The Detection of Microorganisms and Organic Material on Stainless Steel Food Contact Surfaces

Abstract

Few methods are available for the differentiation of microorganism and organic material on surfaces, although such mixtures are commonplace, particularly in the food industry, where food debris (soil) and microorganisms frequently foul food contact surfaces and pose challenges in terms of hygiene and cleanability. It would be of value to discern any differences in removal or persistence on surfaces. This review considers some methods which are available. Direct epifluorescence microscopy (DEM) enables visual differentiation, but traditional microbiological culture methods cannot detect organic soil. Atomic force microscopy (AFM) provides images of the surface on the nanometer scale, with minimal preparation, and is able to visualise both cellular and acellular components of the mixture, particularly prior to cleaning. Confocal laser scanning microscopy (CLSM) also has potential in this area. Surface sensitive methods such as X-Ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (ToFSIMS) provide information on chemical species present on a surface. Those chemical species more likely on microbial cells may be differentiated from those more likely in a specified organic soil, thus comparisons may be made as to differential removal of the organic soil and microbial cells. These methods may be of value in studies on the fouling and cleanability of surfaces.