The detection and quantification of food components on stainless steel surfaces following use in an operational bakery

Abstract

Food preparation areas in commercial bakeries present surfaces for continual organic fouling. The detection of retained food components and microorganisms on stainless steel surfaces situated for one month in the weighing in area, pastry and confectionary production areas of a bakery were investigated using different methods. Scanning electron microscopy demonstrated the morphology of the material on the surfaces from all three areas, with the weighing in area demonstrating a more even coverage of material. Differential staining assays demonstrated a high percentage coverage of organic material heterogeneously distributed across the surfaces. Differential staining also demonstrated that the amount of organic material on the surface from the confectionary area was significantly greater than from both the pastry and weighing in areas. Although, UV at 353nm did not detect residual surface fouling, performance of the UV detection was optimised and demonstrated that the residual organic material on the weighing in area and the pastry samples was best illuminated at 510–560nm, and from the confectionary area of the bakery at 590–650nm. ATP bioluminescence revealed the confectionary production area contained the highest level of biofouling. Contact plates determined that only low microbial counts (≤2CFU/cm2) were recovered from the surfaces. Changes in the physicochemistry (increased hydrophobicity) demonstrated that all the surfaces were fouled (ΔGiwi −26.8mJ/m2 to −45.4mJ/m2). Fourier Transform Infra-Red Spectroscopy (FTIR) demonstrated that all the surfaces had retained fats, carbohydrates and proteins. This work suggests that a range of methods may be needed to fully detect organic and microbial fouling.