OTA - prevention during processing

During wet processing

• Dispose of pulp from wet processing away from drying or clean coffee. Compost it before using as mulch in the field.
• Pulp on day of picking. Separate floaters and control water quality. Monitor the quality of fresh cherry. What proportion of unpulped cherry and, conversely, nipped/naked beans do you accept? Are skins effectively separated? Ensure these factors are monitored.
• Remove pulp and skins from parchment. Sanitize equipment daily.
• Skin dry wet parchment to remove water quickly. If necessary remove excess water with forced drying. Then dry the parchment slowly to avoid cracking. Turn regularly; do not spread more than 4 cm (1½ inch) thick.
• Remove any pods and skins from the parchment by hand.
• Use drying mats or drying tables where possible. Never dry on bare earth, because mould spores remain in the soil and can cause contamination. Use mats, trays or tarpaulins. Again, raised drying tables, allowing air circulation, remain one of the most effective drying systems.

During dry processing

• Site the dry processing or hulling plant in a dry area, away from swamps.
• Do not buy or process wet coffee. If you must, then keep it separate and dry it immediately and correctly.
• Keep equipment and buildings clean. Do not allow dust and husk to accumulate and so contaminate clean (green) coffee.
• Ensure clean coffee contains no husk: more than 90% of mould originates from the husk of sun-dried cherry. Remove also dust, mouldy beans, unhulled cherries (pods) and so forth.
• Avoid adding husk or pods on purpose (in order to reach a maximum permitted defect level in the specification).
• Use only clean, dry bags for storage. Always keep cleaned coffee in a separate area, well closed off from the hulling area and the waste husk disposal site.
• Ideally moisture content should be even throughout. Use correctly calibrated moisture meters and ensure all meters are recalibrated at the start of each season, preferably more often (!). See also 11.05.05 Preventing condensation.
• The risk of fungi growth is at its strongest when coffee is stored with a moisture content of over 12.5% (ISO 6673) and at high temperatures (over 25°C).
• Cover bags during transport to avoid any chance of rewetting. Load and offload only during dry weather or under cover. Store in well ventilated, leak-proof warehouses. Always store away from walls and on pallets to allow ventilation and avoid storm water damage.

Obvious indicators of potential OTA presence in green coffee include wet or mouldy bags or beans, the presence of husks and pods, an earthy or mouldy smell, and earthy notes in the cup itself. But, OTA has also been found in completely clean coffee.

The ICO agreed method of moisture content analysis is ISO standard 6673: heating at 105 degrees Celsius during 16 hours, or moisture measuring equipment calibrated to the same standard. The sampling method referred to in ISO 6673 is ISO 4072. For details go to www.iso.org.

Websites where information on moisture meters can be obtained include www.sinar.co.uk, http://www.farmcomp.fi/index.php?id=56, www.enercorp.com, www.agric.gov.ab.ca/index.html (search for moisture meters), www.decagon.com/aqualab/ and www.aqua-boy.co.uk.

Readers are strongly recommended to visit www.coffee-ota.org for more extensive coverage on all aspects of the OTA issue. Look under Resources on the same site for presentations and teaching materials on HACCP and the prevention of OTA along the coffee chain, including a CD-ROM version.