Contribution of surface attachment to the establishment of micro‐organisms in food processing plants: A review

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Abstract
Attachment of bacteria to surfaces is a common phenomenon in nature. Bacterial attachment represents an affiliation between the bacterium and the surface. There are three distinct stages in the accumulation of bacteria at a collecting surface viz. (1) adsorption, (2) consolidation and (3) colonisation. In the adsorption of bacteria, physical forces appear to play an important role, and adsorption has been observed for almost all types of surfaces, including food processing equipment. After the initial adsorption, bacteria start to produce extracellular slime and the attachment becomes irreversible (consolidation). Due to the production of slime the properties of the surface change. The slime produced can help the organism to proliferate on the surface (colonisation). Inadvertent spreading of colonies in machinery e.g. by mechanical means, will inevitably lead to colonisation of fresh surfaces. The biofouling of surfaces can readily be observed by scanning electron microscopy (SEM). Especially, the microtopography of the collecting surface can be made visible by SEM. Surfaces like rubber, aluminium, factory floors and stainless steel possess deep channels and crevices which trap bacteria. Many problems arise as a result of bacterial attachment to processing equipment, such as reduction of the efficiency of operation and stimulation of the corrosion process. From a hygiene point of view, however, the most important problem that arises from surface biofouling is the continuous contamination of food being processed. In this paper different aspects of bacterial attachment are described and the practical consequences are emphasized.