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 theMaillard 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.
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