Development of Microbial Spoilage Test Method: Project Extension to Investigate Additional Test Sites [EXMAW] - Project Update

Note: The following summaries are provided for dissemination purposes to those who may have an interest in the work but not be directly involved in the projects. They may however contain references to other project reports containing full experimental details, access to which is restricted to Industrial Advisory Group Members.

Third Quarter Project Summary for Project DME 4.2

Within the DTI's MDE programme, PRA have been awarded a contract (Project D1) to investigate procedures for improving the qualitative and quantitative test methodology associated with assessment of spoilage to surface coatings by micro-organisms, and in particular by fungi.

Amongst a number of key results obtained from this primary programme it has been shown that both the rate and the ecology of microbial colonisation of exposed coating are sensitive to the location of the field testing sites.

It is proposed that the local microclimate at the different exposure locations is a critical factor in determining the variation in susceptibility to spoilage. As such, the effects of varying local microclimate will need to be taken into account when designing laboratory test procedures, when setting protocols for improvement field trials techniques, and when extrapolating between experimental test results and real-life exposures.

In the ongoing study, under the MDE D 1 programme, exposure sites are limited to three field testing arrays, situated in the South East of England. While sufficient to allow identification of the factors influencing spoilage and to confirm their variability between locations, the restricted geographical distribution of tests sites has limited the conclusions that may be deduced from the data. The awarding of an extension contract (viz DME 4.2) has permitted the design of a programme of investigation covering additional test sites, with more varied and extreme condition of exposure.

In the First Quarter Report (QR 1) of the project work for the extension programme the identification of suitable, additional field sites was made. Two of the proposed sites would cover alpine and tropical climates respectively, while a third offered a UK marine shore environment. A possible further temperature rural site in the UK was identified.

An experimental design, covering the range of substrates, the coating types, and the exposure conditions to be used in the study has been developed (see QR 2). This design covers many of the factors which are being studied in the primary project, and thus the findings of the two projects will have elements that are both supplementary and complementary.

An Industrial Advisory Group (the IAG) has been formed. The work programme presented to their inaugural meeting for advice and approval. The Group has met on two subsequent occasions to review progress.

Methods for intensive monitoring of the weather and microclimate at each site are of paramount importance to the success of the project.. Equipment and techniques for this purpose were developed in the primary project but the new, more remote, locations are presenting new challenges. Details for the construction of the weather monitoring and exposure racking systems for each of the European sites were reported in the Second Quarter Report.

Where remote sites are owned by members of the Industrial Advisory Group, arrangements for the local assessment of spoilage, site management and collection of recordings from the climatic data loggers have been established.

A programme for collecting the field trial data has been drawn up and negotiations with an external consultant, for assistance with statistical design and analysis, and the sub-contractor CABI Bioscience, for ecological and biochemical studies, have taken place to put in place procedures to ensure effective analysis.

The current Quarterly Report update progress for each site. Exposure trials and monitoring at the Alpine site, the Marine site and the additional Rural (UK) site have commenced. Negotiations are underway for the use of a site in the Far East.

By way of additionality to the project, space which has become available at the rural site used in the primary project is being utilised for the exposure of system from the extension project.

A delay in releasing the Third Quarter Report has allowed the inclusion of observations for one month exposure at three of the sites.

Dr R Holman
Project Manager

August 1999

Note: The Funding Programmes "Degradation of Materials in Aggressive Environments" (DME) and "Materials Degradation in Aggressive Environments" (MDE) form parts of the UK Government's, Department of Industry (DTI) support for manufacturing industries.