After fermenting your raw cocoa beans, the next step is roasting. In this article, professional chocolatier Simon Knott explains how to roast cacao beans at home, and the science behind cacao roasting.
Cacao roasting is a huge step forward in the flavor development of your cocoa, in preparation for making chocolate. While it is possible to get raw chocolate, for the most part cocoa is roasted, and for good reason. Roasting plays a number of roles, the most important being developing the complex flavor profile of the chocolate we love, through heat-induced reactions such as Strecker degradation and Maillard reaction.
In this article, Simon explains how to roast cacao beans at home using an easy oven-roasting technique, and the science behind why roasting cacao is so desirable.
How to Roast Cacao Beans at Home
By Simon Knott, Professional Chocolatier
Roasting cacao beans at home is a particularly subjective process because cacao beans vary considerably. There can be changes between cacao species in moisture content, size, husk thickness and biochemical makeup, all of which will need different roasting temperatures and duration.
Different roasting temperatures and durations certainly alter the final flavour of beans, but unfortunately, the best formula for your beans can only be arrived at through trial and error. So, the instructions for bean roasting below offer a good general starting point from which you can alter and try out your own experiments.
Cacao Roasting Methods
You can use several techniques to apply heat to cacao beans to roast them:
Oven roasting:
A fan-assisted domestic oven is the most common choice for home-roasting cacao beans, as it is simple, readily available, and the heat is consistent throughout the oven.
Drum roasting:
A metal mesh drum filled with cacao beans is suspended over the hot coals of a BBQ. A metal rod through its centre is turned by hand to tumble and roast the beans over the charcoal.
Coffee roaster:
There are several different types of coffee roasters on the market, but they essentially contain the cacao beans in a perforated drum, which rotates while a fan circulates hot air from a gas or electric heat source. They have variable temperature and duration settings, which can be set on timers.
This video illustrates how to roast cacao beans in a domestic oven.
How to Roast Cacao Beans in an Oven
Equipment
- A domestic fan-assisted oven
- A couple of shallow metal baking trays (those with a perforated insert are ideal as they enable the hot air to circulate underneath the beans during roasting).
Instructions
Spread the beans out in a single layer for oven roasting on a shallow metal tray. Choose beans that are of a similar size and remove any showing signs of mould or that have broken husks. These are more likely to burn, which might affect the flavour of the whole batch.
Cacao Roasting Time and Temperature
Preheat the oven to the first cooking temperature below, then roast cacao as follows:
- Initial hot roast: 5 mins at 300°F (150°C)
- Middle longer roast: 15 mins at 275°F (135°C)
- Final cooler roast: 10 mins at 265°F (130°C)
Put the trays in the oven, and after 20-25 minutes pick out a cacao bean and test it for cocoa aroma, how easy it is to remove the husk and the physical properties of the bean.
How Do You Know When it’s Done?
If the bean is flexible and leathery, it still has too high a water content and needs longer roasting. Taste a small part of the bean for flavour. If it’s slightly under-roasted, it may have more of a fruity taste and need a little longer in the oven. Try different durations and note the differences in flavour and how brittle the bean becomes.
EDITOR’S NOTE: During my visit to the Australian Chocolate Farm, the owner shared perfectly roasted beans with us to inspect. The texture of a perfectly roasted cacao bean has a satisfying crack when you break it with your fingers or your teeth, much like a roasted chickpea. A roasted cocoa bean is not solid like a coffee bean, rather, it has a slight hollowness to it. After roasting, it crumbles when you press it with your fingers, does not flex or bend at all. You can see this in the above picture. -Ayla Marika.
Cacao Roasting Science & Theory
Why Do You Roast Cacao Beans?
- Flavor development
- Kill bacteria with heat, making it food safe
- Roasting improves the texture of chocolate
- Easier to remove husks after roasting cacao, than before
The process of roasting cacao beans transforms them from having a vinegary odour (from the acids produced during cocoa fermentation) to the rich and complex cocoa flavours we love. However, roasting also has several other useful functions. It kills off microorganisms and alters the texture of the beans, which are advantageous when it comes to making chocolate.
After drying, cacao beans still contain about 7% water; roasting must reduce this. If not, the water content will inhibit the emulsification of the cocoa mass and cocoa butter, leading to a grainy rather than a smooth product.
Roasting also alters the texture of the beans and the husks. Drier, more brittle husks are much easier to winnow, while well-roasted beans have a much drier texture, which makes them much better adapted to effective grinding.
During the humidity of fermentation, moulds, other microorganisms and insects can thrive in warm conditions. Bacteria such as E. coli and Salmonella are particularly concerning, being harmful to humans. The heat of roasting serves to destroy any remaining microorganisms.
Warning: The next section is very technical, so if you don’t understand any bits you can skip past them. You can still learn how to roast cacao beans very effectively without knowing the science. For the chocolate geeks, however, please read on to learn more about how roasting cacao assists with chocolate flavor development (some knowledge of food science is helpful).
How Roasting Cacao Improves Flavor & Aroma
- Stecker degradation
- Maillard reaction
- Caramelisation
- Dextrinisation
- Other reactions and compounds
Volatile acids, which are naturally present in cacao beans, can create sour aromas in the final chocolate product. Fortunately, being volatile, the cacao roasting process effectively drives off these acids so they can’t taint the finished product.
The development of flavour, texture, and colour in cacao beans involves many different complex biochemical reactions. Two of the most important in terms of their overall effect on the flavours, textures, and colours of chocolate are Stecker degradation and Maillard reaction.
Strecker degradation
A German chemist, Adolph Strecker, discovered in 1862 that many flavour compounds in foods, including chocolate, were created when amino acids were mostly converted into aldehydes. He named this process Strecker degradation, and it was later shown that peptides and sugars also interact, creating complex flavour molecules such as alcohols, pyrazines, aldehydes, ketones, furans, acids, amines, pyrrols, and esters.
Maillard reaction
In 1912, French medical scientist Louis-Camille Maillard discovered the Maillard reaction, which is fundamental to many of the non-enzymatic browning and flavour-producing reactions which are created when food is cooked. Hundreds of volatile organic compounds are created in the Maillard reaction, which is responsible for food flavours we like the most, such as chocolate, toasting bread, and frying bacon.
What is the Maillard Reaction in Cacao Roasting?
The Maillard reaction is a series of three reactions that do occur slowly at room temperature, but they are most active between 140-165° C (284-329° F), hence their activity during cacao bean roasting.
Before cacao bean roasting, the correct aromatic precursor compounds need to be generated which takes place during fermentation. The polysaccharides and polyphenols present in the cacao, determine the type and quantity of the precursor compounds formed during the fermentation and drying.
In turn, these lead to the formation of specific chocolate aromas in the subsequent roasting process. These polyphenols are released from polyphenolic cells in the bean, and oxidised by the action of the enzyme polyphenol oxidase. This results in reduced bitterness and astringency in the bean and starts the process of browning.
Cacao beans are also naturally rich in catechin, which is a component of cocoa tannins that contribute to bean colour and astringency. Certain amino acids released during fermentation are responsible for the development of Strecker aldehydes (see Strecker degradation) and pyrazines, which are fundamental elements of chocolate flavour.
Lastly, the hydrolysis of anthocyanins during fermentation converts them into more complex molecules. All these reactions and resultant products form the basis of the Maillard reaction during cocoa bean roasting.
In cocoa roasting, the most important Maillard reaction is that between the carbonyl-reducing sugars and the amino group from amino acids or proteins. Aldehydes are generated from the amino acids, which lead to aromatic flavour compounds. At higher roasting temperatures (135 and 150 °C) the Maillard reaction is also responsible for complex chemicals called melanoidins, which determine the brown colouration of the bean. Incidentally, self-tanning products use the Maillard reaction and melanoidins at room temperature to tan skin.
Caramelisation
The caramelisation of sugar is used throughout cooking for the pleasing aromas, nutty flavours, and rich brown colours it produces. When roasting cacao beans the natural carbohydrate content, including sucrose and reducing sugars, is first dehydrated by the heat before undergoing complex reactions.
Caramelisation is separate from the Maillard reaction but has similarities as it is a non-enzymatic browning process. Even today, and despite its widespread use caramelisation is a poorly understood process that is known to involve at least eight different chemical reactions.
The first of these in cacao bean roasting is dehydration, where the applied heat evaporates the water from the sucrose and reducing sugars. This produces furfural in small quantities, which has a strong odour and is widely used in industry.
In addition, the brown colour of caramel is produced by three polymers, caramelans, caramelens and caramelins. At the same time, volatile compounds are created, such as diacetyl, which produces the characteristic nutty caramel flavour.
Dextrinisation
Another non-enzymatic browning reaction associated with roasting cocoa beans is dextrinisation, which works alongside the Maillard reaction. As heat is applied to the beans the starches present are broken down into a series of compounds called dextrins. Dextrins are brown and have a distinctive taste, which adds to the overall bean flavour and colour.
Different dextrins produce different colours and flavours in cacao roasting. For example, when pyrodextrins are produced during toasting bread you can smell the toasted flavour and see the toasted colouration. Toast the bread for too long and you will produce more dextrins associated with the look and taste of burnt toast.
Other Reactions and Compounds
In roasting cacao beans, the following organic chemicals are often included in chocolate’s flavour profile:
- Alcohols: Alcohol is produced during the fermentation of cacao beans. It is mostly driven off during roasting, but a little remains to create sweet and floral chocolate flavours.
- Aldehydes and Ketones: Also produced in small quantities during fermentation, aldehydes and ketones are mostly removed by roasting heat. The remainder are responsible for chocolate flavours and malty, floral, and sweet flavours.
- Pyrazines: For chocolate, pyrazines are the most important organic compound to create flavour in chocolate. The typical flavours we associate with cocoa and cocoa butter are mostly associated with pyrazines, although they also can create spicy, earthy, and nutty flavours. Care must be taken during roasting as a valuable part of chocolate flavour, so they are not excessively driven off.
- Esters: Esters are also important flavour molecules in chocolate. They can be formed from amino acids and the metabolism of yeast. Unroasted beans produce a fruity flavour; in roasted beans, you can expect floral, spicy, and fruity flavours.
- Other: As well as furans, thiazoles, pyrones, acids, imines, amines, oxazoles and pyroles.
Final Tips on How to Roast Cacao beans
We hope you’ve enjoyed this comprehensive article on how to roast cacao beans at home, from chocolatier Simon Knott. If you followed through the whole article, you should now have a good idea of the process for roasting cacao at home and and understanding of the reactions that occur in roasting to develop chocolate flavor, aroma and texture.
In this article, Simon outlined the oven-roasting method, which is achievable for most people at home. After all, almost everyone owns an oven.
Another device you can use as a cacao bean roaster, which I personally have at home, is an air-fryer with a built-in rotisserie drum. I got mine for about $120; it is a versatile machine suitable for all sorts of cooking, and personally one of the best kitchen-appliance investments I’ve made in recent years. Make sure you get an oven-style air-fryer with a rotisserie and turning drum, which is used for cooking fries. The drum can be used as a cacao bean roaster, similar to a coffee roaster.
To learn more techniques on preparing fresh cacao for chocolate-making, make sure to read our article on how to ferment cacao beans at home, which is the fundamental first step in cocoa preparation before roasting. Once you have finished roasting, learn how to make cocoa powder, or continue to follow along with our how to make chocolate bean-to-bar to turn your cacao into finished chocolate.
Happy chocolatiering!
