Micro-organisms dominate our planet, they are found in the soil and the oceans, but our knowledge of microbiology is still too limited to human health issues. In this blog, Zarina Mohd, process project manager at IFP looks at biofilms, what implications they can cause and most importantly, how to get rid of them.
There is often a focus on specific micro-organisms in the food production environment when referring to bacterial pathogenic contamination. Foods typically contain a variety of bacteria – some of which may be beneficial, such as products of fermentation, whereas others may be harmful causing foodborne illnesses resulting in product recalls.
Factors that affect the types of bacteria contaminating the food production environment can include their use on different types of raw materials. The environment for growth can vary from one type of bacteria to another, but the majority grow within certain ranges of temperature and specific requirements related to air, water, acid and salt.
Often, low temperatures are used to control the growth of micro-organisms with humidity varying between different types of food processing plants. These are kept dry most of the time. It is important to remember that Micro-organisms can still develop their own micro-environment though, even while the conditions may not be ideal, they still grow. This process is called microbial biofilm and the presence of biofilms in the food production system can be a serious public health risk.
Biofilms are communities of one or more type of micro-organisms, which form gradually over time, starting with attachment of the bacteria to the food product contact surfaces. The purpose of biofilm formation is to protect micro-organisms from hostile environments and to act as a trap for nutrients. Both harmless micro-organisms and harmful pathogenic bacteria can form biofilms and the formation in a food production environment can lead to serious hygienic problems and losses due to food spoilage.
The attachment of bacterial cells depends upon how wet the surface is. Surfaces such as stainless steel and glass generally allow greater bacterial attachment and biofilm formation than surfaces, such as Teflon and fluorinated polymers. Bacteria can also spread within a pipe network and filter, reducing flow and heat transmission. Although the general connotation is negative, biofilms can also be useful in waste-water treatments, for example.
Cross-contamination can also be caused by poor sanitisation on food contact surfaces, equipment and processing environments, which in turn can cause foodborne disease outbreaks. Unfortunately, elimination of biofilms from food processing facilities can be difficult. This is because once a biofilm is formed, bacteria are well protected and although bacteria can be removed using disinfectant, biofilms are more resistant to this conventional anti-microbial method, thus the best strategy is prevention. Disinfecting and deep cleaning before a biofilm develops is the most effective measure, although effectiveness depends on several factors including temperature, concentration and pH and bacterial resistance.
Biofilms can form rapidly in food industry environments, driven by various factors in the manufacturing facility and processing equipment; tanks with pipelines, slicing and cutting equipment, pasteurisers, conveyors, filling and packing machines. Food manufacturers should identify biofilm‐prone areas in their existing process lines and systematically monitor the microbial load in these areas. They need to understand the efficiency of cleaning agents and the decreased sensitivity of biofilm bacteria to certain disinfectants.
The removal of mature biofilm can be done using both mechanical treatment and chemical reagents. Physical treatment such as scrubbing, scraping or spraying can mechanically dislodge biofilms with removal of all layers of bacteria; but the process design can sometimes make the use of mechanical cleaning very difficult, as well as the risk of scratching the surface and leaving behind patches of biofilm that can regrow and re-contaminate.
Chemical use such as peracetic acid which can remove biofilm, but this will depend on food materials in the manufacturing plant, which can dissolve biofilm effectively. A biocide is a chemical treatment that can effectively control microbial growth. Oxidising biocides for example chlorine, chlorine dioxide, hydrogen peroxide, bromine and ozone are typically more effective than non-oxidising biocides which can only treat bacteria and cannot penetrate and remove biofilm.
A final step in the cycle is dispersion which happens when biofilms release and disperse cells into the environment to start another biofilm formation. Toxins can be secreted by biofilm and put human health at risk. Prevention of biofilm dispersion is very important to prevent serious bacterial infection. New technologies are still emerging to prevent biofilm together with established technologies such as plasma treatments, ultrasound, UV light, pulsed electric fields and high-pressure processing. It is critical to control and put a stop to bacterial biofilms since foodborne pathogens are known to be associated with the formation of biofilm in food processing environments.
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