Jenni Määttä

Microbiological Quality of Fresh-Cut Carrots and Process Waters

Fresh vegetables may be contaminated by pathogens in different ways after harvest. Pathogenic microorganisms associated with fresh vegetables can cause severe outbreaks of foodborne disease. We discuss here the results of microbiological analysis of carrot samples, as well as of washing, processing, and wastewater samples. Washed, unpeeled carrots generally contained the highest aerobic plate counts (mean, 5.5 log CFU/g). Escherichia coli was not detected in any carrot or water sample examined. The amounts of coliform bacteria and enterobacteria were higher in carrot samples taken from the first steps in the processing line than in samples taken in later phases of the process. Yersinia pseudotuberculosis was not detected in any of the samples by the cultivation method; however, nonpathogenic Yersinia enterocolitica was detected from most carrot samples and almost all washing water and wastewater samples but only from 2 of 10 process water samples. Using a more-sensitive real-time PCR method, pathogenic Y. enterocolitica was found from several carrot samples, and when these positive samples were cultivated, no pathogenic Y. enterocolitica strains were detected.

Application of radiochemical determination methods in cleanability research of building materials

During recent years increasing effort has been made to modify surface properties with easy-to-clean or self-cleaning characteristics, and concomitantly there is a need to be able to quantify cleanability. Methodology is a complex issue, including aspects of selection and characterization of the surface materials, the soiling materials (contaminants), soiling and cleaning methods, and the detection methods. Different biological, chemical, physical and visual methods have been included in studies of surface cleanability. One challenge has been to obtain quantitative information about soiling. The radiochemical methods, gamma spectrometry (NaI(Tl)-crystal) and liquid scintillation counting, have been shown to be suitable for evaluating cleanability of different surface materials and different soiling material types, providing quantitative information about the amount of soiling material both on and beneath the surface. Due to the different labelled soiling components, the interaction of the surface with different soiling material types can be evaluated. Radiochemical methods have unique benefits particularly for examining porous materials and surfaces. However, they are suitable only for highly controlled studies because of the hazards. Different features and details of radiochemical methods are discussed with the view to aid planning of future cleanability studies.

Evaluation of different floor materials in cattle barns.

Floor surfaces in livestock barns are of special interest, since they should withstand strong mechanical and chemical stress and they should also be as comfortable as possible to stand and lie on. Furthermore, the floors should be easy to clean. The aim of this project was to develop well-functioning floor surface materials for use in animal houses. Both laboratory and field tests were performed. Changes in repellence and surface properties, cleanability, colour and gloss of materials were measured. Materials for the field test were chosen according to the results of laboratory studies with the exception of silane-impregnated concrete. The other materials selected were epoxy-, polyurethane- and acrylic coatings for floorings and feeding tables, and polyester coating for feeding tables. Two materials not tested in the laboratory were also included in the field tests. Traditional concrete was used as reference. The surface materials had more effect on changes in cleanability and repellence of tested materials than the chemical stresses introduced. SEM pictures showed that during wear the surfaces became rougher or scratches appeared on them. According to profilometer measurements no significant differences between the changes in the surface roughness of test materials were observed. The results of colour and gloss measurements varied considerably, but in general, coating decreased the changes of colour and gloss of the surface materials. The field study provides practical information about the behaviour of the surface materials examined.