Roasting Cocoa, A Little Bit of Magic

Roasting and Chocolate

The techniques used by the chocolate maker to roast the cocoa beans are one of the ways that chocolate makers can bring their own unique artistic vision to their chocolate making. It is one of the most important steps in the process of developing chocolate flavor. Variables such as temperature, the temperature curve (how long the temperature remains at a particular point), the degree of roast, the type of roaster used, and a whole host of other variables are within the chocolate maker’s control, and all make a significant impact on the flavor of the final chocolate.

There is no single “right” way to roast cocoa bean though there are an incredible number of wrong ways. The techniques used by the chocolate maker need to be suited to the types of bean being roasted. Particular attention needs to be given to the size of the bean, its plumpness, the moisture content, the variety, and the bean’s own unique flavor profile and the flavor profile of other beans that will be used during the chocolate-making process. All these must be considered when roasting the bean in order to bring out the bean’s optimal flavor and the best flavor in the final chocolate. There is no single “right way”; the “right way” consists of a series of techniques needed to roast and bring about the optimal flavor profile for the beans being roasted. Unfortunately, most industrial chocolate manufacturers use a series of shortcuts to increase production as well as to reduce labor costs. Roasting cocoa beans properly requires a significant amount of labor, care, and attention to detail, something few chocolate makers are willing to expend.

When most people think of roasting cocoa beans, the first thing they think of is the roasting of coffee. But the roasting of cocoa beans is quite a bit different from the roasting of coffee. For example, coffee is roasted at much higher temperatures than cocoa beans. Cocoa beans are also much more fragile than coffee beans, and if roasted whole and not treated with respect, they are prone to breakage that will likely influence the final flavor profile.

Unlike coffee, which is typically roasted at high temperatures from 380F (195 C) to 480F (250C), cocoa beans must be roasted gently and carefully.. Cocoa beans are sensitive to slight temperature variations—a degree or two in either direction or a few seconds too long or too short is enough to throw off the roast and result in an inferior product. Roasting begins at 210F and typically continues up to 310F. High-speed roasters may roast at temperatures as high as 415 degrees Fahrenheit, though then the roasting time is extremely short—as brief as three minutes.

It is extremely important during roasting that the beans and roast process be very closely monitored. If the beans are over-roasted, there is nothing that may be done to correct the flavor of the resultant chocolate. If the beans are particularly flavorful, such as is the case with criollo and similar varieties, the incredible flavor notes that make them so highly sought after are driven from the beans and up through the chimney into the air outside. While the blocks surrounding the chocolate factory may smell wonderful, the flavor of the beans is ruined. For beans of high quality, a moment of inattention may be a very costly mistake.

When cocoa beans are roasted with the goal of bringing out the best flavors possible, the final phases of the roast are crucially important. It is not uncommon for the cocoa beans to be tasted frequently during this stage. The cocoa beans are removed from the roaster by use of a sampling rod that has a little cup on the end. The rod is inserted into the roaster and used to catch a sampling of beans as they tumble within the roaster. The cocoa beans are crushed and tasted, and the flavor evaluated. This may happen as frequently as every 15 seconds during the last stages of a roast. (This is also about as fast as the artisanal chocolate maker can catch and remove beans, and taste and evaluate the roast.) Surprisingly, the beans should not be pulled from the roaster once the optimal flavor is reached. If they are, they will be over-roasted. The reason is that once the beans are pulled from the roaster, they will continue roasting until their temperature drops below 210 degrees Fahrenheit. This may be as much as 100 degrees below the roast temperature, and roasting happens quickly. To solve this dilemma, the cocoa beans must be removed from the roaster before the peak flavor has been reached. It takes a high degree of skill to determine when this point has been reached so the beans are at the peak of their flavor once they have cooled.

When the beans are unloaded from the roaster, they are cooled on a large cooling table that uses extremely powerful fans to move large volumes of air through the beans to quickly cool them and stop the roasting process. While they are being cooled, the beans are stirred to ensure that they cool quickly and evenly.

Flavor Development in Chocolate

When cocoa beans are roasted, a number of other important chemical changes happen that further influence the process of flavor development.

After the cocoa beans are harvested and removed from their cocoa pods, they are fermented in large fermentation vats. (For more information, be sure to read our article on cocoa bean fermentation.) During the first stage of the fermentation, the yeasts first convert into alcohol the sugars that are in the sweet white placenta that surround each of the beans. When the first stage of fermentation is complete, the yeasts continue and begin to convert the alcohol into acetic acid. (This is the same process that occurs when vinegar is made from wine.) After the fermentation is complete and the beans are dried, much of the acetic acid is left within the bean. The roasting process causes much of the remaining acetic acid to evaporate up the chimney of the roaster. The result is less acidic chocolate more mild in flavor, with less bitterness than chocolate that contains lots of remaining acetic acid.

Another important change that occurs during roasting is the reduction of tannins that are naturally present in the cocoa bean. Tannins are an important part of the cocoa tree’s reproductive system. The sweet placenta that surrounds each bean attracts small animals that burrow into the cocoa pods so they can eat it as a tasty treat. The tannins are very astringent, and this protects the bean from being eaten, along with its sweet surroundings, and the beans are subsequently spread by the animals onto the jungle floor. During the fermentation of cocoa beans, the fermentation destroys many, if not most, of the tannins present. However, if the fermentation is particularly short or inconsistent, tannins will remain, passing their astringent characteristics on to the final chocolate. High temperatures such as those found during the roasting process help destroy the remaining tannins and converts them into tasteless substances called phlobaphenes. The result is a chocolate that is smoother in flavor.

One of the most important changes that occur during roasting is during a process called the Maillard reaction. This reaction is at the heart of almost all roasting and baking. When sugars and some proteins are heated, they break down into simpler forms in a series of reactions that create more complex flavors than are in the original. This is the same set of reactions that can turn table sugar, which has sweet but very neutral flavor, into a wonderfully flavored, complex caramel. As the name implies, the process is named after L. C. Maillard, who first described this process. This process typically changes not only the flavors but also the color, and it as well gives food that has undergone this process a nice brown appearance.

The Maillard reactions are what create the wonderfully flavored coating on the outside of a nicely done steak, the complex flavors in a crust of bread, or the flavored skin of a roasted turkey. Just as the Maillard improves the flavors of meat, bread, and many other baked goods, so too, it develops the complex flavors found in chocolate. The naturally occurring sugars and proteins in the bean break down, creating wonderfully complex flavors in the finished chocolate.

Whole Bean Roasting, Nib Roasting, Cocoa Mass Roasting

Three primary methods are used in the roasting of cocoa beans: whole-bean roasting, nib roasting, and cocoa-mass roasting. Nibs are the bits of the cocoa bean that remain after the husk of the bean has been removed. For a number of reasons, many if not most of the world’s chocolate companies prefer nib roasting or cocoa-mass roasting. The primary one is that when the husks remain on the on the bean during roasting, the naturally occurring cocoa butter within the bean melts, and a significant fraction of it is absorbed into the cocoa bean husk. Since the husk is later removed through a winnowing process, this cocoa butter is unrecoverable and thus wasted. Because cocoa butter is a very expensive ingredient, most manufacturers do all they can to avoid adding additional cocoa butter.

Nib roasting is one of the techniques employed to reduce the need for added cocoa butter, since without the husk, the melted cocoa butter has nowhere to go and is preserved. (Another technique used to reduce the need for additional cocoa butter is the use of lecithin—typically soy lecithin—to reduce the viscosity of the finished chocolate.)

Nib roasting begins with the cocoa beans being quickly heated—similar to roasting, only much faster. This can be done in a continuous roaster, a Micronizer, or potentially even a traditional roaster. When the beans are heated quickly, the cocoa butter and similar fats melt, making the husk pliable. Meanwhile, the water in the beans turns to steam that rapidly expands and separates the husks from the bean by blowing the husk up like a balloon. The beans are then crushed and the husks are removed from the bits of bean through a winnowing process. Here nib roasting benefits the industrial chocolate maker once again. The beans, before they are roasted, are much more flexible, and when they are crushed for winnowing, they are less likely to generate much dust and fine particulates that cannot be recovered.

Some manufacturers who often worki with low quality beans will use this time to alkalize the nibs. The nibs are sprayed with a heated solution of potassium carbonate (also called potash), and the nibs are dried with heated air at or just above the boiling point of water. The alkalization process helps to reduce the acidity and bitterness that are often present in low-quality beans and thus improve their overall flavor.

The nibs are roasted in a traditional or specialized cocoa-bean roaster. Since the nibs are relatively the same size, they roast more uniformly than whole bean roasting, giving the final chocolate a nice, well roasted flavor. In addition, the nibs are smaller than whole beans, so they roast more quickly.

Cocoa-mass roasting, like nib roasting, is partly an effort to conserve cocoa butter to save the large industrial chocolate manufacturers money. Cocoa mass is another name for the paste made from ground up cocoa beans. During nib roasting and whole-bean roasting, the hot gasses of the roaster come into contact with the outsides of the cocoa bean or of nib. This results in the outsides of the beans (or nibs) roasting to a greater degree than the insides. Mass roasting attempts to solve this problem. With mass roasting, the beans are quickly heated to separate the husks from the beans. The beans are crushed into nibs, the nibs are winnowed (the husks removed), and the cocoa nibs are ground into a paste. The paste is then moved into a large heated mixer. The mixer has blades that scrape the sides of the mixer, and the cocoa mass is heated to roasting temperatures for the required period of time. It is also possible for the mass to be roasted by spreading it in a thin film on a large heated cylinder. The heated roller rotates slowly, which gives the cocoa mass time to roast. The roast can be controlled by the temperature of the cylinder as well as the speed at which it rotates. A thin knife blade is used to scrape the roasted film of roasted cocoa mass from off the heated cylinder. While this roasting technique is capable of providing a very consistent and even roast and is relatively fast compared to other roasting styles, the resulting flavor is inferior to whole-bean roasting, which we will cover next.

Artisan chocolate makers typically rely on whole-bean roasting instead of nib roasting or cocoa-mass roasting. Losses must be dealt with, such as the loss of cocoa butter and the loss of a certain percentage of beans to dust and fine particulates. On the other hand, whole-bean roasting generally creates better flavor in the final chocolate than does nib roasting.

Whole-bean roasting, as the name implies, involves roasting the entire bean—husks and all. Whole-bean roasting is the bane of the industrial chocolate makers because of the significant losses of cocoa butter and the raising the manufacturing costs of the final chocolate.

If the cocoa is being roasted for flavor, the cocoa beans are roasted in small quantities, often one or two hundred pounds at a time. Roasting in small quantities makes it is possible to monitor closely the flavor development of the roasting beans and cool the bean quickly when roasting is complete. This is not economical if the manufacturer is trying to make a fifty cent candy bar, because of the high labor costs, loss of cocoa butter, and other factors.

One reason for the superior flavor of whole bean roasting is that the husk helps keep many of the flavorful aromatic oils from evaporating. Admittedly, many of these aromatic oils will eventually be driven off—especially the less flavorful ones—during conching, but even so, keeping them inside the bean at this point results in a better flavored chocolate.

Whole-bean roasting is substantially less complicated than nib roasting, requiring fewer steps as well as less machinery, a roaster being the only machine needed. Sometimes, simpler really is better, and in the case of roasting cocoa beans for flavor, this is true.

Types of Cocoa Bean Roasters

It is not hard to imagine that once in an Olmec village in Central America some cocoa beans were accidentally spilled near the fire, or some genius had the spark of inspiration to roast cocoa beans, an oversight that sent their culture and eventually the rest of the world on the chocolate journey that consumes us like the spark of the fire from that very first roast. In either case, the first cocoa beans were probably roasted on rocks alongside the fire, on a rock slab over the fire, or possibly in a clay pot. Whatever the original method of roasting, it created a legacy that lasts until today.

When cocoa beans were first brought to Europe, the method of roasting was quite simple, often consisting of no more than metal trays suspended by chains over a fire, an ancient Middle Eastern technique for roasting coffee. The beans would be stirred by hand with a long stick or paddle until the roast was complete. Needless to day, this was very labor intensive and inefficient. Clearly, something more efficient was needed.

The next development in roasting technology was not that far distant from roasters in use today. Metal cylinders or balls that could hold up to several pounds of cocoa beans would be suspended over the embers of a fire. A rod would run through the center and act as an axis upon which the roaster would turn. A hand crank on one end would allow the cylinder or ball to be turned while the beans were roasting. The result was a much more even roast than was before possible. Aspects of this technique remain in many of today’s roasters.

Ball Roasters

As mentioned, all roasters were one of the very first kinds of roaster: balls were simply suspended simply over a fire, the cocoa beans inside. Ball roasters remained one of the primary and traditional roasters for cocoa beans through the turn of the century and were constructed at least through the 1960’s. Later designs were pioneered by the company Sirocco. (Sirocco is named after the hot wind that travels up from the Sahara desert and heads north and may reach hurricane speeds by the time it reaches northern Africa, Spain and France.) The ball is encircled within a secondary chamber so that the hot air passes in between the ball and the outer chamber wall. This prevents the flames from impinging directly on the ball and makes it easier to over roast the beans.

Today, ball roasters have been largely replaced by roasters of similar design that use a rotating cylinder rather than a rotating ball. There are a number of practical advantages of this design, since the shape of a cylinder with two ends makes it easier for samples to be removed. It also allows for easier measurement of the temperature of the beans if automation is a requirement. Ball roasters still hold advantage when flavor is of paramount importance.

Fluid Bed Roasters

Fluid bed roasters are a relatively new development. There are a number of different designs, some of them radically different. What they all have in common is that air is blown up through the beans, suspending them at least temporarily in air. The bottom of the roaster may vibrate to help launch the beans into the air. Fluid-bed roasters are typically used in large industrial environments, since they are conducive to short, high-temperature roasting that allows large volumes of beans to be roasted in a short period of time.

Continuous Roasters

The large chocolate manufacturers rely on continuous roasters. Given the quantity of beans that must be roasted for a large industrial chocolate manufacturer and the relatively low prices of industrial chocolate, they are probably one of the only economical ways to roast the large quantity of beans that must be roasted.

There are many different styles of continuous roaster, though in general they fall into two different categories. In one style, the beans are passed on a conveyer belt through a roasting tunnel. The degree of roast can be controlled by controlling the temperature in the tunnel as well as the speed of the conveyer belt. The heat is applied to the beans in a consistent way throughout the roasting process. Alternatively, another style uses a tall tower into which the beans are fed into the top. The tower has a series of trays upon which the beans rest. Once the beans have roasted on one tray for a given period of time, they are dumped onto the next tray. By the time the beans reach the bottom of the tower, they are fully roasted. The airflow through the tower is from the bottom up. The beans cool the air as the air passes them, at the same time heating the beans. This means that the beans on the lower levels are heated faster than those at the top. Because of this, they will generate a different flavor profile in the finished chocolate. It should be pointed out that there are also continuous fluid-bed roasters.

One disadvantage of this kind of roaster is that it is relatively difficult to pull samples of the beans from the roaster while they are being roasted. Furthermore, if the beans are found to be properly roasted when they are only partially through the roaster, there is no way to quickly remove them from the roaster and get them into a cooler. On the other hand, the large industrial chocolate makers run such large quantities of beans, this process can be fine tuned for a particular type of bean. Furthermore, most of these manufacturers use Forestero beans almost exclusively, for which the degree of roast is not as critical as it is with Criollo and other types of high-grade flavor beans.

Cocoa Mass Roasters

These have already been discussed, but to recap, cocoa mass roasters are basically tanks in which the ground cocoa bean paste (cocoa mass) is heated as it is stirred until the desired level of roast is reached. It may also be implemented as a large heated cylinder where the cocoa mass is spread in a thin film. Since the film is thin, it roasts very quickly, and a thin knife blade scrapes it off of the far side of the cylinder. Cocoa-mass roasters are used by the large industrial chocolate manufacturers as a way to quickly roast large quantities of cocoa beans with minimal labor, since it is also a process that by nature requires little labor, and it also lends itself to easy automation.

We won’t get into the many other roasting technologies, such as infrared and microwave. There are even combinations of the various kinds, such as continuous fluid bed roasters. No matter the technology, the best roaster is the one best suited to the job. With poor quality beans, cocoa mass roasters and continuous roasters, or even coffee roasters, will often suffice, since the beans’ flavors are already considerably damaged; no matter the care, the lost flavors may not be brought back. However, if fine flavor is to be developed in the finished chocolate, the choice of roaster is much more critical, as are the techniques used to roast the cocoa beans. Different beans and different styles of chocolate have different roasting requirements, so care must be taken to select the roaster that will best bring the final result, be it high production quantity, as is the case for the large industrial manufacturers, or fine flavor for the artisanal chocolate makers.

Conclusion

Roasting truly is one of the chocolate maker’s arts. It takes a fine flavor palate to be able to judge a roast and judge how the roasted cocoa bean will taste when it is turned into fine chocolate. An incredible number of flavor changes occur during the time the cocoa beans are roasted. Even after the chocolate is complete—even as the chocolate is “resting” and undergoing its final stages of flavor development—the flavors continue to change. The resting process continues oftentimes for several months. The chocolate maker who seeks for optimal flavor must not only think about the flavor of the bean as it is being roasted but must think about how the flavors will change as the chocolate is being made and how the chocolate will taste after it has rested. The flavors will be radically different, and new flavor profiles will often express themselves. Roasting is a bit of a secret art. There are no guidelines on how the best cocoa roasts are to be obtained. It must be learned through experience and through many tests and trials—many of which result in failure. However, this is the case with most all great artistic skills, and the cocoa bean roaster is truly an artist—an artist in flavor. The roaster is an artist who uses one of the world’s greatest sources of flavor and noblest of ingredients—the cocoa bean, also known as “the food of the gods.”