3 Pest control and decay
3.1 Pest control
There are not a lot of approved organic post-harvest treatments for pests and diseases. The guidelines usually emphasise the need to minimise pest and disease pressure before harvest. Hot-water (45-55°C) immersion, steam and forced hot-air treatments are sometimes used as organic control methods after harvest. Most pathogenic micro-organisms are destroyed within a few minutes of hot-water immersion. The disadvantages are the risk of product damage: re-humidification of the surface increasing the risk of degradation of the fruit or vegetable; acceleration of ripening; damage to the colour and firmness of the flesh. It is necessary to maintain a very precise temperature (to within a half degree) and treat for a precise time.
For pathogenic micro-organisms, there are antagonistic floras. For example, Bacillus subtilis slows the development of several moulds. In order to be effective, it is necessary that the antagonistic flora are stable, can develop under storage conditions, and are tolerated by the consumer. These techniques are not yet in commercial use for stored fruits and vegetables.
Two additional physical processing methods exist and can be effective but they are not authorized by the legislation on organic agriculture. These methods are microwaves and ionising radiation. Microwaves are a form of electromagnetic energy, transmitted as waves, which penetrates food and once there is converted to heat. The technique is not suitable for fresh produce because the high water content efficiently absorbs microwave energy. Ionisation treatments consist of exposing the fruit or the vegetable to gamma radiation or X-rays. The doses used and permitted on food never render the products radioactive and ionisation does not leave any residues. But public resistance and the high capital cost of an irradiation plant restrict the potential of this technique.