Chocolate is one of the most popular food items in the world, especially among young children. But before it gets packed in a box, foil, or paper wrapping, it goes through a delicate process. Chocolate is made from dried, fermented cacao beans. Fermentation is the same process that produces flavors in fermented vegetables (such as kimchi) and dairy products (like yogurt). This works by using a beneficial microorganism that converts a carbohydrate into alcohol or acid.
In the case of cacao bean fermentation, lactic acid bacteria (LAB) is one of the major microorganisms involved. Sure, cacao beans are fermented to enhance flavor, making them less astringent and significantly more flavorful than unfermented cacao beans. However, the flavor of fermented cocoa beans is not fully developed yet at this point. Moreover, fermented cocoa beans still have that overpowering vinegary taste and odor from acetic acid. This is because the work of acetic acid bacteria dominates the last phase of fermentation, wherein aeration increases.
You might also like: Chocolate Science: Is Conching Important
To produce the flavor we associate with chocolate, cocoa beans are roasted to produce flavor compounds while driving off the sour‐tasting acetic acid and ethanol. Not only roasting produces flavor, the process also preserves the intrinsic flavors during fermentation.
So happens during the roasting process? There are several physical and chemical changes that take place.
WHAT HAPPENS DURING THE PROCESS?
Roasting involves subjecting the fermented cocoa beans to dry heat at 248°F (120°C) to 320°F (160°C) for 30 minutes up to 60 minutes. The temperature and duration vary, depending on the form of the beans (whole, as nibs or liquor).
The heat used during roasting achieves mainly two things. First is the removal of the undesirable odor and taste. Volatile acids and other substances contribute to bitterness and acidity. Studies have found volatile substances such as aldehydes, ketones, pyrazines, alcohols, and esters. Fats, polyphenols, and alkaloids are compounds that undergo little change during roasting.
You might also like: Chocolate Bloom: What Causes It? Is It Safe?
The degree of changes depends on the roasting time and temperature, as well as the moisture loss during the process. Cocoa beans typically contain 2% final moisture content after roasting. Additionally, the low moisture reduces the number of microorganisms. This allows to produce food-grade products such as cocoa butter and cocoa powder.
The second and main objective of roasting is the activation of the Maillard reaction. In this reaction, the sugars and proteins in the cacao beans yield a complex array of flavor molecules that are linked with the flavor of chocolate. According to numerous studies, cocoa beans produce 200 to 600 flavor molecules during roasting.
Another product of the Maillard reaction is the development of desirable color. This starts to occur during the last part of the reaction. At this point, brown, low molecular weight pigments called melanoidins form, which is also responsible for the color of roasted coffee.
HOW IS IT DONE?
There are 3 methods of roasting cocoa beans: whole bean roasting, nib roasting, and liquor roasting. The form of the cocoa affects the temperature and duration.
Whole bean roasting is the traditional way of producing cocoa liquor (paste produced by grounding cocoa beans). In this method, the beans are first roasted before being winnowed to make it easier to remove the shells, which are cracked by high-impact speed against metal plates. A portion of the cocoa butter is lost as a result of the heat-induced migration of some of the fat into the shells throughout the process. This is especially crucial when dealing with broken or crushed beans.
You might also like: What Is Alkalized Cocoa (Dutch-Processed)?
Many of the drawbacks of roasting whole beans are overcome during nib roasting.. This is because the shells are first removed before roasting. This also makes it possible to roast the nibs while treating them with an alkaline or sugar solution to enhance the flavor of some cocoa varieties.
In liquor roasting, thermal pretreatment is frequently used prior to winnowing. Before roasting, the nib is first ground to liquid. The main drawback of both nib roasting and liquid roasting is that the shell must be removed before it has been heated sufficiently to loosen it from the nib. This can lead to poor separation, especially with some cocoa varieties.
As a result, many different machines have been created for thermal pretreatment of the beans. These provide a high surface temperature that raises the internal moisture to the point where it evaporates, creating pressure inside the bean that separates the shell from the nib.
References:
M. Gibson (2018). Food Science and the Culinary Arts. Academic Press.
E. Afoakwa (2016). Chocolate Science and Technology. John Wiley & Sons, Ltd.
M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding The Biology And Chemistry Behind Food And Cooking. John Wiley & Sons, Inc.
