Discover Chocolate and Live La Vida Cocoa!
Cocoa Fermentation 101
Prior to being dried, cacao seeds (or "cocoa beans") are fermented ... or, more accurately, the fruity pulp which envelops the beans is fermented.
The fermentation process liquefies the pulp, allowing it to drain away. This reduction in pulp assists the drying process. But most importantly, cocoa fermentation triggers an array of chemical changes within the bean. These chemical changes are vital to the development of the complex (and much-loved) flavour known as "chocolate".
Prior to fermentation, the ripe cacao fruits (known as pods) are carefully cut from the tree. The harvested pods are taken to a central location, where the fermentation will take place. Some growers ferment their own beans in relatively small heaps on the floor of the plantation, while others take their pods to a co-op for larger-scale box fermentation. But regardless of the scale of the operation, the fermentation process is essentially the same.
When the pods have been gathered at the fermentary, they are broken open, and the beans are scooped out.
For as long as a cacao pod remains intact, it is sterile, meaning that it contains no yeasts or bacteria. However, during the pod-breaking and bean-scooping stage, the pulp is inoculated with wild yeasts and bacteria. Scientists believe that the bulk of these microogranisms are transferred from the skins of the pods to the beans, via the bean-scoopers' hands.
In the first stage of fermentation, the wild yeasts rapidly multiply in the sweet, fruity pulp, converting the pulp's sugar into alcohol. This initial phase takes place in the absence of oxygen - hence, it is known as anaerobic fermentation. The yeast population peaks within 24 hours.
After the yeasts have done their work, bacteria begin to take over the fermentation process, converting the alcohol into acid. This acid slowly penetrates the bean.
The bacterial phase of fermentation takes place in the presence of oxygen - hence, it is known as aerobic fermentation. This phase requires a significant amount of oxygen, so the beans are typically turned at least twice during the fermentation process, in order to introduce oxygen into the heap, and to ensure that all of the beans are fermented evenly. Typically, the beans are turned at about 48 and 72 hours after fermentation begins.
The bacteria population peaks roughly 72 hours after fermentation first begins, and decreases rapidly over the following 72 hours. Hence, the entire fermentation process typically takes about 144 hours (six days).
=====
Phase 1 of cocoa fermentation (anaerobic): sugar + yeast --> alcohol + carbon dioxide + heat
Phase 2 of cocoa fermentation (aerobic): alcohol + bacteria + oxygen --> acid + water + heat
=====
As well as producing alcohol and acid, the fermentation process also generates heat, typically raising the temperature of the fermenting beans to about 45 to 50 degrees Celsius (113 to 122 Fahrenheit).
The acid and heat generated by the fermentation kills the cocoa bean. In turn, the bean's death causes cell walls within the bean to break down, allowing enzymes to come into contact with their substrates. These enzymes bring about some very important chemical changes within the bean, some of which are listed under points 2 and 3, below.
=====
Enzyme: a protein that induces chemical changes in other substances. The substance that an enzyme changes is known generically as a substrate.
=====
Very broadly speaking, three major changes happen inside the cocoa bean during fermentation:
1. Acid penetrates the bean. The acid kills the bean, lowers its pH, and produces a sour, acidic taste.
2. Bitter and astringent flavonoids are converted into milder-tasting substances.
3. Aroma precursors are produced. These aroma precursors are transformed into aromas during roasting.
Below I explain these three major changes in a bit more detail:
1. Acid penetrates the bean.
As previously mentioned, some of the acid which is produced by bacteria during the second phase of fermentation penetrates the bean. This acid is primarily acetic acid: the same acid that gives vinegar its sour taste. Most of this acid is later evaporated out of the bean, during drying and conching. However, a moderate amount of residual acidity can lend a desirable, fruity complexity to cocoa.
2. Bitter and astringent flavonoids are converted into milder-tasting substances.
Freshly harvested cocoa beans are extremely bitter, astringent, and unpalatable. This unpleasant bitterness is primarily due to high levels of water-soluble flavonoids (a.k.a antioxidants) in the bean. During fermentation, these flavonoids undergo a complex series of chemical transformations. For example:
* Some flavonoids combine with other flavonoids to produce larger molecules known as condensed tannins, or proanthocyanidins. This process is very similar to the mellowing process that fine red wine undergoes as it ages. Incidentally, proanthocyanidins are a category of antioxidants that are widely believed to be very good for you (this is why the media often hypes chocolate as a "health food").
* In a multi-step process, some flavonoids oxidise and condense, producing the classic chocolate brown pigmentation in cocoa. This process is known generically as enzymatic browning.
During cocoa fermentation, flavonoids combine with eachother, and with proteins and amino acids, in myriad ways - not all of which are perfectly understood by science. For example:
anthocyanin [purple] + glucosidase enzymes --> anthocyanidin [purple] + sugar
anthocyanidin [purple] + polyphenol oxidase enzymes + oxygen --> quinone [yellow]
quinones [yellow] + other flavonoids + amino acids --> condensed tannins
condensed tannins + proteins --> melanin [brown, water insoluble pigment]
Notes regarding the colour of the cocoa bean:
* Freshly harvested cocoa beans range in colour from white to dark purple.
* If the flesh of an unroasted cocoa bean is brown, then it has undergone enzymatic browning.
* If cocoa beans are dried without first being fermented, they become a slaty grey colour.
So-called slaty beans are considered to be defective under international standards.
* Under-fermented beans remain bright purple. Purple beans are much more bitter and astringent, and have fewer aroma precursors, than fully fermented beans.
3. Aroma precursor development.
Freshly harvested cocoa beans taste nothing like chocolate. The bulk of the chocolate flavour-production happens during roasting, when a chemical reaction known as the Maillard reaction takes place. (The Maillard reaction is sometimes confused with caramelization).
The Maillard reaction is a reaction between so-called "aroma precursors" - namely, amino acids and reducing sugars. When cocoa is roasted, the aroma precursors combine in different ways to create dozens of different flavor compounds.
These all-important aroma precursors are produced during fermentation as a result of enzyme activity. For example:
* Protease enzymes break proteins down into peptides and amino acids.
* Invertase enzymes break sucrose down into fructose and glucose. Fructose and glucose are known as "reducing sugars"
=====
After fermentation, the cocoa beans are dried. Drying reduces the moisture content in the bean from about 55% to about 7%. With a moisture content of 7%, cocoa beans can keep for many years (in ideal storage conditions).
=====
REFERENCES:
Camu, N.; Gonzalez, A.; De Winter, T.; Van Schoor, A.; De Bruyne, K.; Vandamme, P.; Takrama, J.S.; Addo, S.K.; De Vuyst, L. (2008)
"Influence of Turning and Environmental Contamination on the Dynamics of Populations of Lactic Acid and Acetic Acid Bacteria Involved in Spontaneous Cocoa Bean Heap Fermentation in Ghana"
Applied and Environmental Microbiology, Vol. 74, No. 1, pp. 86-98
Hansen, C.E.; del Olmo, M.; Burri, C. (1998)
"Enzyme activities in cocoa beans during fermentation"
Journal of the Science of Food and Agriculture, Vol. 77, Issue 2, pp.273-281
Schwan, R.F.; (1998)
"Cocoa Fermentations Conducted with a Defined Microbial Cocktail Inoculum"
Applied and Environmental Microbiology, Vol.64 Issue 4, pp.1477-1483
The fermentation process liquefies the pulp, allowing it to drain away. This reduction in pulp assists the drying process. But most importantly, cocoa fermentation triggers an array of chemical changes within the bean. These chemical changes are vital to the development of the complex (and much-loved) flavour known as "chocolate".
Prior to fermentation, the ripe cacao fruits (known as pods) are carefully cut from the tree. The harvested pods are taken to a central location, where the fermentation will take place. Some growers ferment their own beans in relatively small heaps on the floor of the plantation, while others take their pods to a co-op for larger-scale box fermentation. But regardless of the scale of the operation, the fermentation process is essentially the same.
When the pods have been gathered at the fermentary, they are broken open, and the beans are scooped out.
For as long as a cacao pod remains intact, it is sterile, meaning that it contains no yeasts or bacteria. However, during the pod-breaking and bean-scooping stage, the pulp is inoculated with wild yeasts and bacteria. Scientists believe that the bulk of these microogranisms are transferred from the skins of the pods to the beans, via the bean-scoopers' hands.
In the first stage of fermentation, the wild yeasts rapidly multiply in the sweet, fruity pulp, converting the pulp's sugar into alcohol. This initial phase takes place in the absence of oxygen - hence, it is known as anaerobic fermentation. The yeast population peaks within 24 hours.
After the yeasts have done their work, bacteria begin to take over the fermentation process, converting the alcohol into acid. This acid slowly penetrates the bean.
The bacterial phase of fermentation takes place in the presence of oxygen - hence, it is known as aerobic fermentation. This phase requires a significant amount of oxygen, so the beans are typically turned at least twice during the fermentation process, in order to introduce oxygen into the heap, and to ensure that all of the beans are fermented evenly. Typically, the beans are turned at about 48 and 72 hours after fermentation begins.
The bacteria population peaks roughly 72 hours after fermentation first begins, and decreases rapidly over the following 72 hours. Hence, the entire fermentation process typically takes about 144 hours (six days).
=====
Phase 1 of cocoa fermentation (anaerobic): sugar + yeast --> alcohol + carbon dioxide + heat
Phase 2 of cocoa fermentation (aerobic): alcohol + bacteria + oxygen --> acid + water + heat
=====
As well as producing alcohol and acid, the fermentation process also generates heat, typically raising the temperature of the fermenting beans to about 45 to 50 degrees Celsius (113 to 122 Fahrenheit).
The acid and heat generated by the fermentation kills the cocoa bean. In turn, the bean's death causes cell walls within the bean to break down, allowing enzymes to come into contact with their substrates. These enzymes bring about some very important chemical changes within the bean, some of which are listed under points 2 and 3, below.
=====
Enzyme: a protein that induces chemical changes in other substances. The substance that an enzyme changes is known generically as a substrate.
=====
Very broadly speaking, three major changes happen inside the cocoa bean during fermentation:
1. Acid penetrates the bean. The acid kills the bean, lowers its pH, and produces a sour, acidic taste.
2. Bitter and astringent flavonoids are converted into milder-tasting substances.
3. Aroma precursors are produced. These aroma precursors are transformed into aromas during roasting.
Below I explain these three major changes in a bit more detail:
1. Acid penetrates the bean.
As previously mentioned, some of the acid which is produced by bacteria during the second phase of fermentation penetrates the bean. This acid is primarily acetic acid: the same acid that gives vinegar its sour taste. Most of this acid is later evaporated out of the bean, during drying and conching. However, a moderate amount of residual acidity can lend a desirable, fruity complexity to cocoa.
2. Bitter and astringent flavonoids are converted into milder-tasting substances.
Freshly harvested cocoa beans are extremely bitter, astringent, and unpalatable. This unpleasant bitterness is primarily due to high levels of water-soluble flavonoids (a.k.a antioxidants) in the bean. During fermentation, these flavonoids undergo a complex series of chemical transformations. For example:
* Some flavonoids combine with other flavonoids to produce larger molecules known as condensed tannins, or proanthocyanidins. This process is very similar to the mellowing process that fine red wine undergoes as it ages. Incidentally, proanthocyanidins are a category of antioxidants that are widely believed to be very good for you (this is why the media often hypes chocolate as a "health food").
* In a multi-step process, some flavonoids oxidise and condense, producing the classic chocolate brown pigmentation in cocoa. This process is known generically as enzymatic browning.
During cocoa fermentation, flavonoids combine with eachother, and with proteins and amino acids, in myriad ways - not all of which are perfectly understood by science. For example:
anthocyanin [purple] + glucosidase enzymes --> anthocyanidin [purple] + sugar
anthocyanidin [purple] + polyphenol oxidase enzymes + oxygen --> quinone [yellow]
quinones [yellow] + other flavonoids + amino acids --> condensed tannins
condensed tannins + proteins --> melanin [brown, water insoluble pigment]
Notes regarding the colour of the cocoa bean:
* Freshly harvested cocoa beans range in colour from white to dark purple.
* If the flesh of an unroasted cocoa bean is brown, then it has undergone enzymatic browning.
* If cocoa beans are dried without first being fermented, they become a slaty grey colour.
So-called slaty beans are considered to be defective under international standards.
* Under-fermented beans remain bright purple. Purple beans are much more bitter and astringent, and have fewer aroma precursors, than fully fermented beans.
3. Aroma precursor development.
Freshly harvested cocoa beans taste nothing like chocolate. The bulk of the chocolate flavour-production happens during roasting, when a chemical reaction known as the Maillard reaction takes place. (The Maillard reaction is sometimes confused with caramelization).
The Maillard reaction is a reaction between so-called "aroma precursors" - namely, amino acids and reducing sugars. When cocoa is roasted, the aroma precursors combine in different ways to create dozens of different flavor compounds.
These all-important aroma precursors are produced during fermentation as a result of enzyme activity. For example:
* Protease enzymes break proteins down into peptides and amino acids.
* Invertase enzymes break sucrose down into fructose and glucose. Fructose and glucose are known as "reducing sugars"
=====
After fermentation, the cocoa beans are dried. Drying reduces the moisture content in the bean from about 55% to about 7%. With a moisture content of 7%, cocoa beans can keep for many years (in ideal storage conditions).
=====
REFERENCES:
Camu, N.; Gonzalez, A.; De Winter, T.; Van Schoor, A.; De Bruyne, K.; Vandamme, P.; Takrama, J.S.; Addo, S.K.; De Vuyst, L. (2008)
"Influence of Turning and Environmental Contamination on the Dynamics of Populations of Lactic Acid and Acetic Acid Bacteria Involved in Spontaneous Cocoa Bean Heap Fermentation in Ghana"
Applied and Environmental Microbiology, Vol. 74, No. 1, pp. 86-98
Hansen, C.E.; del Olmo, M.; Burri, C. (1998)
"Enzyme activities in cocoa beans during fermentation"
Journal of the Science of Food and Agriculture, Vol. 77, Issue 2, pp.273-281
Schwan, R.F.; (1998)
"Cocoa Fermentations Conducted with a Defined Microbial Cocktail Inoculum"
Applied and Environmental Microbiology, Vol.64 Issue 4, pp.1477-1483
Comment
-
Comment by Donald Deosaran on November 7, 2009 at 12:32pm - An excellent post, your explanation of why it is necessary to turn the beans after 2 days was insightful, since it is done on our estate, but the reasoning for it was not fully known from a scientific point of view, i.e. for aerobic fermentation.
-
Comment by Patricia S Verdesoto Estévez on October 17, 2009 at 10:03pm -
Sorry for my writing errors, the correct word is "cocoa quality". Better, standard of fine/aroma cocoa (criollo variety).
Patty
-
Comment by Patricia S Verdesoto Estévez on October 17, 2009 at 9:59pm
-
Hi, when I found this page I was to happy because I am looking for cocoa properties and the specific reasons of the chocolate´s flavor and aroma. I need this information because I am working in my final project to get my B. Sc. degree and this information is very clear and specific. Thanks to share this Samantha. Finally, I like to share something about my job. I made chemical analysis of 9 samples of cocoa (pH, total fat, protein, sugar reductors, raw fiber, phenols, tannins, theobromine, caffeine, palmitic, oleic and estearic acid) and I need to know if there is a standard that shows what are the values of this components in a fine cocoa in order to compare. With this comparation I could made conclusions about what is the cuallity of my samples. Please if you know where or how I can get this information, help me please. I have some information about this, however I need reliable information.
take care!!
Patty
-
Comment by Samantha Madell on May 19, 2009 at 7:31pm -
Hi Donna,
I'm really pleased that you found this post useful.
In answer to your question about fermenting 20 pods' worth of cocoa:
Twenty pods will give you roughly 2kg of fresh beans and pulp ... that's a very small amount to ferment (the smallest fermentation pile I've seen was about ten times that size). However, it can't hurt to try. Just make sure that the beans don't dry out before they get the chance to ferment, and please let us know how you go!
And regarding the question of why Balinese growers don't ferment their beans ... if you're in Bali, maybe you could ask some growers why they don't ferment, and let us know. That would be great!
-
Comment by Donna on May 16, 2009 at 9:40pm
- HI Samantha: Great article, thanks so much for the information. I for one am hoping to use your information to do my own pile of fermented beans. Right now I only have about 20 ripe pods, do you think that's enough to ferment? Here in Bali the farmers don't ferment, but in Sulawesi they do. Could it be that the beans in Bali are used for cocoa butter instead of chocolate?
-
Comment by Samantha Madell on May 14, 2009 at 8:21pm
-
Hi Clive,
Thanks for the feedback!
In answer to your question about reasons for not fermenting cocoa: at the risk of sounding flippant, I would say that growers who don't ferment their beans simply have no good reason to do so. If whoever buys the beans doesn't demand (or reward) proper fermentation, then why bother?
Also, in countries where there is no tradition of making or consuming chocolate, then fermentation is not really an obvious step.
The kind of people who hang out at The Chocolate Life really care a lot about flavour - but the same can't be said for the majority of the general population. For example, I know more than one person who is utterly convinced that Dutched (alkalized) cocoa has a richer flavour, simply because it has a rich, dark colour.
Also, a fact that many chocolate enthusiasts are unaware of is that about two-thirds of the world's annual cocoa crop gets turned into cocoa butter and cocoa powder.
Fermentation doesn't affect the quality of cocoa butter, but as for the cocoa powder ... if you've ever tasted a generic supermarket brand of cocoa powder, you'll know how awful the stuff is.
Furthermore, the world's most popular chocolate products (I'm thinking of products like Mars Bars and Cadbury Dairy Milk) tend to contain truly minuscule amounts of non-fat cocoa solids - in other words, most so-called "chocolate" isn't very chocolatey at all. It's all about sweetness and texture and colour.
But, just to confuse matters, there's also the fact that even unfermented cocoa can produce some chocolatey flavour when roasted. This issue was raised by Clay, over in the thread Shattering Preconceptions: How Chocolate Really Gets Its Flavor
Clay wrote:
"My epiphany was that fermentation is not necessary for the development of chocolate flavor in chocolate [...]. The demonstration of a traditional Mayan technique for making cocoa water was what showed me this. Farmer Eladio Pop does not ferment the beans his family uses to make cocoa water because it's too much work. Instead, the beans are washed free of pulp and dried. These beans are then roasted on a comal (a traditional flat metal griddle) over an open wood fire, cracked, winnowed, and then ground (using a hand corn mill) into a paste with black pepper and other spices (especially local allspice).
[...] Even without fermentation the cocoa water had a very strong chocolate taste with the flavors of roasting and a strong nut (reminiscent to me of cashews) flavor."
-
Comment by Clive Brown on May 11, 2009 at 7:37pm
- Samantha, great info. Obviously there is huge importance in the fermentation process. Why is then that some places worldwide choose just to dry their beans before roasting? ( I noticed this in Bali. There have been other posts on this site mentioning buying unfermented beans in Central America). Obviously, one less stage in the bean to bar process involves less work, but how can anyone get away without fermentation when it is so critical to taste?
-
Comment by Samantha Madell on March 2, 2009 at 9:33pm
-
Hi Jim,
Thanks for your detailed and thoughtful response.
I totally agree with the emphasis you place on the importance of post harvest processing. And I accept that you find my idea of a "general rule" for fermentation irritating. Nevertheless, I stand by what I wrote -- for example, please note that my "general rule" includes observing the beans daily, and taking appropriate action as necessary. I was certainly not trying to imply that correct fermentation requires no skill, experience, or care on the part of the person controlling the fermentation.
I wrote my original blog post with the intention of giving chocolate enthusiasts some insight into the basic chemistry of cocoa fermentation and chocolate flavour development. I wasn't anticipating that this page would be used as an instruction manual for cocoa growers who aren't familiar with the widely-accepted basics of cocoa fermentation.
For example, my original post was based on a number of very basic assumptions that I did not mention. In retrospect, I probably should have listed these assumptions at the outset, but as I mentioned above, my original post was aimed at chocolate consumers, not cocoa growers.
In response to your list of variables, my basic assumptions are:
1. The cocoa beans to be fermented are ripe.
2. The fermentation is taking place somewhere within cacao's normal or optimum growing area -- in other words, at low altitude within the humid tropics, where the ambient temperature does not adversely affect fermentation. (On this point, I'm working from personal observations on 3 different continents, as well as data obtained from numerous relevant books).
3. The beans are removed from the placenta (which helps prevent clumping), but are not washed.
4. The fermenting beans have adequate drainage to allow the fermentation's liquid by-products (alcohol, acid, and water) to drain away. Based on personal observations, effective drainage can be achieved regardless of whether the beans are fermenting in a box, or in a pile on the floor of the plantation.
5. The beans are fermented in a pile large enough for fermentation (rather than drying) to take place. In my personal experience, the fermenting pile can be much smaller than commonly accepted. For example, I've seen perfect fermentation take place in a pile of beans weighing only about 20kg. At the other extreme, I make the assumption that no grower would make a pile of beans so large that he can't manage it, however it is not unusual for fermentation boxes with a capacity of roughly half a tonne to be used.
6. As explained in my original post, the fermenting beans are turned at 48 and 72 hours. Many different turning regimes can be followed, but this regime will give a good result, without being too onerous.
7. The fermenting beans are covered. (I've seen successful fermentation carried out with cover materials ranging from banana leaves to hessian sacks).
8. As mentioned in my previous comment, the beans are inspected daily, and appropriate action is taken if necessary. It is not necessary to measure the temperature of the fermenting beans - if all of the guidelines and assumptions I've mentioned are followed, then nature will take its course.
On this point, I would like to mention the superb results obtained by cocoa growers we visited in a very remote village in Vanuatu. These growers have no books, fermentation boxes, or thermometers. They have no knowledge of chemistry, and many of them have probably never tasted chocolate - yet they produce perfectly fermented cocoa beans every time.
They achieve this result by consistently following a series of fairly simple procedures, as taught to them by their fathers. In turn, their fathers were (according to the growers we spoke to) taught these procedures by a visiting official at some time in the 1980s.
-
Comment by Jim on March 2, 2009 at 6:22pm -
Samantha,
As always your comments were well prepared and beneficial to all that are involved in post harvest processing.
I take exception to "the general rule of ...6 days" to complete fermentation. It has been our experience that fermentation of cacau depends on many variables and "general rules" do not create quality cacau. I seriously doubt that fermentation processes as depicted in the recent banana leaf pile photo and those occurring in a wooden, indoor, 1 cubic meter fermentation vat are equal. Our processes are exclusively controlled by observation of the individual fermentation piles.
Some of the fermentation variables that I've observed are:
1. The state of fruit ripeness when induced into the pile
2. Ambient temperature and humidity
3. Pre- fermentation procedures (cleaning, individual bean separation, etc.)
4. Rate of drippings drainage
5. Dimension of pile
6. Frequency of bean position rotation
7. Use or not of pile cover
8. Physical analysis of the bean fermentation process ( temperature, color, smell, etc)
It would be remiss to accept the premise that time is the measure of quality fermentation. To often, technical documents are produced that although correct, are only correct within a particular set of parameters. It is true that fermentation processes are "normally" complete within the stipulated 6-7 day period. The fact remains that time is not an acceptable unit of measure when describing cacau fermentation.
To often we are bombarded with the marketing jargon of ….”cacau produced under the shade of”…. “grown in the pristine forest of….”, "purchased from the co-operative of” and forget that post harvest process of cacau is equally important to that of chocolate alchemy. The worlds finest chocolate masters are unable to produce fine chocolate with poor quality beans. The ability to control post harvest processes with guaranteed repeatability is an absolute requirement for producers. Anything less is “Marketeering Hype”.
-
Comment by Samantha Madell on March 1, 2009 at 6:58pm
-
Jo, Jim, and Subhashini - thank you for your wonderful feedback!
To answer your questions:
Jim - please feel free to use this information for your Quality Control procedures documentation.
Subhashini - I don't have any first-hand experience in judging exactly when to halt fermentation, but you might find the following information useful ...
Judging the correct degree of fermentation by colour
Cocoa buyers assess the degree of fermentation in cocoa by performing a cut-test on a random sample of fermented and dried beans:
If the cotyledons are slaty grey, then the bean is totally unfermented.
If the cotyledons are completely or partially purple, then the bean is under-fermented.
If the cotyledons are completely brown, then the bean is fully fermented.
=====
Cotyledon: also known as a "seed leaf", a cotyledon is an embryonic leaf. In cacao (and many other plant species) the cotyledons become the first green leaves after germination. Cacao is a dicotyledon, meaning that each seed contains two cotyledons.
Chocolate Life member, Koa Kahili, has posted an excellent photo of partially green cacao cotyledons here
=====
From a grower's point of view, the cut-test is not a perfect guide to fermentation, because the effects of fermentation can continue during drying. (This happens because the polyphenol oxidase enzymes that are responsible for browning the cotyledons during fermentation remain minimally active during drying).
On the subject of judging the end-point of fermentation by using a cut-test, Wood & Lass [1] write:
"After the death of the [Forastero] bean, the space within the bean becomes filled with an exudate of a violet colour, and this, together with the cotyledons and radicle, turns brown rapidly when the bean is cut open. At a later stage, the exudate becomes a reddish brown and the cotyledons become paler in the centre with a brownish ring around the outside. Such beans have been adequately fermented and are ready for drying." (p.471)
Avoiding over-fermentation
As mentioned in my original blog post, the beneficial bacteria population in a pile of fermenting cocoa beans decreases to zero at about 144 hours (or 6 days) after fermentation begins. When the population of fermenting microorganisms reaches zero, then no further fermentation can possibly take place. Hence, there is no obvious reason to "ferment" any variety of cocoa for more than 6 days.
This conclusion is supported by Wood & Lass [1], who note that, after six or seven days of fermentation, some of the cocoa beans (especially those in the corners of fermentation boxes) become "nearly black, and such beans will have an unpleasant ammoniacal smell. This marks the onset of changes associated with over-fermentation and when this smell appears, the fermentation should be brought to an end and drying started." (p.470, Cocoa, 4th edition).
What is the optimum duration for cocoa fermentation?
One scientific study in Sri Lanka [2], which was carried out using three different cocoa varieties, concluded that the optimum duration of cocoa fermentation is six days, regardless of the variety of the cocoa being fermented. This conclusion is supported by other known information regarding bacteria populations and aroma precursor development.
Hence, as a general rule, it is good practice to ferment cocoa beans for six days. However, the fermenting cocoa beans should be checked at least once a day, and fermentation should cease immediately if signs of over-fermentation appear.
REFERENCES
[1] G.A.R. Wood; R.A. Lass (1985)
"Cocoa - Fourth edition"
Longman Inc., New York
[2] M. Senanayake; E.R. Jansz; K.A. Buckle (1995)
"Effect of variety and location on optimum fermentation requirements of cocoa beans: an aid to fermentation on a cottage scale"
Journal of the Science of Food and Agriculture, Vol.69, issue 4, pp.461-465
Member Marketplace
Share TheChocolateLife
Badge
© 2010 Created by Clay Gordon.
You need to be a member of The Chocolate Life to add comments!
Join The Chocolate Life