You are at:

Experimentation on cocoa beans

Experiment 1: Buoyancy tests and observation of the behaviour of cocoa beans

Three hundred containers of coca beans measuring 20 feet and filled 80% full (CMA-CGM information) were onboard the vessel. Upon request from the Préfecture Maritime, Cedre set up an experiment which aimed at finding out about the behaviour of cocoa beans in case the containers fell into the water in the weeks following the incident. A sample of cocoa beans was sent to Cedre in order to study their behaviour in seawater and to be able to answer questions on their floating capacity and the potential risks for the environment.

On 31 October, a sample of beans was placed in a crystallising dish filled with seawater. Nearly all the beans in the sample floated. Only a few beans immediately sank. After soaking in seawater for 40 hours, nearly all the beans were still floating, but were slightly immersed.

 

Experiment 1: Dry cocoa beans immersed in seawater
Experiment 1: Dry cocoa beans immersed in seawater
Experiment 1: Beans immersed in seawater after 40 hours
Experiment 1: Beans immersed in seawater after 40 hours

 

By the third day of immersion of the beans, a great abundance of matter in suspension in the water was observed, and the water had become very turbid. The cocoa beans were sticky to touch, but remained firm. This behaviour could be explained by their high fat content (cocoa butter). On the fourth day, a deposit of matter on the bottom of the beaker was observed. Over time, an increasing proportion of beans sank and a white oily film on the surface indicated the release of lipids. At this stage, there was still no noticeable release of gas, nor any odour of rotting.

 

 Experiment 1: Third day of immersion in seawater
Experiment 1: Third day of immersion in seawater
Experiment 1: Appearance of the cocoa bean after rinsing, after 14 days of immersion in seawater
Experiment 1: Appearance of the cocoa bean after rinsing, after 14 days of immersion in seawater

 

After 14 days, some beans were removed and rinsed. Observation showed that only the protective cuticle around the bean had started to disintegrate; the bean itself still appeared intact.

Experiment 2: Monitoring of gaseous release in an anaerobic environment

In a second experiment, a sample of beans was placed in seawater in anaerobic conditions. A system was set up to recover any gas released.

At the beginning of the experiment, the cocoa beans were all at the surface. As the days went by, the beans began to sink to the bottom of the flask. By the seventh day, many cocoa beans had settled to the bottom, but they could not however be quantified due to the cloudiness of the water, which inhibited visibility.

A release of gas was observed soon after the experiment began. Four days later, the gas was measured using a Draeger tube and the presence of hydrogen sulphide was not detected.

 

Experiment 2 set up to recover the gas released by the beans
Experiment 2 set up to recover the gas released by the beans

 

The quantity of water in the flask gradually decreased and the volume of gas released increased. After 14 days, a foul odour of decay could be detected. From this date the volume of gas released began to decrease.
 After the experiment had run for two and a half months, the presence of hydrogen sulphide was measured again, this time giving a positive indication for the presence of hydrogen sulphide, this gas being generated by the fermentation of the cocoa beans, which had been left in seawater in an anaerobic environment.

Last update: 15/01/2008