Defining and managing risks to safety and quality during food and feed grain storage

Abstract

A key area of importance in protecting the grain supply chain from farm to consumer is good grain storage. Hazards in grain storage include fungi that can produce mycotoxins, and stored product insects and mites. All of these have the potential to reduce quality below acceptable standards for food hygiene. The overall objective of this project was to establish best practice for the UK storage industry, based on a hazard analysis and critical control point (HACCP) approach, to identify and prevent or control the risks associated with grain storage.

Key findings from the project are:

• Penicillium verrucosum is found frequently in UK grain stores. Conveyer systems and combine harvesters may harbour high levels of Penicillium verrucosum.
• Hygiene measures, in general, reduce the amount of inoculum present.
• Penicillium verrucosum is able to develop in the upper grain surface in the winter months, but a broader survey is required to determine the extent of this.
• Resistance to pirimiphos-methyl in Oryzaephilus surinamensis and Acarus siro populations is widespread. For O. surinamensis this may not result in a control failure, but control failure is possible for A. siro populations. Maintaining the correct physical conditions in the store is therefore important.
• Population growth models have been produced for two insect species on wheat and barley and three mite species on wheat, barley and oilseed rape. These models are likely to be the best that are currently available.
• The setting of the differential thermostat was the most important element in determining whether cooling was successful and for how many hours the fan had to be run. A 3°C diffstat setting was significantly more successful than a setting of 5°C. The current airflow recommended for cooling, 10 m³/(h.tonne wet matter), was found to be optimal for cooling.
• Interpretation of insect trap catch is a very difficult area and complex models would be needed to fully elucidate this. However, the findings reinforced the need for monitoring for insect presence both at the surface and just below the surface.
• The ability of insects and mites to vector P. verrucosum illustrates the interactions between the various hazards likely to be encountered in UK stores and the importance of monitoring and establishing thresholds for control actions to reduce the risk.

The findings from this project and the HACCP approach developed were used for the production of the third edition of the HGCA Grain storage guide. The new guide, based on an HACCP approach, was launched in October 2011.