clean step, and use of detergent with hand scrubbing, followed by rinsing, sanitation and air drying. These sanitation steps are critical for prevention of biofilm formation on any surface areas. Therefore, in conclusion, stainless steel belts generally lead to a decrease in L. monocytogenes attachment and biofilm formation (day 2); however, all belts types can have biofilm accumulation over time if they are not properly cleaned and sanitized. a, b, c, d, e RESULTS AND DISCUSSION An especially important and often overlooked consideration in sanitary equipment manufacturing is the design of conveyor belts. Results from this study demonstrate the ability of L. monocytogenes to develop as a biofilm over a 2-day to 4-day time period on food contact materials that are being used in food processing plants. These time points were selected to mimic a long weekend cleaning and sanitizing schedule in a processing plant. Even though 4 days is a long interval between processing and cleanup, improper cleaning and sanitizing can result in development of biofilms. The results from this study comparing different belt surfaces and open mesh structure are indicated in Table 2. Results from analyses of day two L. monocytogenes biofilms indicate that acetal supported a significant accumulation of L. monocytogenes biofilm compared with canvas, polypropylene, stainless steel single-loop and stainless steel–balance weave. The stainless steel single-loop had less biofilm accumulation but was not statistically less than the stainless steel–balance weave. Day three results indicate that the polyurethane with mono polyester fabric (canvas) and the acetal belts had higher L. monocytogenes biofilm accumulation compared with the stainless steel balance-weave belt, which had significantly lower L. monocytogenes biofilm accumulation. By day 4, the polyurethane with mono polyester fabric REFERENCES 1. Allison, D., and I. Sutherland. 1987. The role of exopolysaccharide in adhesion of freshwater bacteria. J. Gen. Microbiol. 133:1319–1327. 2. Anwar, H., J. L. Strap, and J. W. Costerton. 1992. Eradication of NOVEMBER 2008 | FOOD PROTECTION TRENDS 763

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Food Protection Trends - November 2008 Contents Sustaining Members Perspectives from Your President Commentary from the Executive Director Biofilm Formation of Listeria monocytogenes on Various Conveyor Belt Surfaces Third-Party Certification of Agro-Products in China:�A Study of Agro-Product Producers in Guangzhou, Shenzhen, Hangzhou and Qingdao IAFP 2008 in Review Award Winners 3M Microbiology - Black Pearl Award Winner Ivan Parkin Lecture - Russell S. Flowers John H. Silliker Lecture - Michael P. Doyle Student Travel Scholarships Session Summaries Highlights of the Executive Board Meeting Minutes of the 95th Annual Business Meeting Committee Minutes Executive Board Response to Committee Recommendations Exhibitors of IAFP 2008 Special Contributors and Sponsors Call for Awards - IAFP 2009 New Members What's Happening in Food Safety Industry Products Coming Events Advertising Index Journal of Food Protection Table of Contents Audiovisual Library Order Form Booklet Order Form Membership Application

Food Protection Trends - November 2008

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