How the flavour of dark chocolate Develops
This page will be updated as new information is received. Last edited February 18, 2018.
Flavour is often the most important indicator of quality when it comes to chocolate. Although there are many factors which dictate quality, most of these factors overlap with flavour. This section offers you a brief overview of the main determinants of flavour in dark chocolate. This aims to help you understand where the flavours of chocolate originate, and how they develop throughout the process.
This knowledge will allow you to come to your own conclusions about flavour based on informed judgements, and not based on what an expert tells you. Although chocolate experts may have an understanding of what determines flavour, anything beyond that (particularly their judgements) are to some degree subjective, and are not to be regarded as fact. Your own informed decisions and experiences should be the basis for your judgements.
+ What role do genes play in regards to flavour?
First let's try and make sense of the different ways T. cacao is organized. We will discuss variety, cultivar, heirloom, hybrids, and clones. Understanding how genetics affects flavour is easier when we understand the categories associated with genetics.
The species name for our chocolate making tree is Theobroma cacao. Within this species are many varieties. A variety is a wild, genetically unique group within a species.
Over the centuries, there has been a great deal of debate and confusion over the nomenclature of cacao varieties. In the 21st Century, genetic research has brought forth more clarity to how we categorize the different varieties. In 2008, J. C. Motamayor of Mars Inc. published an article that suggested 10 groups or clusters, not varieties, that could be used within the industry (he left it up to others to accept them as varieties). Many have taken on this suggestion and often reference it, some even equating these groups as varieties. The list of ten T. cacao groups or clusters suggested my Motamayor include:
Of course, this is likely not an exhaustive list. As more genetic research and fieldwork pours in, these suggestions will be challenged.
From the varieties come cultivars. A cultivar is a human made (cultivated) variety, either by selecting for traits through natural fertilization (heirloom), physically hand pollinating two types (hybrid), or vegetative, non-sexual reproducing often through grafting (clones).
We're not going to delve into explaining these categories of cultivars, but it's important to be aware of these differences, since the names of varieties, cultivars, and heirlooms often appear on your chocolate bar wrapper, usually as the most prominent feature.
Importance of nomenclature for the consumer
Are these terms important? Do they determine flavour or quality? To the grower and the chocolate maker, they are important. For the grower, understanding and clarifying what genetics they are dealing with helps them sustain high quality cacao. For the maker, choosing flavourful cacao beans is crucial to their work.
However, to the consumer, these terms have more to do with marketing than distinguishing flavour or quality. What a chocolate maker does with the finest heirloom cacao is more important to the flavour than knowing what cacao they are using. Certain varieties become synonymous for quality flavour, and begin to be marketed for the cachet meaning they hold. Although variety and cultivar does affect flavour, it's only one aspect, and shouldn't be the priority in determining your choices.
Let's look at this way. A musician can own the most sought after fiddle on the market, but if they don't execute, if they are not skilled enough, what they create will not do the fiddle justice. Does one listen to music based on what instrument the musician is using, or what music then can create with it? The same goes for chocolate. Genetics (variety, cultivar, etc.) is important, but shouldn't outweigh the many other aspects of the process of chocolate that greatly determine flavour.
That said, genetics is important. The genetics of a tree will affect the flavour of the cacao beans, and the flavour of the cacao beans will impact the flavour of the chocolate.
Much research points to the flavour of the fruit also affecting the flavour of the cacao bean. The flavour of the fruit is associated with the variety or cultivar it grows from.
More flavourful, less acidic fruit surrounding the seeds is said to produce more flavourful and less acidic cacao seeds after fermentation. Some have experimented by adding the fruit of other plant species, and mixing it in with the fermenting cacao seeds. They determined that flavours found within the added fruits were also found within the post fermented cacao beans.
Cacao seeds from the amelonado variety is known to be more astringent due to having a greater amount of bitter polyphenols. Amelonado, which is a variety that was often found under the umbrella term "forastero", was taken from Bahia Brazil to West Africa in the 20th Century, and now makes up the bulk of the cacao grown in the world. It's favorable mostly for yield (larger pods, more seeds, less susceptible to disease), but not often known for quality or flavour.
Criollo is understood to be a variety that was cultivated by the Mesoamericans for centuries if not millennia, and is often much less astringent. It's known to cary many favorable aroma compounds. It's also the most sought after cacao within the fine chocolate industry. It's seen as the finest of the cacao varieties because of the potential aromas one can create with it. However, don't expect all "criollo" made chocolate to taste better than another variety. As well, criollo today is a term used for cacao that is most often not pure criollo, but criollo mixed with another variety such as amelonado.
Nacional is known to be much less astringent as well, often with nutty or fruity notes to it. Nacional boasts cacao with a high ratio of blonde seeds, which make it less astringent as well. It's a variety that was thought to be wiped out from disease, but is now making a comeback.
Other varieties are have not become as mainstream yet, but Maranon is also known to produce very flavourful chocolate as well.
The cultivation of different varieties depends on their demand. The more chocolate makers seek to experiment and use different cultivars, the more likely they are to be worth producing.
Genetically unique trees will metabolize differently, uptake different minerals and interact differently with their environment, which will also impact the flavour of the cacao bean. Not even just within a population, but within individuals that have specific genetic traits. Trees grown within the same plantation will uptake different levels of minerals and nutrients. Not enough research has been done to connect the levels of minerals to the flavour of cacao beans or chocolate, and so we can't yet state that for instance higher amounts of iron will produce a certain flavour. However, from understanding mineral uptake in other species of botanicals, and how that affects flavour, we can begin to look for similar patterns in cacao.
Understand that although genetics is important, there is very little transparency or clarity when it comes to cacao genetics and the flavour of the chocolate bar you are eating. Understand the differences between varieties and cultivars, understand this can affect flavour, but also know that judging your chocolate, good or bad, based on this very misleading. As we will understand later, chocolate is a highly processed food. Not highly processed in the sense of preservative laden and artificial ingredients, but that it goes through many steps until the final product is achieved. Therefore, although the genetics of the tree is the first player in the game of flavour, it's the many steps afterwards which form the final flavour of the chocolate bar. A chocolate should be judged not only on the "variety" but also on other more important factors.
2. Growth & Cultivation
+ Does terroir really affect the flavour of cacao?
It's believed that terroir plays an important role in the flavour of chocolate. Terroir explains the affect the environment (climate, terrain, soil, and interactions with other organisms) has on the characteristics of an organisms during its development, in this case on the cacao bean. Terroir was first used to explain the effect of the environment on the flavour of wine. It wasn't until 1984 that it was used to describe chocolate. It's still not known if terroir carries the same truth for chocolate as it does for wine. Chocolate is not regulated to the same extent as wine, and the definition of terroir for chocolate is often loosely based, and largely unscientific. Bill Nesto (2010) explains this further.
Whatever the degree terroir plays on the final flavour of chocolate, the environment does seem to play a large role in altering the properties of the cacao seed and this is what will be discussed. We know this to be true for other botanicals as well. How much of an impact this has on the final flavour of the chocolate bar requires more research before we make any definite claims.
Geomorphology deals with the terrain, or landscape, the cacao grow in. This can include the altitude, the geology, and surrounding features such as mountains, valleys, and bodies of water. There is not enough research in this area in regards to cacao, but as these features apply to other crops, the same ideas can be applied to cacao, but in what ways specifically remains to be discovered.
The climate alters the metabolism of the tree such as leaf flushing, the amount of flowers it produces, and the number and quality of pods that develop. Climate also affects the properties of cocoa butter, such as the hardness or melting point and the the composition of the fatty acids. Cacao grown in a hot climate will be composed of cocoa butter with a higher melting point than cacao grown in climates not quite as warm. Although climate greatly affects cacao growth, health, and yield, successful links between climate and flavour of the cacao beans have yet to be made.
Soil pH, mineral levels, microbe life, moisture, depth, particle size, will all affect the growth and uptake of nutrients of cacao. However, pretty much all the research to date that deals with soil and cacao relate to yield and growth, and not flavour. We know from other studies, such as on tomatoes, that soil potassium has a logarithmic correlation with the acid content of the tomato (Davies and Winsor, 1967). As well, Increased Nitrogen and Potassium fertilization can have a negative effect on tomato flavour (Wright and Harris, 1985). There are likely similar correlations that can be made for nutrition uptake and cacao fruit and/or seed flavour, but more research is required before making any claims.
Interactions with other organisms
Intercropping T. cacao with shade trees is known to enhance growing conditions such as reducing wind and improving the nutrient cycling (Potassium, carbon, nitrogen) in the soil. As well, it allows the farmers to have a more diverse harvest and help supplement their income. Bai et al. (2017) observed that nutrient uptake in the soil correlated with the types plants intercropped with cacao, as well as their spacing.
It's safe to say that the effect humans have on cultivating their crops will affect the trees growth, and possibly the flavour of the cacao as well. Finding a balance of enough shade, sun, moisture, and nutrients are all aspects the farmers can control to a degree. How much shade they allow will affect how many flowers grow, how much foliage occurs, and the competition these have with the growing cacao pods for nutrients. Although again, not enough research has been made to connect these behaviours of farmers to the flavour of cacao, it's reasonable to assume that there may be a connection between these behaviours and cacao seed or fruit flavour.
+ What does picking cacao pods have to do with flavour?
Time of year & Harvest
Harvesting during one of the two main harvest seasons of the year is said to produce cacao with better tasting fruit. The flavour of the fruit will later have an impact on the flavour of the cacao kernel used to make chocolate.
Picking cacao that is ripe will also affect the final flavour of the fruit, and this is important for the same reason mentioned above. Although there are two main harvests, the harvesting time usually lasts 2-3 months. As well, cacao is an evergreen, and will produce pods throughout the year. For this reason, it takes a great deal of manual labour to sift through the crop often and pick out the ripe pods before they spoil or get taken over by pests. In regions where growers are not paid much for their crop, often in regions where bulk cacao is grown, there is less incentive to wait until optimal ripeness. This may lead to off flavours and high levels of acidity or astringency.
Harvesting is still done by hand. For over 5000 years, cacao is still harvested in a similar manner, with each pod being carefully taken off the tree by hand and cut open one by one. There is no mechanized way to collect cacao pods as there is for some other cash crops. If the seeds are accidentally sliced open, they have to be discarded, as they could mould and develop off flavours that may affect an entire batch of cacao seeds. This care that is required cuts into time and profits, a balance that's not always easy to achieve for some growers.
Pre fermentation preparation
This is the adjustment of the pulp before fermentation (Afoakwa et al., 2011b). Adjusting the level of moisture, the sugar content, the ratio of volume of pulp to seed, and PH will affect the flavour of the cocoa bean. Reducing the sugar content of the pulp has been shown to reduce the level of acids produced, resulting in less acidic beans. (Kongor et al., 2016).
After picking the cocoa pods, they may be stored intact before opening them. Opening them would instantly induce fermentation. Studies have shown that delaying the fermentation of intact pods can reduce the nib acidification when they are finally fermented, as well as increase their cocoa flavour (Kongor et al., 2016).
+ Fermenting for future flavour
Fermentation is the first step in processing that has major implications on the final flavour of chocolate. It's been said that fermentation allows for the precursor molecules of chocolate flavour to develop. Without this step, the flavour of chocolate would not be achieved later during roasting. The most difficult task for the growers is the control of this process. Let's take a look at how different aspects of fermentation affect flavour.
The times vary depending on the preferences of the farmers or those at the fermentation facility. Knowing when to terminate fermentation often depends on experience, learning the smell, appearance, and temperatures of the fermenting mass.
Fermentation duration also depends on the properties of the beans, which often reflect variety and genetics. For instance, criollo often only takes a few days, since these seeds are less astringent. They contain procyanidin, which is a class of flavonoids which make the seeds appear ivory in colour.
"Forastero" on the other hand contains anthocyanins, which don't occur in criollo beans. Anthocyanins are a pigment found in plants that appear red, purple, or blue; likely why unfermented forastero beans appear purple, and why perhaps these beans are considered more astringent and dry as is red wine (which also contains high levels of anthocyanins). They usually take up to a week to ferment.
"Forastero" is used in much of the research on flavonoids instead of the suggested updated categories mentioned above. This research is more likely analyzing Amelonado, but I can't say with certainty.
The correct temperature is important in order for the proper organisms and molecular reactions to occur. Ofteen between 45-50*C. This temperature also kills the germ (or embryo) of the seed.
The Players (organisms):
Multiple species of filamentous fungi, yeasts, lactic acid bacteria, acetic acid bacteria, and Bacillus species are the key players in fermentation of the cacao fruit pulp. Bacteria that are pathogenic and toxigenic haven't been identified during fermentation, probably due to high levels of acetic acid present.
The molds appear to be the first invaders. They, like Bacillus spp. which enter later on, produce the following enzymes:
- proteases (enzymes that breakdown proteins into amino acids and small polypeptides, which are important later during roasting)
- amylases (breaks down carbohydrates into simple sugars),
- and lipases (breaks down fats).
The pulp is rich in sugars (mostly glucose and fructose if ripe, or sucrose if unripe), which also allows yeasts to dominate the process for the first 12-48 hours. Yeasts include Saccharomyces, Candida, and Hanseniaspora to name a few. They perform many jobs including:
- Increasing the pH by removing citric acid
- Produce pectinolytic enzymes to breakdown the pulp, resulting in a more aerobic environment
- Produce ethanol (aids in killing germ)
- Produce organic acids (oxalate, succinate, malate, acetate)
- Produce volatile organic compounds (fusel alcohols, fatty acids, and fatty acid esters) which will later help to create the chocolate aroma
Lactic Acid Bacteria
The first two results of yeast growth allow for the growth of lactic acid bacteria (Lactobacillus, Lactococcus, Leuconostoc). These also produce ethanol.
Acetic Acid Bacteria
Acetic acid bacteria (Acetobacter, Glucono Acetobacter, and Gluconobacter spp.) grow in the last aerobic phase of fermentation. The Acetic acid bacteria oxidize the ethanol produced by the yeasts and LAB into acetate, and then into CO2 and water. Some AAB oxidize lactate. AAB also raises the temperature of the mass to kill the embryo together with the acetic acids and ethanol. If the embryo was allowed to sprout, it would alter and damage the favorable aroma production later on.
Afterwards, Aerobic spore-forming bacteria dominate. The mass becomes less acidic and more aerobic.
Bacillus spp. bacteria produce compounds such as 2,3 butanediol and pyrazines, lactic acid and acetic acids. This adds to the acidity of the seeds, and sometimes results in off flavours. They also produce proteases, amylases, and lipases enzymes as do the filamentous molds.
Now that we know the players, and actions they carry out, we can talk about the products they produce. They essentially break down the proteins and carbohydrates and perform other molecular shifts. Overall, fermentation removes residual pulp from the seeds, kills the embryo, and improves the aroma, flavour, and colour of the bean.
Anthocyanins (polyphenols) rapidly break down to anthocyanidins and sugars (galactose and arabinose) with reductions of up to 93% after 4 days. The anthocyanidins polymerize into tannins, reducing astringency, and decreasing polyphenol content. These reactions continue until too little water inhibits enzymatic actions.
The amounts of theobromine and caffeine are decreased as they diffuse out of the bean.
Proteins are broken down into peptides and amino acids.
It's not only the raw material which dictates quality chocolate, but the types of microorganisms present and their succession within the fermentation which all impact quality. The main beneficial microorganism associated are yeasts, lactic acid bacteria, and acetic acid bacteria. However, these processes are not easily controlled, and so understanding (unravelling which organisms are involved and their roles) it fully with be the first steps in better fermentation control.
Fermented Foods and Beverages of the World, Jyoti Prakash Tamang & Kasipathy Kailasapathy, Taylor and Francis Group, 2010, Boca Raton, FLorida
+ Removing acids and preventing mould
These are the two main goals of drying. Drying allows acids to evaporate and biochemical reactions to occur. As well, it reduces moisture from 40-60% down to 6-7% to help prevent unfavorable moulds.
Drying too slowly after fermentation may cause unwanted mold to develop and would impart off flavours in the cacao beans that may be irreversible. Drying too quickly will cause the seeds to become too acidic. The acidity formed during fermentation is contained under the testa (husk). If dried to quickly, the testa dries up and becomes less permeable, not allowing the acids to evaporate.
Finding that happy medium that releases enough acids and avoiding mold is very important and can have lasting effects on the flavour of the bean. Drying often lasts at least 48 hours.
Sun drying is the most common form of drying in Africa and South America. Cocoa beans are laid out on mats or on pavement. However, they are exposed to animals, wind, and other environmental elements, which increases the risk of contamination.
Wood Burning: In Asia its often too wet, and so wood burning artificial drying is necessary. Wood burning fires direct heat through a chamber which is delivered under the drying platform which holds the beans. However, this often adds a smoky flavour to the beans. You'll notice this more often than not with chocolate made of Indonesian Papua New Guinea beans. The degree of smokiness relates to how much smoke is absorbed by the beans, such as through leaky chambers.
Forced Air: This is a more efficient way of delivering heat while reducing or eliminating the amount of smoke reaching the drying beans.
+ Roasting Forms Flavour
During roasting, reactions take place, including the Maillard Reaction, Strecker Reaction, and caramelization. At temperatures between 120-140*C, most microorganisms (yet not mycotoxins) are killed.
Roasting the beans at high temperatures remove the bitter volatile acids, such as ethanoic acid. Less volatile acids, such as ethanedioic (oxalic) and lactic acids are unchanged by roasting.
As well, the formation of pyrazines (volatile aroma molecules) and their amount depends on the temperature and duration of roasting.
The Maillard Reaction is a "flavour machine" reaction. Hundreds of reactions occur, which result in a browning colour (such as in grilled meats or baked bread) and a complex array of new aroma molecules (particularly baked, toasted, and roasted) that were not there before the reaction. Simply put, it's the marriage of amino acids and reducing sugars (glucose) via heat in the presence of water. Remember fermentation? These amino acids and reducing sugars were created when proteins (12-15%) and carbohydrates were broken down at this stage. Now they are being used to develop new aroma molecules!
Roasting also involves the Strecker Synthesis, which forms aldehydes (aroma molecules) from amino acids (formed during fermentation) and 2-oxopropanal. These aldehydes (and ketones). These reactions also involve the formation of pyrazines, the most important group of aroma molecules found in chocolate.
The characteristic smell of chocolate can also be produced by the reaction of amino acids such as leucine, threonine and glutamine with glucose, when heated to about 1001C. Higher temperatures will produce a much more penetrating/pungent smell.
Polyphenols are molecules often associated with antioxidant activity. There is the debate that processing cacao (fermenting, roasting) eliminates many of these favorable antioxidants. This is the main case for "raw" chocolate. However, although this is true, the process also begins to form new polyphenols, and longer chained ones, that may even have a prolonged affect in our bodies since they take longer to break down. Antioxidants in chocolate have been shown to aid against cardiovascular disease, decrease inflammation, and even improve cognition and/or memory. The types of polyphenols present also affect the bitterness of cacao seeds, and in turn the final flavour of the chocolate.
7. Winnowing & Milling
+ Winnowing to release flavour
Winnowing is the process of removing the testa or "shell" from around the cocoa seed. The cocoa bean is made of the thin permeable outer testa, the kernel which contains proteins, carbohydrates, and fats, and the germ or embryo. The testa is very thin and light. After roasting, the kernel as well as the testa become very brittle. They are crushed together, and then separated by according to their weights. Often air is blown over or used in the form of suction to separate the paper thin testa from the heavier kernel or "nibs" as they are called at this point.
It's been shown that this exposing and breaking up of the nibs allows for a release of acids that were trapped under the testa.
The testa itself also holds residual aroma from the cocoa bean. Today, it's becoming more popular to save the husks, and steep them in the form of a tisane. There is enough flavour contained in them to make a chocolate or cocoa bean tasting tea.
Milling & Melangers
There are a variety of machines to grind chocolate. They grind up the cacao nibs and turn them into a thick paste. After which, the chocolate is sent to a conche to fine tune the flavour.
Many craft chocolate makers today are small scale and use a melanger to mill and fine tune their chocolate all in one machine. They are often composed of a basin with two rolling stone mills. This is more cost effective than using a miller and conche, but they have less control over the balance of texture and flavour in their chocolate.
The other option is to use a mill to grind the cacao and sugar particles to under 30 microns, until our mouth can't detect the particles. Many makers use roll refiners, that pass the chocolate through rollers that move at varying speeds.
The grinding process breaks apart the cell walls of the kernel (cocoa nib), and the heat from grinding begins to warm up the cocoa butter until it liquifies. As this occurs, volatile aromas are being evaporated into the air, specifically the more astringent compounds and acids.
+ Fine tuning in the Swiss Method
The mill does not finish liquefying the chocolate. Therefore, it's transferred to the conche, where it's refined further. This revolutionary machine was invented in 1879 by chocolate maker Rudolf Lindt of Switzerland. His chocolate company was later acquired by another chocolate maker, Chocolat Sprüngli AG, in 1899.
In the 19th Century, mills didn't grind the eating chocolate as smooth as the chocolate we know today, and so his machine did just that. His chocolate was known as the smoothest, silkiest chocolate around. Today, many mills can effectively grind the particles, but the conche also has another function.
The heat and motion involved allows for the astringent and acidic aromas still contained in the chocolate to evaporate out, leaving behind the more favorable aromas a chocolate maker and consumer desires. However, conching too long will allow for many of the aromas to escape, favorable and unfavorable, leaving behind a more one-dimensional tasting chocolate.
The fermentation developed the precursor aroma molecules, the roasting developed the chocolate flavours, and the conche essentially fine tunes the flavour
So what happens? The evaporation of any water left within the chocolate mixture is thought to carry out the acidic aroma molecules with it. As well, the chocolate aromas that are contained within the cocoa butter and cocoa solids, also get transferred to the sugar particles, creating a more homogenous flavour throughout the product. Finally, the viscosity of the chocolate drops, making it more runny and less thick. This is due to the cell walls being broken up, releasing cocoa butter, which in turns coast these broken particles so that they run past each other more smoothly. However, there comes a point when breaking down the particles to small creates too much surface area for the cocoa butter to coat, and it begins to get thick again.
After the chocolate flavour is developed to the makers preference, it is emptied into vessels. Often, but not always, the chocolate is allowed to age. Usually blocks of chocolate are allowed to rest, and it's said that the chocolate mellows out, and any residual harsh aromas dissipate.
+ Beta V: The polymorph of choice
Tempering in a nutshell: Cocoa butter, the fat component of chocolate, crystallizes into 6 different polymorphs. The ideal polymorph for the chocolate bar is Beta V.
What's a polymorph? In chemistry, it specifies a substance (chocolate) that can crystallize into many forms ("Poly" meaning many, and "morph" meaning form). Just as carbon has many polymorphs (diamonds and carbon being two examples, so does cocoa butter. Chocolate (or the fat to be specific) can take on different properties as it solidifies, depending on which of the 6 crystal forms takes prominence.
What does this have to do with flavour? Texture, melt, and flavour release.
If tempered properly (Beta 5 crystallization) the chocolate will take on the form of a shiny, one-toned brown surface, will snap when you break it, and will melt just below body temperature. Other forms can be mottled, whitish, crumbly, with varying melting points; not ideal.
The way the chocolate liquefies in our mouth, and the textures involved, affect our perception of its flavour. If the chocolate is made well, it will have a smooth creamy melt. Off-tempered chocolate (not in the beta V polymorph) will feel more chalky, and take longer to release its flavour, which may also appear more dull.
+ Yes, the way we eat chocolate affects flavour.
It's not as simple as putting it in your mouth and thinking about the aromas. There are tools and techniques that will enhance the satisfaction of our chocolate.
Join a workshop to learn more!