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Now fermenting cacao beans

February 3, 2011

Happy Chinese New Year (February 3rd)!

On June 14, 2010 we had cacao blossom.

On January 5, 2011 we had a lovely yellow cacao fruit ripening.

On February 1, 2011 we picked a cacao fruit from the ground.

As to fermentation, I followed the advice of former Chiang Mai resident Mark Wakefield who has experience from Samoa, and ethnobotanist Nat Bletter from Hawai’i. Nat also referred to a splendid article on cocoa which you can download here!

At this early experimental stage, I simply cut the fruit open. Although it made a nice picture, I think for proper fermentation one should not cut the beans, but peel the fruit and put the beans (embedded in pulp) in a fermentation bowl. I covered the bowl with a glass lid so that I could see what was going on. In this cold season I fear that maybe it is too cold (about 27°C in daytime). One trick worth trying is to add baking yeast, but normally the natural microflora of the pulp should be sufficient.

On February 8, we terminated the fermentation. The suggested time of fermentation is 5-7 days, and since we are in the cold season (this night we had 12.5°C) we made sure we fermented for 7 full days. On day 3 I noticed Rhizopus moulds growing on the surface of the cacao pulp. Since this mould is very common also in soy bean fermentation, I guess it is not dangerous. I mixed the beans with a spoon and added a little bit of water. On day 4 I noted growth of Aspergillus moulds. That could be dangerous, since many of those fungi produce toxins. I guess they initially use the simple sugars in the pulp so there should not be a problem. Still no special fragrance. On day 5 I noticed a fruity alcoholic smell, quite pleasant. I mixed again. On days 6-7 there was a clear smell of baking yeast. Over-fermented cacao beans smell like ammonia, which was not the case here.

Before sun drying I thought I could wash the slimy pulp away, but that was very hard, so today we just put the beans in a plastic basket with a mesh underneath, and let the sun do the job. I removed all beans that had been cut prior to the fermentation. This was a precaution to remove any mouldy cacao bean. This drying procedure should last 7-14 days, the exact time depending on air humidity, after which the beans can be stored for a year. Since our current season is dry I trust seven days will be enough.

Make sure birds and gecko lizards can not leave any droppings, since this is the source of Salmonella now and then reported from governmental chocolate analyses in the west. When I selected the drying spot today I had to consider impressive swarms of palm swifts and barn swallows, glittering green bee-eaters, stout ashy wood-swallows and very high up a noble crested serpent-eagle. I am grateful I do not have more severe problems than keeping aeronauts and chocolate research apart!

On February 11, after three days of sundrying, we had the pleasant surprise of Mark and Fran Wakefield visiting us from Taiwan. As I mentioned above, Mark has a thorough experience from cacao processing in Samoa. He checked the cacao beans and he confirmed what I suspected, the beans were already dry enough. This is ascertained by breaking the beans with your fingers. They will split into dark brown pieces, which taste like dark chocolate and nuts. The relative humidity at Dokmai Garden this time of the year is 37% at 13.00, and 28% at 16.00 before we begin the irrigation of the garden. During irrigation and night, I kept the basket with the beans indoors, protected from gecko lizards by a sheet of paper. In the mornings (08.00), the humidity was 78%. These beans could thus be stored in a dry jar, but I was eager to proceed with the experiments:

On February 13, after five days of drying, I roasted the beans in a gas convection oven at 150°C for 35 minutes. There was a faint fragrance of brownies even with my small batch (36 beans). I first tried the Samoan way of pouring three hot beans into a stone mortar and began pounding. After just three hits I blew away the paper thin seed coats with my mouth and switched to grinding. Due to the heat and the high fat content the beans turned into a paste with the fragrance of black truffles and dark chocolate. I tasted the paste which had a much more pronounced dark chocolate flavour, while the nutty taste of the unroasted beans was reduced. I poured the remaining beans into the mortar and ground it. The seed coats disintegrated into an invisible powder so I should not worry too much about that in the future. In the pdf file mentioned above they recommend using a hair dryer, which is a luxurious step. The amount of cacao paste was 40 ml, equivalent to one cacao fruit.

I transferred 25 ml cacao paste into a 2.5 dl coffee cup, and added boiling water. The flavour was most pleasant, but a bit thin so I added the remaining cacao and stirred for 30 seconds. A lot of the cacao was dissolved, and I could see micelles of cacao fat. The flavour was not a childish cocoa drink which is sweetened milk with a touch of cacao, but a mature flavour of dark chocolate. Ketsanee said it was too bitter, so I added 5 ml of sugar which indeed enhanced the experience.

Next fruit will be used for baking!

Eric Danell

A ripe Forastero cacao fruit from Dokmai Garden, Thailand

The same fruit as above, now cut with a knife. The interior of the cacao beans are purplish with white structures (the embryo). The surrounding white pulp is edible.

The beans and the pulp were transferred to a plastic bowl with a glass lid. Fermentation should take place indoors at (tropical) room temperature. 5-7 days are recommended for Forastero cacao. Turning with a spoon every second day is recommended.

The firm milky pulp from day one has turned slimy and coloured like coffee and cream on day seven.

A cut cacao bean after 7 days of fermentation. The embryo is no longer white, and the original purple has turned more brown (compare with the cut fruit above).

After one hour in the sun, the pulp has shrunken and the cacao beans resemble almonds. There is a clear fragrance of acetic acid, probably as a result of quick oxidation of the alcohol, a byproduct of the yeast fermentation. After three hours in the sun the fragrance resemble an almond you pick up from a hot spiced Swedish mulled wine (glögg)!

A cracked cacao bean after five days of drying.

Roasted cacao in the mortar.

When pounded at room temperature, the texture is more grainy.

Hot homemade cocoa, Samoa style. Aztec style would be with chili.

P.S. I saved one seed (‘bean’) for the next generation. It germinated after 24 days (on February 24th).

4 Comments leave one →
  1. Vasin Tangkaew (วศิน แตงแก้ว) permalink
    February 8, 2011 1:54 PM

    Fantastic experiment. I’m Thai who lived in Chiengmai, but now working in Kalimantan Island, Indonesia. Second from coffee plantation, Cacao tree can be easily seen here as commercial crop for rural people. Can’t wait until the end of your experiment, hope I can do something with abundant local Cacao fruits here.

    Send me your email address, and then I can share you photos of Indonesian Cacao tree & fruit.

  2. September 30, 2014 8:04 AM

    Thanks for finally talking about >Now fermenting cacao beans | Dokmai Dogma <Loved it!


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