Hermetic Storage: a Novel Approach to the Protection of Cocoa Beans

Hermetic storage has provided a successful storage method for protection of commodities without fumigants or need for refrigeration for insect control and quality preservation of stored products. Hermetic storage is achieved in specially constructed plastic structures for the preservation of cereal grains and other commodities. Plastic structures suitable for long-term storage systems, as well as intermediate storage of grain have been developed and applied. These storage systems based on the hermetic principle were designed for (1) storage at the farmercooperative and small trader level with 10 1000 tonnes capacity for enclosing stacks termed CocoonsTM, (2) small scale storage suitable for small portable containers of 60 kg to 2 tonnes called SuperGrainbagsTM and (3) quality preservation, insect control and prevention of condensation during shipment of commodities in shipping containers known as TranSafelinersTM. Hermetic storage is based on the principle of generation of an oxygendepleted, carbon dioxide-enriched interstitial atmosphere caused by the respiration of the living organisms in the ecological system of a sealed storage. A sufficiently low oxygen and elevated CO2, atmosphere is created through a natural metabolic process based on insect respiration and, in cases where the commodity has sufficiently high moisture, the respiration of the microorganisms within a sealed storage system. Applications for which hermetic technology has been most widely accepted are long-term storage of cereal grains, primarily rice, corn, barley, wheat and a variety of seeds to preserve germination potential and vigor and quality preservation of high-value commodities such as cocoa and coffee. Under field conditions in a cocoa bean storage facility in Makassar, Indonesia, a hermetically sealed flexible structure containing 6.7 tonnes of cocoa beans at an initial moisture content of 7.3% and relative humidity of 70% was monitored for oxygen concentration and quality parameters of the beans. The measurements showed a decrease in oxygen concentration to 0.3% after 5.5 days. No insects survived the oxygen depleted biogenerated atmosphere. Similar trials were carried out in Ghana by COCOBOD in which three stacks for hermetic storage and one stack each for conventional storage (without fumigation) and standard storage (with fumigation) were built for sampling and observation. At the sixth week of storage 100% mortality of insects was recorded in the CocoonTM. All the cocoa beans inside the CocoonTM maintained their quality category throughout the storage period and the grade remained the same after nine weeks of storage as it was at the beginning of the experiment.